Patent Publication Number: US-2021169013-A1

Title: Grafting member, grafting member set, holder for grafting, and method for producing graft seedling

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This international application claims priority based on Japanese Patent Application No. 2018-108807 filed on Jun. 6, 2018 in the Japan Patent Office, the entire disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a grafting member, a grafting member set, a holder for grafting, and a method for producing grafted seedlings. 
     BACKGROUND ART 
     Grafting is widely performed in the field of agriculture and horticulture for avoiding replant failure, improving the quality and the yield, and increasing of new varieties, and other purposes. Although grafting is widely spread regardless of whether for business use or home use, grafting is mostly carried out manually. 
     Carrying out the manual grafting requires a certain level of practice; and thus qualities of grafted seedlings tend to vary. For this reason, a seedling nursery member is proposed in which stems of plants germinated from seeds in a chip-shaped member are cut, and units are separated into scion parts and rootstock parts while the cut-off stems are retained (see Patent Document 1). 
     In the seedling nursery member, seedlings for grafting can be prepared in a convenient way, and cut sections of the stems retained in the units can be accurately joined. 
     PRIOR ART DOCUMENTS 
     Patent Documents 
     Patent Document 1: International Patent Publication No. 2016/129683 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the above-described seedling nursery member, the stems of plants are not secured; there is a margin for improvement in positional accuracy of stems to be joined. The above-described seedling nursery member can be still improved in productivity through, for example, sorting of barren individuals, avoidance of contact between roots and the member, and adjustment of height of growing plants. 
     It is desirable that one aspect of the present disclosure provides a grafting member that can achieve improved grafting accuracy and productivity of grafted seedlings. 
     Means for Solving the Problems 
     One aspect of the present disclosure provides a grafting member including a scion part, a rootstock part, a first holder, and a second holder. The scion part includes at least one first contact portion configured to come into contact with a stem of a plant at a first position. The rootstock part is detachable from the scion part. The rootstock part includes at least one second contact portion configured to come into contact with the stem of the plant at a second position located close to roots of the plant as compared with the first position. 
     The first holder is securable to the scion part. The first holder includes at least one first press portion configured to press the stem of the plant against the at least one first contact portion. The second holder is securable to the rootstock part. The second holder includes at least one second press portion configured to press the stem of the plant against the at least one second contact portion. A space is provided between the first holder secured to the scion part and the second holder secured to the rootstock part to expose the stem of the plant. 
     In the above-described configuration, the first contact portion and the first press portion, and the second contact portion and the second press portion enable securing of the stems of the plants respectively in the scion part and the rootstock part in the vicinity of cut sections. Accordingly, positional accuracy of the stems to be joined is improved. As a result, grafting accuracy is improved. 
     Since already-grown plants are used in the grafting member of the present disclosure, it is possible to avoid losses that may be generated, for example, due to barren individuals in a case where seeds are germinated inside the member. It is also possible to avoid the inside of the member being damaged due to growing roots, and avoid the plants being damaged when the roots, biting into the member, are removed from the member. In addition, it is possible to easily and reliably acquire rootstocks with a certain length of hypocotyls. As a result, productivity of grafted seedlings can be improved. 
     Since the size of the member can be easily changed in accordance with the size of the plants in the present disclosure, it is possible to graft various types of plants. Moreover, since one type of the grafting member can be used for both scions and rootstocks, the equipment cost can be reduced. 
     In one aspect of the present disclosure, the at least one first contact portion may include a pair of first receiving surfaces provided at a position where the pair of first receiving surfaces faces the at least one first press portion, and a distance between the pair of first receiving surfaces may decrease along a direction of pressing the first holder. The at least one first press portion may include a pair of first guide surfaces provided at a position where the pair of first guide surfaces faces the at least one first contact portion, and a distance between the pair of first guide surfaces may increase along the direction of pressing the first holder. The at least one second contact portion may include a pair of second receiving surfaces provided at a position where the pair of second receiving surfaces faces the at least one second press portion, and a distance between the pair of second receiving surfaces may decrease along a direction of pressing the second holder. The at least one second press portion may include a pair of second guide surfaces provided at a position where the pair of second guide surfaces faces the at least one second contact portion, and a distance between the second guide surfaces may increase along the direction of pressing the second holder. In the above-described configuration, securing of the first holder and the second holder enables the stem of plant to be guided to and secured at a specified position. 
     In one aspect of the present disclosure, each of the at least one first press portion and the at least one second press portion may include a cushioning material disposed in a connected portion between the pair of first guide surfaces or between the pair of second guide surfaces. In the above-described configuration, it is possible to secure the stems at the specified positions while the difference in diameter of the stems is absorbed by the cushioning materials. 
     In one aspect of the present disclosure, each of the scion part and the rootstock part may include two or more plates provided with the at least one first contact portion or the at least one second contact portion. The two or more plates may include at least one first plate and at least one second plate displaced relative to the at least one first plate in a direction parallel to an axis of the stem of the plant. In the above-described configuration, by having the first holder and the second holder engaged respectively with the first plate and the second plate of the scion part and those of the rootstock part, it is possible to secure the first holder and the second holder without providing securing members for the holders. 
     In one aspect of the present disclosure, the at least one first press portion may include a first cushioning material configured to be deformed by contact of the stem of the plant. The at least one second press portion may include a second cushioning material configured to be deformed by contact of the stem of the plant. In the above-described configuration, the first cushioning material and the second cushioning material can inhibit displacement of the stems. As a result, grafting accuracy is improved. 
     In one aspect of the present disclosure, the at least one first press portion may include a pair of first guide surfaces spaced apart from each other and protruding in a direction of pressing the first holder beyond the first cushioning material, and a distance between the pair of first guide surfaces may increase along the direction of pressing the first holder. The at least one second press portion may include a pair of second guide surfaces spaced apart from each other and protruding in a direction of pressing the second holder beyond the second cushioning material, and a distance between the pair of second guide surfaces may increase along the direction of pressing the second holder. The above-described configuration facilitates to easily and accurately guide the stems of the plants to the first cushioning material and the second cushioning material. 
     In one aspect of the present disclosure, the first cushioning material may be disposed to overlap a part of the pair of first guide surfaces in a direction parallel to an axis of the stem of the plant. The second cushioning material may be disposed to overlap a part of the pair of second guide surfaces in the direction parallel to the axis of the stem of the plant. The above-described configuration facilitates positioning of the first cushioning material and the second cushioning material on the first holder or the second holder. As a result, the first cushioning material and the second cushioning material can be easily replaced. 
     In one aspect of the present disclosure, the first holder may include two or more first press portions as the at least one first press portion, and a first cushioning material structure disposed across the two or more first press portions. The second holder may include two or more second press portions as the at least one second press portion, and second cushioning material structure disposed across the two or more second press portions. The first cushioning material provided to each first press portion of the two or more first press portions may be a part of the first cushioning material structure. The second cushioning material provided to each second press portion of the two or more second press portions may be a part of the second cushioning material structure. In the above-described configuration, it is possible to reduce the number of parts disposed in the holders. As a result, attachment and replacement of cushioning materials can be facilitated. 
     In one aspect of the present disclosure, the at least one first contact portion may include a pair of first receiving surfaces provided at a position where the pair of first receiving surfaces faces the at least one first press portion, and a distance between the pair of first receiving surfaces may decrease along a direction of pressing the first holder. The at least one second contact portion may include a pair of second receiving surfaces provided at a position where the pair of second receiving surfaces faces the at least one second press portion, and a distance between the pair of second receiving surfaces may decrease along a direction of pressing the second holder. In the above-described configuration, securing of the first holder and the second holder enables the stem of plant to be guided to and secured at a specified position. 
     In one aspect of the present disclosure, the at least one first contact portion may include a first protrusion provided in a connected portion between the pair of first receiving surfaces, and the first protrusion may protrude in a direction parallel to an axis of the stem of the plant beyond the pair of first receiving surfaces. The at least one second contact portion may include a second protrusion provided in a connected portion between the pair of second receiving surfaces, and the second protrusion may protrude in the direction parallel to the axis of the stem of the plant beyond the pair of second receiving surfaces. In the above-described configuration, the stem can be easily guided to a securing position between the first contact portion and the first press portion, and between the second contact portion and the second press portion. 
     In one aspect of the present disclosure, a width of the first protrusion, viewed from the direction of pressing the first holder, may decrease with an increase in distance from the pair of first receiving surfaces. A width of the second protrusion, viewed from the direction of pressing the second holder, may decrease with an increase in distance from the pair of second receiving surfaces. The above-described configuration further facilitates guiding of the stem to the securing position. 
     In one aspect of the present disclosure, each pair of the pair of first receiving surfaces and the pair of second receiving surfaces may include a curved portion that is bent in view from a direction parallel to an axis of the stem of the plant. The above-described configuration can inhibit the stem from being damaged when the stem is guided by the first holder and the second holder to the specified position. 
     In one aspect of the present disclosure, each pair of the pair of first receiving surfaces and the pair of second receiving surfaces may further include a flat portion provided in a connected portion of the pair of first receiving surfaces or in a connected portion of the pair of second receiving surfaces. The flat portion may be constituted with a planar surface parallel to the axis of the stem of the plant. The above-described configuration can accurately guide the stem of plant to the specified position by the first holder and the second holder, while inhibiting biting of the stem of the plant. 
     One aspect of the present disclosure may further include a securing mechanism that secures the scion part to the rootstock part. Due to the above-described configuration, a rootstock and a scion after joining can be pressed against each other. As a result, it is possible to inhibit separation between the rootstock and the scion during healing or during transportation. 
     One aspect of the present disclosure may further include a support part configured to support a pod where the roots of the plant are contained. Due to the above-described configuration, the plant can be stably retained during a period before cutting and after joining. 
     In one aspect of the present disclosure, the rootstock part may have a shape that is a mirror image of the scion part with respect to a plane perpendicular to an axis of the stem of the plant. Due to the above-described configuration, the same constituent member can be used for both the scion part and the rootstock part. As a result, the cost of the grafting member can be reduced. 
     Another aspect of the present disclosure provides a grafting member set including a first grafting member and a second grafting member. The first grafting member includes a scion part and a first holder. The scion part includes at least one first contact portion configured to come into contact with a stem of a first plant. The first holder is securable to the scion part, and the first holder includes at least one first press portion configured to press the stem of the first plant against the at least one first contact portion. 
     The second grafting member includes a rootstock part and a second holder. The rootstock part includes at least one second contact portion configured to come into contact with a stem of a second plant. The second holder is securable to the rootstock part, and the second holder includes at least one second press portion configured to press the stem of the second plant against the at least one second contact portion. The scion part of the first grafting member is securable, while the first holder is secured to the scion part, to the rootstock part of the second grafting member while the second holder is secured to the rootstock part. 
     In the above-described configuration, the first holder and the second holder enable securing of the stems of the plants in the vicinity of the cut sections, improving grafting accuracy. Moreover, use of already-grown plants improves productivity of grafted seedlings. 
     Another aspect of the present disclosure provides a holder for grafting. The holder for grafting is secured to at least one of a scion part and a rootstock part, the scion part including at least one first contact portion configured to come into contact with a stem of a plant at a first position, the rootstock part being detachable from the scion part, and the rootstock part including at least one second contact portion configured to come into contact with the stem of the plant at a second position that is close to roots of the plant as compared with the first position. 
     The holder for grafting includes at least one press portion configured to press the stem of the plant against the at least one first contact portion or the at least one second contact portion. The holder for grafting is configured to be secured to the scion part or the rootstock part to provide a space between the first position and the second position to expose the stem of the plant. The at least one press portion includes a cushioning material configured to be deformed by contact of the stem of the plant. 
     Due to the above-described configuration, the holder for grafting is joined with the scion part and the rootstock part configured to retain the plants. This improves grafting accuracy, productivity, and so on as compared to conventional art. 
     Another aspect of the present disclosure provides a method for producing grafted seedling. The method includes: preparing the aforementioned grafting member as a first grafting member, and the aforementioned grafting member as a second grafting member; bringing the at least one first contact portion of the scion part in the first grafting member into contact with a stem of at least a first plant while the rootstock part is attached to the scion part, and bringing the at least one second contact portion of the rootstock part in the first grafting member into contact with the stem of at least the first plant; securing the first holder and the second holder in the first grafting member so as to secure the stem of at least the first plant between the at least one first contact portion and the at least one first press portion and between the at least one second contact portion and the at least one second press portion; cutting the stem of at least the first plant in the space between the first holder and the second holder in the first grafting member; bringing the at least one first contact portion of the scion part in the second grafting member into contact with a stem of at least a second plant while the rootstock part is attached to the scion part, and bringing the at least one second contact portion of the rootstock part in the second grafting member into contact with the stem of at least the second plant; securing the first holder and the second holder in the second grafting member so as to secure the stem of at least the second plant between the at least one first contact portion and the at least one first press portion and between the at least one second contact portion and the at least one second press portion; cutting the stem of at least the second plant in the space between the first holder and the second holder in the second grafting member; and joining a cut surface of the stem of at least the first plant secured by the scion part of the first grafting member and a cut surface of the stem of at least the second plant secured by the rootstock part of the second grafting member. 
     Due to the above-described configuration, grafting accuracy is improved as described above. Productivity of grafted seedlings can be also improved since the already-grown plants are used. Furthermore, grafting can be performed irrespective of the size of plants. Moreover, since one type of the grafting member can be used for both scions and rootstocks, the equipment cost can be reduced. 
     Another aspect of the present disclosure provides a method for producing grafted seedling. The method includes: preparing the first grafting member and the second grafting member of the aforementioned grafting member set; bringing the at least one first contact portion of the scion part in the first grafting member into contact with a stem of at least a first plant; securing the first holder so as to secure the stem of at least the first plant between the at least one first contact portion and the at least one first press portion; cutting the stem of at least the first plant at a position close to roots of at least the first plant as compared with the first holder; bringing the at least one second contact portion of the rootstock part in the second grafting member into contact with a stem of at least a second plant; securing the second holder so as to secure the stem at least the second plant between the at least one second contact portion and the at least one second press portion; cutting the stem of at least the second plant at a position away from the roots of at least the second plant as compared with the second holder; and joining a cut surface of the stem of at least the first plant secured by the scion part of the first grafting member and a cut surface of the stem of at least the second plant secured by the rootstock part of the second grafting member. 
     Due to the above-described configuration, grafting accuracy and productivity of grafted seedlings are improved as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view showing a grafting member in an embodiment. 
         FIG. 2  is a schematic diagram showing a state in which plants are retained in the grafting member in  FIG. 1 . 
         FIG. 3A  is a schematic perspective view showing a scion part of the grafting member in  FIG. 1 ,  FIG. 3B  is a schematic plan view showing the scion part, and  FIG. 3C  is a schematic front view showing of the scion part. 
         FIG. 4A  is a schematic perspective view showing a rootstock part of the grafting member in  FIG. 1 ,  FIG. 4B  is a schematic plan view showing the rootstock part, and  FIG. 4C  is a schematic front view showing of the rootstock part. 
         FIG. 5  is a schematic diagram illustrating a fixing procedure of a first holder and a second holder of the grafting member in  FIG. 1 . 
         FIG. 6A  is a schematic perspective view showing the first holder of the grafting member in  FIG. 1 ,  FIG. 6B  is a schematic plan view showing the first holder, and  FIG. 6C  is a schematic rear view showing of the first holder. 
         FIG. 7  is a schematic perspective view showing the second holder of the grafting member in  FIG. 1 . 
         FIG. 8  is a schematic perspective view showing a support part of the grafting member in  FIG. 1 . 
         FIG. 9  is a schematic perspective view showing a grafting member in an embodiment different from that in  FIG. 1 . 
         FIG. 10A  is a schematic perspective view showing a scion part of the grafting member in  FIG. 9 , and  FIG. 10B  is a schematic front view showing of the scion part. 
         FIG. 11  is a schematic perspective view showing a rootstock part of the grafting member in  FIG. 9 . 
         FIG. 12A  is a schematic perspective view showing a first holder of the grafting member in  FIG. 9 ,  FIG. 12B  is a schematic plan view showing the first holder, and  FIG. 12C  is a schematic rear view showing of the first holder. 
         FIG. 13  is a schematic perspective view showing a second holder of the grafting member in  FIG. 9 . 
         FIG. 14  is a schematic perspective view showing a support part of the grafting member in  FIG. 9 . 
         FIG. 15  is a schematic perspective view showing a grafting member in an embodiment different from those in  FIG. 1  and  FIG. 9 . 
         FIG. 16  is a schematic diagram showing a state in which plants are retained in the grafting member in  FIG. 15 . 
         FIG. 17A  is a schematic perspective view showing a scion part of the grafting member in  FIG. 15 ,  FIG. 17B  is a schematic bottom view showing the scion part, and  FIG. 17C  is a schematic front view showing of the scion part. 
         FIG. 18  is a schematic perspective view showing a rootstock part of the grafting member in  FIG. 15 . 
         FIG. 19  is a schematic diagram illustrating a fixing procedure of a first holder and a second holder of the grafting member in  FIG. 15 . 
         FIG. 20A  is a schematic perspective view showing the first holder of the grafting member in  FIG. 15 ,  FIG. 20B  is a schematic bottom view showing the first holder, and  FIG. 20C  is a schematic rear view showing of the first holder. 
         FIG. 21A  is a schematic partial enlarged view showing a press portion in an embodiment different from that in  FIG. 20A , and  FIG. 21B  is a schematic partial enlarged view showing the press portion in an embodiment different from those in  FIG. 20A  and  FIG. 21A . 
         FIG. 22  is a schematic perspective view showing the second holder of the grafting member in  FIG. 15 . 
         FIG. 23  is a schematic perspective view showing a support part of the grafting member in  FIG. 15 . 
         FIG. 24  is a schematic perspective view showing a grafting member in an embodiment different from those in  FIG. 1 ,  FIG. 9 , and  FIG. 15 . 
         FIG. 25A  is a schematic perspective view showing a scion part of the grafting member in  FIG. 24 ,  FIG. 25B  is a schematic bottom view showing the scion part, and  FIG. 25C  is a schematic front view showing of the scion part. 
         FIG. 26A  is a schematic perspective view showing a first holder of the grafting member in  FIG. 24 ,  FIG. 26B  is a schematic bottom view showing the first holder, and  FIG. 26C  is a schematic rear view showing of the first holder. 
         FIG. 27  is a flowchart illustrating a method for producing grafted seedlings in an embodiment. 
         FIG. 28  is a schematic perspective view showing a grafting member set in an embodiment. 
         FIG. 29  is a schematic perspective view showing a second frame of a first grafting member in  FIG. 28 . 
     
    
    
     EXPLANATION OF REFERENCE NUMERALS 
       1 ,  10 ,  101 ,  201  . . . grafting member,  2 ,  12 ,  102 ,  202  . . . scion part,  3 ,  13 ,  103 ,  203  . . . rootstock part,  4 ,  14 ,  104 ,  204  . . . first holder,  5 ,  15 ,  105 ,  205  . . . second holder,  6 ,  16 ,  106 ,  206  . . . support part,  24 ,  24 A,  24 B,  124 ,  224  . . . first contact portion,  25 A,  25 B,  125 A,  125 B,  225 A,  225 B . . . first receiving surface,  34 ,  34 A,  34 B,  134  . . . second contact portion,  35 A,  35 B,  135 A,  135 B . . . second receiving surface,  41 ,  41 A,  41 B,  141 ,  241  . . . first press portion,  42 A,  42 B,  142 A,  142 B,  242 A,  242 B . . . first guide surface ,  42 C,  52 C,  142 C,  152 C,  242 C . . . cushioning material,  51 ,  51 A,  51 B,  151  . . . second press portion,  52 A,  52 B,  152 A,  152 B . . . second guide surface. 
     MODE FOR CARRYING OUT THE INVENTION 
     The following describes, with reference to the drawings, embodiments to which the present disclosure is applied. 
     1. First Embodiment 
     [1-1. Configuration] 
     A grafting member  1  shown in  FIG. 1  is a cassette type member for cutting plants and acquiring scions and rootstocks and for joining the acquired scions and rootstocks. 
     The grafting member  1  in  FIG. 1  is configured such that the grafting member  1  can be used as a first grafting member to acquire scions and as a second grafting member to acquire rootstocks. Specifically, a grafting member set of the present embodiment comprises the grafting member  1  as the first grafting member and the grafting member  1  as the second grafting member. 
     The grafting member  1  as the first grafting member and the grafting member  1  as the second grafting member do not have to have exactly the same shape. In other words, the second grafting member may have a part that is shaped differently from the first grafting member. 
     The grafting member  1  comprises a scion part  2 , a rootstock part  3 , a first holder  4 , a second holder  5 , and a support part  6 . Although  FIG. 1  shows a state in which these components are assembled, each component is configured to be detachable. Each component, except magnets and cushioning materials which will be described later, may be formed of, for example, resin, metal, or other materials. 
     As shown in  FIG. 2 , the grafting member  1  is configured to be capable of retaining plants P inside thereof. Although five plants P are retained in  FIG. 2 , the number of the plants P retained in the grafting member  1  is not limited to five. In addition, the type of plants P is not particularly limited. 
     &lt;Scion Part&gt; 
     As shown in  FIG. 3A , the scion part  2  has a first lower plate  21 , a first upper plate  22 , and a first frame  23 . 
     The first lower plate  21  is a plate-shaped portion having a plate surface parallel to a direction I of pressing (that is, a direction of inserting) the first holder  4 , which will be described later, and perpendicular to the axes of the plants P. The first lower plate  21  have first contact portions  24  that come into contact with the respective stems of the plants P at a first position P 1  (see  FIG. 2 ). The first position P 1  is located close to the tips (that is, the stem tips) of the plants P as compared with a cut position of the plants P. 
     The first contact portions  24  and first press portions  41  of the first holder  4  (see  FIG. 6A ) interpose the stems of the plants P therebetween to secure the stems of plants P. The first contact portions  24  are recesses provided to the first lower plate  21 . The first contact portions  24  are arranged in parallel in a direction intersecting the direction I of pressing the first holder  4 . Each first contact portion  24  has a pair of first receiving surfaces  25 A,  25 B and a first protrusion  26 . 
     The pair of first receiving surfaces  25 A,  25 B is provided at a position where the pair of first receiving surfaces  25 A,  25 B faces the first press portion  41  of the first holder  4  attached to the scion part  2 , and the distance between the pair of first receiving surfaces  25 A,  25 B decreases along the direction I of pressing the first holder  4 . In other words, the first contact portions  24  are recesses that are open to the outside of the first lower plate  21 . As shown in  FIG. 3B , the pair of first receiving surfaces  25 A,  25 B has a shape of a curved line that is bent smoothly when viewed from a direction parallel to the axis of the stem of the plant P (hereinafter also referred to as a “plant P axis direction”). The edges of the pair of first receiving surfaces  25 A,  25 B in the plant P axis direction are chamfered. The axes of the stems of the plants P are, for example, parallel to the vertical direction. 
     As shown in  FIG. 3A , a first protrusion  26  is provided in a connected portion  25 C of the pair of first receiving surfaces  25 A,  25 B (that is, in the innermost part of the first contact portion  24 ), and the first protrusion  26  protrudes in the plant P axis direction beyond the first receiving surfaces  25 A,  25 B. Specifically, the first protrusion  26  is raised from the upper surface of the first lower plate  21  in a direction toward the tip of the plant P. 
     As shown in  FIG. 3C , the width of the first protrusions  26  when viewed in the direction I of pressing the first holder  4  decreases with the distance from the first receiving surfaces  25 A,  25 B (that is, toward the tips). 
     As shown in  FIG. 3A , the first upper plate  22  is disposed in parallel to the first lower plate  21  to be spaced apart from the first lower plate  21 . The first upper plate  22  is disposed close to the tips of the plants P as compared with the first lower plate  21 . The first upper plate  22  has recesses  22 A for insertion of the plants P. Each recess  22 A is provided at a position to be aligned with the first contact portion  24  when viewed in the plant P axis direction. 
     The first lower plate  21  and the first upper plate  22  are coupled by the first frame  23  and columnar portions  29 . Between the first lower plate  21  and the first upper plate  22 , a slit-like space is formed for insertion of the first holder  4 . The first frame  23  has guide grooves  23 A,  23 B that guide the first holder  4 . 
     The columnar portions  29  are each disposed between adjacent first contact portions  24  (that is, between the first receiving surface  25 A of one first contact portion  24  and the first receiving surface  25 B of another first contact portion  24  adjacent to the former first contact portion  24 ). The columnar portions  29  each have guide grooves  29 A that guide the first holder  4 . 
     The first frame  23  has two first main magnets  27 A,  27 B that serve as a securing mechanism to detachably secure the scion part  2  and the rootstock part  3 . The two first main magnets  27 A,  27 B are disposed where the two first main magnets  27 A,  27 B face and abut the rootstock part  3  (specifically, on the bottom surface of the first frame  23 ), and are connected to the respective second main magnets  37 A,  37 B of the rootstock part  3 . 
     The first frame  23  also has two first auxiliary magnets  28 A,  28 B that serve as a securing mechanism to detachably secure the scion part  2  and the first holder  4 . The two first auxiliary magnets  28 A,  28 B are disposed where the two first auxiliary magnets  28 A,  28 B face and abut the first holder  4  (specifically, on the lateral surfaces of the first frame  23 ), and are connected to the respective opposite magnets  45 A,  45 B of the first holder  4 . 
     The scion part  2  of the grafting member  1  as the first grafting member is configured to be attachable, while the first holder  4  is secured thereto, to the rootstock part  3  of the grafting member  1  as the second grafting member to which the second holder  5  is secured. 
     &lt;Rootstock Part&gt; 
     As shown in  FIG. 4A , the rootstock part  3  has a second upper plate  31 , a second lower plate  32 , and a second frame  33 . 
     The second upper plate  31  is a plate-shaped portion having a plate surface parallel to a direction I of pressing the second holder  5 , which will be described later, and perpendicular to the axes of the stems of the plants P. The second upper plate  31  has second contact portions  34  that come into contact with the respective stems of the plants P at a second position P 2  (see  FIG. 2 ). The second position P 2  is located close to the roots of the plants P as compared with the cut position of the plants P. 
     The second contact portions  34  and second press portions  51  of the second holder  5  (see  FIG. 7 ) interpose the stems of the plants P therebetween to secure the stems of plants P. The second contact portions  34  are recesses provided to the second upper plate  31 . The second contact portions  34  are arranged in parallel in a direction intersecting the direction I of pressing the second holder  5 . Each second contact portion  34  has a pair of second receiving surfaces  35 A,  35 B and a second protrusion  36 . 
     The pair of second receiving surfaces  35 A,  35 B is provided at a position where the pair of second receiving surfaces  35 A,  35 B faces the second press portion  51  of the second holder  5  attached to the rootstock part  3 , and the distance between the pair of second receiving surfaces  35 A,  35 B decreases along the direction I of pressing the second holder  5 . In other words, the second contact portions  34  are recesses that are open to the outside of the second upper plate  31 . As shown in  FIG. 4B , the pair of second receiving surfaces  35 A,  35 B has a shape of a curved line that is bent smoothly when viewed from the plant P axis direction. The edges of the pair of second receiving surfaces  35 A,  35 B in the plant P axis direction are chamfered. 
     As shown in  FIG. 4A , a second protrusion  36  is provided in a connected portion  35 C of the pair of second receiving surfaces  35 A,  35 B (that is, in the innermost part of the second contact portion  34 ), and the second protrusion  36  protrudes in the plant P axis direction beyond the second receiving surfaces  35 A,  35 B. Specifically, the second protrusion  36  is raised from the bottom surface of the second upper plate  31  in a direction toward the tip of the plant P. 
     As shown in  FIG. 4C , the width of the second protrusions  36  when viewed in the direction I of pressing the second holder  5  decreases with an increase in distance from the second receiving surfaces  35 A,  35 B (that is, toward the tips). 
     Each second contact portion  34  is arranged at a position to be aligned with the corresponding first contact portion  24  while the scion part  2  and the rootstock part  3  are secured. In the present embodiment, the second contact portions  34  have a shape of the first contact portions  24  inverted in the plant P axis direction. In other words, the second contact portions  34  are identical to the first contact portions  24  except that the orientation of the first protrusions  26  is inversed. The second contact portions  34  and the first contact portions  24 , thus, have the same shape in a planar view (specifically, when viewed in the plant P axis direction). However, the shape of the second contact portions  34  and the first contact portions  24  in a planar view may be different, and the second protrusion  36  of the second contact portion  34  and the first protrusion  26  of the first contact portion  24  may be raised in the same direction. 
     As shown in  FIG. 4A , the second lower plate  32  is disposed in parallel to the second upper plate  31  to be spaced apart from the second upper plate  31 . The second lower plate  32  is disposed close to the roots of the plants P as compared with the second upper plate  31 . The second lower plate  32  has recesses  32 A for insertion of the plants P. Each recess  32 A is provided at a position to be aligned with the second contact portion  34  when viewed in the plant P axis direction. 
     The second upper plate  31  and the second lower plate  32  are coupled by the second frame  33  and columnar portions  39 . Between the second upper plate  31  and the second lower plate  32 , a slit-like space is formed for insertion of the second holder  5 . The second frame  33  has guide grooves  33 A,  33 B that guide the second holder  5 . 
     The columnar portions  39  are each disposed between adjacent second contact portions  34  (that is, between the second receiving surface  35 A of one second contact portion  34  and the second receiving surface  35 B of another second contact portion  34  adjacent to the former second contact portion  34 ). The columnar portions  39  each have guide grooves  39 A that guide the second holder  5 . 
     The second frame  33  supports the scion part  2 . The second frame  33  has four second main magnets  37 A,  37 B,  37 C,  37 D that serve as a securing mechanism to detachably secure the scion part  2  and the support part  6 , which will be described later, to the rootstock part  3 . 
     The two second main magnets  37 A,  37 B are disposed where the two second main magnets  37 A,  37 B face and abut the scion part  2  (specifically, the upper surface of the second frame  33 ), and are connected to the respective first main magnets  27 A,  27 B of the scion part  2 . The remaining two second main magnets  37 C,  37 D are disposed where the two second main magnets  37 C,  37 D face and abut the support part  6  (specifically, on the bottom surface of the second frame  33 ), and are connected to the respective third main magnets  63 A,  63 B of the support part  6 . 
     The second frame  33  also has two second auxiliary magnets  38 A,  38 B that serve as a securing mechanism to detachably secure the second holder  5  to the rootstock part  3 . The two second auxiliary magnets  38 A,  38 B are disposed where the two second auxiliary magnets  38 A,  38 B face and abut the second holder  5  (specifically, the lateral surfaces of the second frame  33 ), and are connected to the respective opposite magnets  55 A,  55 B of the second holder  5 . 
     It is preferable that the two first auxiliary magnets  28 A,  28 B of the scion unit  2  are arranged in a manner so that the magnetic poles thereof are different from those of the two second auxiliary magnets  38 A,  38 B of the rootstock unit  3  stacked in the up-down direction. For example, it is preferable that the south pole of the second auxiliary magnet  38 A is arranged in relation to the north pole of the first auxiliary magnet  28 A, and north pole of the second auxiliary magnet  38 B is arranged in relation to the south pole of the first auxiliary magnet  28 A. This arrangement inhibits removal of the scion part  2  from the rootstock part  3  due to repulsion of magnets. 
     &lt;First Holder&gt; 
     As shown in  FIG. 5 , the first holder  4  is a plate-shaped member configured such that it can be secured to the scion part  2 . In the present embodiment, the first holder  4  is inserted in the horizontal direction between the first lower plate  21  and the first upper plate  22  of the scion part  2 . Accordingly, the first holder  4  is secured to the scion part  2 . 
     As shown in  FIG. 6A , the first holder  4  has the first press portions  41  that press the respective stems of the plants P against first contact portions  24  of the scion part  2 . The first press portions  41  are arranged at positions where the first press portions  41  face the first contact portions  24  in the direction I of pressing the first holder  4 . 
     The first press portions  41  correspond to recesses forming a portion with a comb teeth shape in the first holder  4 , and are arranged in parallel in a direction intersecting the direction I of pressing the first holder  4 . Each first press portion  41  has a pair of first guide surfaces  42 A,  42 B and a cushioning material  42 C. 
     The pair of first guide surfaces  42 A,  42 B is provided at a position where the pair of first guide surfaces  42 A,  42 B faces the first contact portion  24  of the scion part  2 , and the distance between the pair of first guide surfaces  42 A,  42 B increases along the direction I of pressing the first holder  4 . In other words, the first press portions  41  are recesses that are open to the outside of the first holder  4 . As shown in  FIG. 6B , the pair of first guide surfaces  42 A,  42 B has a shape of a curved line that is bent smoothly when viewed from the plant P axis direction. The edges of the pair of first guide surfaces  42 A,  42 B in the plant P axis direction are chamfered. 
     The cushioning material  42 C is disposed in a connected portion of the pair of first guide surfaces  42 A,  42 B (that is, in the innermost part of the first press portion  41 ). The cushioning material  42 C is made of a material that can be deformed to a certain extent by contact of the stem of the plant P. Examples of the material forming the cushioning material  42 C include porous materials such as sponges. Elastic materials, such as rubber, may be also used for the material forming the cushioning material  42 C. 
     The stem of the plant P placed in the first contact portion  24  is brought into contact with the cushioning material  42 C of the first press portion  41  and the first protrusion  26  of the first contact portion  24 . The stem of the plant P is retained between the first contact portion  24  and the first press portion  41 , thus being inhibited from moving in the direction of the diameter of the stem. 
     As shown in  FIGS. 6B and 6C , the first holder  4  has bulging portions  43  that are in contact with the cushioning materials  42 C and bulge out in the plant P axis direction beyond the first press portion  41 . The first holder  4  is inserted into the scion part  2  such that the surface provided with the bulging portions  43  faces toward the roots of the plants P (specifically, becomes the bottom surface). 
     The first holder  4  has slits  44  provided between the first press portions  41 . When the first holder  4  is inserted into the scion part  2 , each columnar portion  29  of the scion part  2  is inserted into each slit  44 . 
     The first holder  4  also has two magnets  45 A,  45 B that serve as a securing mechanism to detachably secure the first holder  4  to the scion part  2 . The two magnets  45 A,  45 B are disposed where the magnets  45 A,  45 B face and abut the first frame  23 , and are connected to the respective opposite first auxiliary magnets  28 A,  28 B of the first frame  23 . 
     &lt;Second Holder&gt; 
     As shown in  FIG. 5 , the second holder  5  is a plate-shaped member configured such that it can be secured to the rootstock part  3 . In the present embodiment, the second holder  5  is inserted in the horizontal direction between the second upper plate  31  and the second lower plate  32  of the rootstock part  3 . Accordingly, the second holder  5  is secured to the rootstock part  3 . 
     As shown in  FIG. 7 , the second holder  5  has the second press portions  51  that press the respective stems of the plants P against the second contact portions  34  of the rootstock part  3 . The second press portions  51  are arranged at positions where the second press portions  51  face the second contact portions  34  in the direction I of pressing the second holder  5 . 
     Each second press portion  51  has a pair of second guide surfaces  52 A,  52 B and a cushioning material  52 C. The pair of second guide surfaces  52 A,  52 B is provided at a position where the pair of second guide surfaces  52 A,  52 B faces the second contact portion  34  of the rootstock part  3 , and the distance between the pair of second guide surfaces  52 A,  52 B increases along the direction I of pressing the second holder  5 . In other words, the second press portions  51  are recesses that are open to the outside of the second holder  5 . The pair of second guide surfaces  52 A,  52 B has a shape of a curved line that is bent smoothly when viewed from the plant P axis direction. 
     The cushioning materials  52 C are identical to the cushioning materials  42 C of the first press portions  41  of the first holder  4 ; the description of which, thus, will be omitted. 
     In the present embodiment, the second holder  5  is a mirror image of the first holder  4  with respect to a plane perpendicular to axes of the stems of the plants P (specifically, a horizontal plane). In other words, the second holder  5  is a vertical inversion of the first holder  4 . The second holder  5 , however, may have a portion partly different from the first holder  4 . 
     The second holder  5  has bulging portions  53 , slits  54 , and the two magnets  55 A,  55 B. The bulging portions  53  and the slits  54  are identical to the bulging portions  43  and the slits  44  of the first holder  4 ; the description of which, thus, will be omitted. The second holder  5  is inserted into the rootstock part  3  such that the surface provided with the bulging portions  53  faces toward the tips of the plants P (specifically, becomes the upper surface). 
     The two magnets  55 A,  55 B are a securing mechanism to detachably secure the second holder  5  to the rootstock part  3 . The two magnets  55 A,  55 B are disposed where the magnets  55 A,  55 B face and abut the second frame  33  of the rootstock part  3 , and are connected to the respective opposite second auxiliary magnets  38 A,  38 B of the second frame  33 . 
     As shown in  FIG. 1 , a space S is provided between the first holder  4 , secured to the scion part  2 , and the second holder  5 , secured to the rootstock part  3 , to expose the stems of the plants P. In other words, the first holder  4  and the second holder  5 , by being respectively secured to the scion part  2  and the rootstock part  3 , provide the space S to expose the stems of the plants P between the first position P 1  and the second position P 2 . The stems are cut in the space S to acquire scions and rootstocks of the plants P. 
     &lt;Support Part&gt; 
     As shown in  FIG. 2 , the support part  6  supports pods Q in which the roots of the plants P are contained. 
     As shown in  FIG. 8 , the support part  6  has a body  61 , support frames  62 , and two third main magnets  63 A,  63 B. In the present embodiment, the support part  6  is configured to be detachable from the rootstock part  3 . 
     The body  61  is provided with an internal space into which the pods Q can be inserted. The support frames  62  catch the respective pods Q in the vertical direction and protrude inward from the inner wall of the body  61 . 
     The two third main magnets  63 A,  63 B are disposed where the two third main magnets  63 A,  63 B face and abut the rootstock part  3  (specifically, the upper surface of the body  61 ), and are connected to the respective second main magnets  37 C,  37 D of the rootstock part  3 . 
     [1-2. Effects] 
     The embodiments described hereinabove in detail achieve the following effects. 
     (1a) The first contact portions  24  and the first press portions  41 , and the second contact portions  34  and the second press portions  51  enable securing of the stems of the plants P respectively in the scion part  2  and the rootstock part  3  at two positions, namely at the upper position and the lower position, in the vicinity of cut sections. Accordingly, the positional accuracy of the stems to be joined is improved. As a result, grafting accuracy is improved. 
     (1b) Since already-grown plants P are used, it is possible to avoid losses that may be generated, for example, due to barren individuals in a case where seeds are germinated inside the member. It is also possible to avoid the inside of the member being damaged due to growing roots, and avoid the plants P being damaged when the roots, biting into the member, are removed from the member. In addition, it is possible to easily and reliably acquire rootstocks with a certain length of hypocotyls. As a result, productivity of grafted seedlings can be improved. 
     (1c) Since the size of the member can be easily changed in accordance with the size of the plants P, it is possible to graft various types of plants. Moreover, since one type of the grafting member  1  can be used for both scions and rootstocks, the equipment cost can be reduced. 
     (1d) The distance between the pair of first receiving surfaces  25 A,  25 B and the distance between the pair of second receiving surfaces  35 A,  35 B decrease along the direction of pressing the holders, while the distance between the pair of first guide surfaces  42 A,  42 B and the distance between the pair of second guide surfaces  52 A,  52 B increase along the direction of pressing the holders. Accordingly, by insertion of the first holder  4  and the second holder  5 , the stems of the plants P can be easily and accurately guided to and secured at specified positions. 
     (1e) The width of the first protrusions  26  and the width of the second protrusions  36  viewed from the direction of pressing the holders decrease with an increase in distance respectively from the pair of first receiving surfaces  25 A,  25 B and the second receiving surfaces  35 A,  35 B. Accordingly, the stems can be easily guided to securing positions between the first contact portions  24  and the first press portions  41 , and between the second contact portions  34  and the second press portions  51 . 
     (1f) Each pair of first receiving surfaces  25 A,  25 B, first guide surfaces  42 A,  42 B, second receiving surfaces  35 A,  35 B, and second guide surfaces  52 A,  52 B has the shape of a curved line that is bent when viewed from the plant P axis direction. Accordingly, it is possible to inhibit the stems from being damaged when the first holder  4  and the second holder  5  are inserted to guide the stems to the specified positions. 
     (1g) Since the first press portions  41  and the second press portions  51  respectively have the cushioning materials  42 C,  52 C, it is possible to secure the stems at the specified positions while the difference in diameter of the stems is absorbed by the cushioning materials  42 C,  52 C. 
     (1h) Due to the securing mechanisms made up of the first main magnets  27 A,  27 B and the second main magnets  37 A,  37 B, rootstocks and scions after joining can be pressed against each other. As a result, it is possible to inhibit separation between the rootstocks and the scions during healing or during transportation. 
     (1i) Due to the support part  6  that supports the pods Q with the roots of the plants P contained therein, the plants P can be stably retained during a period before cutting and after joining. 
     2. Second Embodiment 
     [2-1. Configuration]Similarly to the grafting member  1 , a grafting member  10  shown in  FIG. 9  is configured such that the grafting member  10  can be used as the first grafting member so as to acquire scions and also as the second grafting member so as to acquire rootstocks. 
     The grafting member  10  comprises a scion part  12 , a rootstock part  13 , a first holder  14 , a second holder  15 , and a support part  16 .  FIG. 9  shows an assembled state of these components; each of the components however is configured to be detachable. Each component, except magnets and cushioning materials which will be described later, may be formed of, for example, resin, metal, or other materials. 
     &lt;Scion Part&gt; 
     As shown in  FIGS. 10A and 10B , the scion part  12  has two first plates  21 A, one second plate  21 B, and a first frame  23 . 
     The first plates  21 A and the second plate  21 B are plate-shaped portions, each having a plate surface parallel to a direction I of pressing the first holder  14 , which will be described later. The first plates  21 A and the second plate  21 B are arranged in parallel in a direction intersecting the direction I of pressing stems of plants P. The second plate  21 B is interposed between the two first plates  21 A. The two first plates  21 A are each provided with a downward-facing first contact portion  24 A. The second plate  21 B is provided with upward-facing first contact portions  24 B. 
     The first contact portions  24 A,  24 B are identical to the first contact portions  24  of the scion part  2  in  FIG. 3A . Specifically, each of the first contact portions  24 A,  24 B has a pair of first receiving surfaces  25 A,  25 B and a first protrusion  26  provided in a connected portion  25 C of the pair of first receiving surfaces  25 A,  25 B. 
     In the present embodiment, the first protrusions  26  of the downward-facing first contact portion  24 A provided to the first plates  21 A are raised from the bottom surfaces of the first plates  21 A (that is, from the plate surfaces on the rootstock part  13  side) in a direction toward the roots of the plants P. 
     The first protrusions  26  of the upward-facing first contact portion  24 B, interposed between the two downward-facing first contact portions  24 A, are raised from the upper surface of the second plate  21 B (that is, from the plate surface on the opposite side of the rootstock part  13  side) in a direction toward the tips of the plants P. 
     As described above, the scion part  12  has the downward-facing first contact portions  24 A and the upward-facing first contact portion  24 B with the respective first protrusions  26  protruding in directions different from each other. The downward-facing first contact portions  24 A do not have to be arranged at both ends of the scion part  12 . Moreover, the scion part  12  may have one downward-facing first contact portion  24 A. Similarly, the scion part  12  may have one upward-facing first contact portion  24 B. 
     As shown in  FIG. 10B , the lower surfaces of the first plates  21 A are arranged at the same position as that of the upper surface of the second plate  21 B in the plant P axis direction, or at a position close to the tips of the plants P compared with the upper surface of the second plate  21 B. In other words, the second plate  21 B is displaced relative to the first plates  21 A in a direction parallel to the stems of the plants P. 
     Between the two first plates  21 A and the second plate  21 B, respective slits  23 C,  23 D are formed to guide insertion of the first holder  14 . 
     Similarly to the first frame  23  of the scion part  2  in  FIG. 3A , the first frame  23  has two first main magnets (not shown) that serve as a securing mechanism to detachably secure the scion part  12  and the rootstock part  13 , and two first auxiliary magnet  28 A,  28 B that serve as a securing mechanism to detachably secure the first holder  14  to the scion part  12 . 
     &lt;Rootstock Part&gt; 
     As shown in  FIG. 11 , the rootstock part  13  has two first plates  31 A, one second plate  31 B, and a second frame  33 . 
     The first plates  31 A and the second plate  31 B are plate-shaped portions, each having a plate surface parallel to a direction I of pressing the second holder  15 , which will be described later. The first plates  31 A and the second plate  31 B are arranged in parallel in a direction intersecting the direction I of pressing the stems of the plants P. The second plate  31 B is interposed between the two first plates  31 A. The two first plates  31 A are each provided with one upward-facing second contact portion  34 A. The second plate  31 B is provided with downward-facing second contact portions  34 B. 
     The second contact portions  34 A,  34 B are identical to the second contact portions  34  of the scion part  2  in  FIG. 4A . Specifically, each of the second contact portions  34 A,  34 B has a pair of second receiving surfaces  35 A,  35 B and a second protrusion  36  provided in a connected portion  35 C of the pair of second receiving surfaces  35 A,  35 B. 
     In the present embodiment, the second protrusion  36  of the upward-facing second contact portion  34 A provided to the first plate  31 A is raised from the upper surface of the first plate  31 A (that is, the plate surface on the scion part  12  side) in a direction toward the tip of the plant P. 
     The second protrusions  36  of the downward-facing second contact portions  34 B are raised from the bottom surface of the second plate  31 B (that is, from the plate surface on the opposite side of the scion part  12  side) in a direction toward the roots of the plant P. 
     The second plate  31 B is displaced relative to the first plates  31 A in a direction parallel to the stems of the plants P. Between the two first plates  31 A and the second plate  31 B, respective slits  33 C,  33 D are formed to guide insertion of the second holder  15 . 
     Similarly to the second frame  33  of the rootstock part  3  in  FIG. 4A , the second frame  33  has two second main magnets  37 A,  37 B that serve as a securing mechanism to detachably secure the scion part  12  to the rootstock part  13 , magnets (not shown) that detachably secure the support part  16 , which will be described later, and two second auxiliary magnets  38 A,  38 B that serve as a securing mechanism to detachably secure the second holder  15  to the rootstock part  13 . 
     As described above, the rootstock part  13  is a mirror image of the scion part  12  with respect to a plane perpendicular to axes of the stems of the plants P (specifically, a horizontal plane). Specifically, the rootstock part  13  is a vertical inversion of the scion part  12  with magnets attached thereto in order to detachably secure the support part  16 . 
     &lt;First Holder&gt; 
     As shown in  FIG. 12A , the first holder  14  is a plate-shaped member configured such that it can be secured to the scion part  12 . The first holder  14  has two upward-facing first press portion  41 A and multiple downward-facing first press portions  41 B that press the stems of the plants P against the respective first contact portions  24 A,  24 B of the scion part  12 , and also has bulging portions  43 . 
     The two upward-facing first press portions  41 A are arranged at both ends in a direction intersecting the direction I of pressing. The downward-facing first press portions  41 B are interposed between the two upward-facing first press portions  41 A. 
     The first press portions  41 A,  41 B are arranged in parallel in a direction intersecting the direction I of pressing the first holder  14 . Each of the first press portions  41 A,  41 B has a pair of first guide surfaces  42 A,  42 B and a cushioning material  42 C. 
     The pair of first guide surfaces  42 A,  42 B, the cushioning materials  42 C, and the bulging portions  43  are identical to the first guide surfaces  42 A,  42 B, the cushioning materials  42 C, and the bulging portions  43  of the first holder  4  in  FIGS. 6A, 6B . 
     In the present embodiment, the bulging portions  43  of the upward-facing first press portions  41 A are raised in a direction toward the tips of the plants P. The upward-facing first press portions  41 A are configured to be stacked from below with the downward-facing first contact portions  24 A provided at both ends of the scion part  12 . 
     The bulging portions  43  of the upward-facing first press portions  41 A come into contact with the receiving surfaces  25 A,  25 B of the downward-facing first contact portions  24 A when the first holder  14  is inserted into the scion part  12 . Moreover, the upper surfaces  42 D (that is, the plate surfaces toward the tips of the plants P) of the upward-facing first press portions  41 A are parallel to the lower surfaces of the first plates  21 A of the scion part  12  and contact the lower surfaces of the first plates  21 A. 
     The bulging portion  43  of the downward-facing first press portion  41 B is raised in a direction toward the roots of the plant P. The downward-facing first press portions  41 B are configured to be stacked from above with the upward-facing first contact portions  24 B of the scion part  12 . 
     The bulging portions  43  of the downward-facing first press portions  41 B come into contact with the receiving surfaces  25 A,  25 B of the upward-facing first contact portions  24 B when the first holder  14  is inserted into the scion part  12 . Moreover, the lower surfaces  42 E (that is, the plate surfaces toward the roots of the plants P) of the downward-facing first press portions  41 B are parallel to the upper surface of the second plate  21 B of the scion part  12  and contact the upper surface of the second plate  21 B. 
     As described above, the first holder  14  has the upward-facing first press portions  41 A and the downward-facing first press portions  41 B with the respective bulging portions  43  protruding in directions different from each other. Accordingly, the first holder  14  is secured to the scion part  12  by the engagement between the upward-facing first press portions  41 A and the downward-facing first contact portions  24 A and the engagement between the downward-facing first press portions  41 B and the upward-facing first contact portions  24 B. 
     The first holder  14  has contact surfaces  46  that guide insertion of the first holder  14  into the scion part  12 . The contact surfaces  46  are each provided between the upward-facing first press portion  41 A and the downward-facing first press portion  41 B. The contact surfaces  46  are parallel to the direction I of pressing the first holder  14  and perpendicular to the upper surfaces  42 D of the upward-facing first press portions  41 A. The contact surfaces  46  contact the inner surfaces of slits  23 C,  23 D of the scion part  12 . 
     Similarly to the first holder  4  in  FIGS. 6A, 6B, and 6C , the first holder  14  also has two magnets  45 A,  45 B that serve as a securing mechanism to detachably secure the first holder  14  to the scion part  12 . 
     &lt;Second Holder&gt; 
     As shown in  FIG. 13 , the second holder  15  is a plate-shaped member configured such that it can be secured to the rootstock part  13 . The second holder  15  has downward-facing second press portions  51 A and upward-facing second press portions  51 B that press the stems of the plants P against the respective second contact portions  34  of the rootstock part  13 , and also has bulging portions  53 . 
     The second press portions  51 A,  51 B are arranged in parallel in a direction intersecting the direction I of pressing the second holder  15 . Each of the second press portions  51 A,  51 B has a pair of second guide surfaces  52 A,  52 B and a cushioning material  52 C. 
     The pair of second guide surfaces  52 A,  52 B, the cushioning materials  52 C, and the bulging portions  53  are identical to the second guide surfaces  52 A,  52 B, the cushioning materials  52 C, and the bulging portions  53  of the second holder  5  in  FIG. 7 . 
     In the present embodiment, the second holder  15  is a mirror image of the first holder  14  with respect to a plane perpendicular to axes of the stems of the plants P (specifically, a horizontal plane). In other words, the second holder  15  is a vertical inversion of the first holder  14 . The second holder  15 , however, may have a portion partly different from the first holder  14 . 
     The second holder  15  is secured to the rootstock part  13  by the engagement between the downward-facing second press portions  51 A and the upward-facing second contact portions  34 A and the engagement between the upward-facing second press portions  51 B and the downward-facing second contact portions  34 B. 
     Similarly to the second holder  5  in  FIG. 7 , the second holder  15  also has two magnets  55 A,  55 B that serve as a securing mechanism to detachably secure the second holder  15  to the rootstock part  13 . 
     &lt;Support Part&gt; 
     As shown in  FIG. 14 , the support part  16  has a body  61 , partitions  64 , and two third main magnets  63 A,  63 B. In the present embodiment, the support part  16  is configured to be detachable from the rootstock part  13 . 
     The body  61  is provided, by the partitions  64 , with internal spaces into which the pods of the plants P can be inserted. The two third main magnets  63 A,  63 B are disposed where the two third main magnets  63 A,  63 B face and abut the rootstock part  13  (specifically, on the upper surface of the body  61 ), and are connected to the respective opposite second main magnets of the rootstock part  13 . 
     [2-2. Effects] 
     The embodiments described hereinabove in detail achieve the following effects. 
     (2a) Due to the rootstock part  13  having a shape that is a mirror image of the scion part  12  with respect to a plane perpendicular to the axes of the stems of the plants P, the same constituent member can be used for both the scion part  12  and the rootstock part  13 . This allows use of the same constituent member for both the first holder  4  and the second holder  5 . As a result, the cost of the grafting member  10  can be reduced. 
     (2b) By having the first holder  14  and the second holder  15  engaged respectively with the first plates and the second plates of the scion part  12  and those of the rootstock part  13 , it is possible to secure the first holder and the second holder without providing securing members for the holders (for example, the first upper plate  22  and the second lower plate  32  in the first embodiment). As a result, the cost of the grafting member  10  can be reduced. 
     3. Third Embodiment 
     [3-1. Configuration] 
     A grafting member  101  shown in  FIG. 15  is a cassette type member for cutting plants and acquiring scions and rootstocks and for joining the acquired scions and rootstocks. 
     The grafting member  101  shown in  FIG. 15  is configured such that the grafting member  101  can be used as the first grafting member so as to acquire the scions and also as the second grafting member so as to acquire the rootstocks. Specifically, the grafting member set of the present embodiment comprises the grafting member  101  as the first grafting member and the grafting member  101  as the second grafting member. 
     The grafting member  101  as the first grafting member and the grafting member  101  as the second grafting member do not have to have exactly the same shape. In other words, the second grafting member may have a part that is shaped differently from the first grafting member. 
     The grafting member  101  comprises a scion part  102 , a rootstock part  103 , a first holder  104 , a second holder  105 , and a support part  106 . Although  FIG. 15  shows an assembled state of these components, each of the components is configured to be detachable. Each component, except cushioning materials which will be described later, may be formed of, for example, resin, metal, or other materials. 
     As shown in  FIG. 16 , the grafting member  101  is configured to be capable of retaining the plants P inside thereof. Although five plants P are retained in  FIG. 16 , the number of the plants P retained in the grafting member  101  is not limited to five. In addition, the type of plants P is not particularly limited. 
     &lt;Scion Part&gt; 
     As shown in  FIG. 17 , the scion part  102  has a first plate  121  and a first frame  123  supporting the first plate  121 . 
     The first plate  121  is a plate-shaped portion having a plate surface parallel to a direction I of pressing (that is, a direction of inserting) the first holder  104 , which will be described later, and perpendicular to the axes of the stems of the plants P. The first plate  121  has first contact portions  124  that come into contact with the respective stems of the plants P at a first position P 1  (see  FIG. 16 ). The first position P 1  is located close to the tips (that is, the stem tips) of the plants P as compared with a cut position of the plants P. 
     The first contact portions  124  and first press portions  141  of the first holder  104  (see  FIG. 20A ) interpose the stems of the plants P therebetween to secure the stems of plants P. The first contact portions  124  are notches provided to the first plate  121 . The first contact portions  124  are arranged in parallel in a direction intersecting the direction I of pressing the first holder  104 . Each first contact portion  124  has a pair of first receiving surfaces  125 A,  125 B, a pair of first gates  125 D,  125 E, and a first protrusion  126  (see  FIG. 17C ). 
     The pair of first receiving surfaces  125 A,  125 B are provided at a position where the pair of first receiving surfaces  125 A,  125 B faces the first press portion  141  of the first holder  104  attached to the scion part  102 , and the distance between the pair of first receiving surfaces  125 A,  125 B decreases along the direction I of pressing the first holder  104 . 
     As shown in  FIG. 17B , the pair of first receiving surfaces  125 A,  125 B have a shape of a curved line that is bent smoothly when viewed from a direction parallel to the axis of the stem of the plant P (hereinafter also referred to as a “plant P axis direction”). The edges of the pair of first receiving surfaces  125 A,  125 B in the plant P axis direction are chamfered. The axes of the stems of the plants P are, for example, parallel to the vertical direction. 
     The pair of first gates  125 D,  125 E is arranged at the opening of a notch that forms the first contact portion  124  (that is, outside the corresponding pair of first receiving surfaces  125 A,  125 B). The pair of first gates  125 D,  125 E protrudes in directions opposing to each other. The first gates  125 D,  125 E inhibit the plant P placed in the first contact portion  124  from moving out of the first contact portion  124  before the first holder  104  is secured. 
     The first contact portion  124  does not have to have the pair of first gates  125 D,  125 E. In other words, the first receiving surfaces  125 A,  125 B may reach the end face of the first plate  121 . 
     As shown in  FIG. 17C , the first protrusion  126  is provided in a connected portion  125 C of the pair of first receiving surfaces  125 A,  125 B (that is, in the innermost part of the first contact portion  124 ), and the first protrusion  126  protrudes in the plant P axis direction beyond the first receiving surfaces  125 A,  125 B. Specifically, the first protrusion  126  protrudes from the bottom surface of the first plate  121  in a direction toward the roots of the plant P. The leading end of the first protrusion  126  is curved like an arc. 
     As shown in  FIG. 17B , the first protrusion  126  has a curved surface depressed in an arc-shape in the direction I of pressing when viewed in the plant P axis direction. The stem of the plant P placed in the first contact portion  124  is pressed against the curved surface. 
     As shown in  FIG. 17A , the scion part  102  has two slits  129 A,  129 B and two grooves  129 C,  129 D to secure the first holder  104 . The slits  129 A,  129 B are each provided between the first plate  121  and the first frame  123  and extend in parallel to the direction I of pressing. The grooves  129 C,  129 D are each formed by a part of the first plate  121  being depressed in the thickness direction and extend in parallel to the direction I of pressing. 
     As shown in  17 B, the first frame  123  has a pin  127 A and a hole  127 B that serve as a securing mechanism to detachably secure the scion part  102  and the rootstock part  103 . The pin  127 A and the hole  127 B are arranged where the pin  127 A and the hole  127 B face and abut the rootstock part  103  (specifically, on the bottom surface of the first frame  123 ), and respectively mate with a hole  137 B and a pin  137 A of the rootstock part  103 . 
     The scion part  102  of the grafting member  101  as the first grafting member is configured to be attachable, while the first holder  104  is secured thereto, to the rootstock part  103  of the grafting member  101  as the second grafting member to which the second holder  105  is secured. 
     &lt;Rootstock Part&gt; 
     As shown in  FIG. 18 , the rootstock part  103  has a second plate  131  and a second frame  133  supporting the second plate  131 . 
     The second plate  131  is a plate-shaped portion having a plate surface parallel to a direction I of pressing the second holder  105 , which will be described later, and perpendicular to the axes of the stems of the plants P. The second plate  131  has second contact portions  134  that come into contact with the respective stems of the plants P at a second position P 2  (see  FIG. 16 ). The second position P 2  is located close to the roots of the plants P as compared with the cut position of the plants P. 
     The second contact portions  134  and second press portions  151  of the second holder  105  (see  FIG. 22 ) interpose the stems of the plants P therebetween to secure the stems of plants P. The second contact portions  134  are arranged in parallel in a direction intersecting the direction I of pressing the second holder  105 . Each second contact portion  134  has a pair of second receiving surfaces  135 A,  135 B, two second gates  135 D,  135 E, and a second protrusion  136 . Each second contact portion  134  is arranged at a position to be aligned with the corresponding first contact portion  124  while the scion part  102  and the rootstock part  103  are secured. 
     In the present embodiment, the rootstock part  103  is a mirror image of the scion part  102  with respect to a plane perpendicular to axes of the stems of the plants P (specifically, a horizontal plane). In other words, the rootstock part  103  includes the constituent members of the scion part  102  arranged in a vertically inverted manner. The second contact portions  134  and the first contact portions  124 , thus, have the same shape. The rootstock part  103 , however, may have a portion partly different from the scion part  102 . 
     The pair of second receiving surfaces  135 A,  135 B is provided at a position where the pair of second receiving surfaces  135 A,  135 B faces the second press portion  151  of the second holder  105  attached to the rootstock part  103 , and the distance between the pair of second receiving surface  135 A,  135 B decreases along the direction I of pressing the second holder  105 . The pair of second gates  135 D,  135 E is provided at the opening of a notch that forms the second contact portion  134 . 
     The second receiving surfaces  135 A,  135 B and the second gates  135 D,  135 E respectively have the same shapes as those of the first receiving surfaces  125 A,  125 B and the first gates  125 D,  125 E of the scion part  102 . Accordingly, detailed description of these components will be omitted. The second contact portions  134  do not have to have the pair of second gates  135 D,  135 E. 
     The second protrusion  136  is provided in a connected portion  135 C of the pair of second receiving surfaces  135 A,  135 B (that is, in the innermost part of the second contact portion  134 ), and the second protrusion  136  protrudes in the plant P axis direction beyond the second receiving surfaces  135 A,  135 B. Specifically, the second protrusion  136  protrudes from the upper surface of the second plate  131  in a direction toward the tip of the plant P. The leading end of the second protrusion  136  is curved like an arc. 
     The rootstock part  103  has two slits  139 A,  139 B, two grooves  139 C,  139 D, a pin  137 A, a hole  137 B, and two lower holes  138 A,  138 B. The slits  139 A,  139 B, the grooves  139 C,  139 D, the pin  137 A, and the hole  137 B respectively have the same shapes as those of the slits  129 A,  129 B, the grooves  129 C,  129 D, the pin  127 A, and the hole  127 B of the scion part  102 . 
     The two lower holes  138 A,  138 B form a securing mechanism that secures the support part  106  to the rootstock part  103 . The two lower holes  138 A,  138 B are arranged where the two lower holes  138 A,  138 B face and abut the support part  106  (that is, on the lower surface of the second frame  133 ), and respectively mate with the two pins  163 A,  163 B (see  FIG. 23 ) of the support part  106 . 
     &lt;First Holder&gt; 
     As shown in  FIG. 19 , the first holder  104  is configured such that the first holder  104  can be secured to the scion part  102 . In the present embodiment, the first holder  104  is inserted in the horizontal direction to be aligned with the first plate  121  of the scion part  102 . Accordingly, the first holder  104  is secured to the scion part  102 . 
     As shown in  FIG. 20A , the first holder  104  has first press portions  141  that press the respective stems of the plants P against the first contact portions  124  of the scion part  102 . The first press portions  141  are arranged at positions where the first press portions  141  face the first contact portions  124  in the direction I of pressing the first holder  104 . 
     The first press portions  141  are arranged in parallel in a direction intersecting the direction I of pressing the first holder  104 . Each of the first press portions  141  has a pair of first guide surfaces  142 A,  142 B and a first cushioning material  142 C. 
     The first cushioning material  142 C is a plate-shaped member that presses the stem of the plant P against the corresponding first contact portion  124 . The first cushioning material  142 C is made of a material that can be deformed to a certain extent by contact of the stem of the plant P. 
     Examples of the material forming the first cushioning material  142 C include porous materials such as sponges. Elastic materials, such as rubber, may be also used for the material forming the first cushioning material  142 C. In  FIG. 20A  and other drawings, the first cushioning material  142 C has a square planar shape; the planar shape of the first cushioning material  142 C, however, may be, for example, triangular, circular, or any other shape. 
     As shown in  FIG. 20B , the pair of first guide surfaces  142 A,  142 B is, in a planar view, spaced apart from each other and protrudes in the direction I of pressing the first holder  104  beyond the first cushioning material  142 C. The pair of first guide surfaces  142 A,  142 B is provided at a position where the pair of first guide surfaces  142 A,  142 B faces the first contact portion  124  of the scion part  2 , and the distance between the pair of first guide surfaces  142 A,  142 B increases along the direction I of pressing the first holder  104 . 
     Specifically, the first cushioning materials  142 C are fixed to supports  147  that protrude in the direction I of pressing from a frame  145 , extending in a direction perpendicular to the direction I of pressing, by, for example, an adhesive. As shown in  FIG. 20C , the supports  147  have plate-shaped extended portions  146  overlapping the first cushioning materials  142 C in the thickness direction. The supports  147  are stacked with the first plate  121  of the scion part  102  in the thickness direction while the first holder  104  is secured to the scion part  102 . The extended portions  146  slide on the plate surface of the first plate  121  when the first holder  104  is inserted. In the present embodiment, the first cushioning materials  142 C are fixed to the surfaces of the extended portions  146 ; the first cushioning materials  142 C, however, may be fixed to surfaces of other portions apart from the extended portions  146  of the supports  147 . 
     The pair of first guide surfaces  142 A,  142 B is formed by the end faces of the extended portions  146 . The first cushioning materials  142 C are disposed to overlap a part of the pair of first guide surfaces  142 A,  142 B in the plant P axis direction (that is, in the thickness direction the first cushioning materials  142 C). 
     As shown in  FIG. 20A , the pair of first guide surfaces  142 A,  142 B has a shape of a curved line that is bent smoothly when viewed from the plant P axis direction. The edges of the pair of first guide surfaces  142 A,  142 B in the plant P axis direction are chamfered. 
     The end of the first cushioning material  142 C, together with a part of the pair of first guide surfaces  142 A,  142 B, forms a C-shaped recess when viewed in the thickness direction of the first cushioning material  142 C. The stem of the plant P placed in the first contact portion  124  is brought into contact with the first cushioning material  142 C of the first press portion  141  and the first protrusion  126  of the first contact portion  124 . The stem of the plant P is retained between the first contact portion  124  and the first press portion  141 , thus being inhibited from moving in the direction of the diameter of the stem. 
     The extended portions  146  do not have to be plate-shaped, and may have a shape with a thickness that is equivalent to the thickness of the frame  145  as shown in  FIG. 21A  or  FIG. 21B . In the configuration shown in  FIG. 21A  or  FIG. 21B , the first cushioning material  142 C (not shown in  FIG. 21A  and  FIG. 21B ) is placed on a mount  148  disposed between the pair of first guide surfaces  142 A,  142 B, and is fixed to the upper surface of the mount  148  or the lateral surfaces  146 A of the extended portion  146 . 
     As shown in  FIG. 20A , the first holder  104  has two snaps  144 A,  144 B, two blocks  144 C,  144 D, and two tabs  144 E,  144 F. The two snaps  144 A,  144 B protrude from the frame  145  in the direction I of pressing, and are provided at positions where the two snaps  144 A,  144 B interpose the first press portions  141  therebetween. The two blocks  144 C,  144 D and the two tabs  144 E,  144 F protrude from the frame  145  in the direction I of pressing, and are each disposed between the first press portions  141 . 
     The snaps  144 A,  144 B are a securing mechanism to detachably secure the first holder  104  to the scion part  102 , and is inserted into the slits  129 A,  129 B of the scion part  102 . The snaps  144 A,  144 B have hook-shaped ends that are engageable with protrusions provided in the slits  129 A,  129 B. 
     The blocks  144 C,  144 D and the tabs  144 E,  144 F are a guide mechanism to guide insertion of the first holder  104  along the direction I of pressing. The blocks  144 C,  144 D are inserted into the grooves  129 C,  129 D of the scion part  102 . The tabs  144 E,  144 F overlap the plate surface of the first plate  121  of the scion part  102 . 
     &lt;Second Holder&gt; 
     As shown in  FIG. 19 , the second holder  105  is configured such that the second holder  105  can be secured to the rootstock part  103 . In the present embodiment, the second holder  105  is inserted to overlap the second plate  131  of the rootstock part  103  in the horizontal direction. Accordingly, the second holder  105  is secured to the rootstock part  103 . 
     As shown in  FIG. 22 , the second holder  105  has second press portions  151  that press the respective stems of the plants P against the second contact portions  134  of the rootstock part  103 . The second press portions  151  are arranged at positions where the second press portions  151  face the second contact portions  134  in a direction I of pressing the second holder  105 . 
     The second press portions  151  are arranged in parallel in a direction intersecting the direction I of pressing the second holder  105 . Each of the second press portions  151  has a pair of second guide surfaces  152 A,  152 B and a second cushioning material  152 C. 
     In the present embodiment, the second holder  105  is a mirror image of the first holder  104  with respect to a plane perpendicular to axes of the stems of the plants P (specifically, a horizontal plane). In other words, the second holder  105  is a vertical inversion of the first holder  104 . The second holder  105 , however, may have a portion partly different from the first holder  104 . 
     The second cushioning material  152 C is a plate-shaped member that presses the stem of the plant P against the corresponding second contact portion  134 . The pair of second guide surfaces  152 A,  152 B is, in a planar view, spaced apart from each other and protrudes in the direction I of pressing the second holder  105  beyond the second cushioning material  152 C. The pair of second guide surfaces  152 A,  152 B is arranged at a position where the pair of second guide surfaces  152 A,  152 B faces the second contact portion  134  of the rootstock part  103 , and the distance between the pair of second guide surfaces  152 A,  152 B increases along the direction I of pressing the second holder  105 . 
     The second guide surfaces  152 A,  152 B and the second cushioning material  152 C have the same shapes as those of the first guide surfaces  142 A,  142 B and the first cushioning material  142 C of the first press portion  141  of the first holder  104 . Accordingly, detailed description of these components will be omitted. 
     The second holder  105  has two snaps  154 A,  154 B each protruding from a frame  155 , two blocks  154 C,  154 D, and two tabs  154 E,  154 F. The snaps  154 A,  154 B, the blocks  154 C,  154 D, and the tabs  154 E,  154 F respectively have the same shapes as those of the snaps  144 A,  144 B, the blocks  144 C,  144 D, and the tabs  144 E,  144 F of the first holder  104 . 
     The two snaps  154 A,  154 B are inserted into the slits  139 A,  139 B of the rootstock part  103 . The two blocks  154 C,  154 D are inserted into the grooves  139 C,  139 D of the rootstock part  103 . 
     As shown in  FIG. 15 , a space S is provided between the first holder  104  secured to the scion part  102  and the second holder  105  secured to the rootstock part  103  to expose the stems of the plants P. The stems are cut in the space S to acquire scions and rootstocks of the plants P. 
     &lt;Support Part&gt; 
     As shown in  FIG. 16 , the support part  106  supports pods Q in which the roots of the plants P are contained. 
     As shown in  FIG. 23 , the support part  106  has a body  161 , partitions  164 , and two pins  163 A,  163 B. In the present embodiment, the support part  106  is configured to be detachable from the rootstock part  103 . 
     The body  161  is provided, by the partitions  164 , with internal spaces into which the pods of the plants P can be inserted. The two pins  163 A,  163 B are disposed where the two pins  163 A,  163 B face and abut the rootstock part  103  (specifically, the upper surface of the body  161 ), and respectively mate with lower holes  138 A,  138 B of the rootstock part  103 . 
     [3-2. Effects] 
     The embodiments described hereinabove in detail achieve the following effects. 
     (3a) The first contact portions  124  and the first press portions  141 , and the second contact portions  134  and the second press portions  151  enable securing of the stems of the plants P respectively in the scion part  102  and the rootstock part  103  at two positions, namely at the upper position and the lower position, in the vicinity of cut sections. Accordingly, the positional accuracy of the stems to be joined is improved. Moreover, the first cushioning materials  142 C and the second cushioning materials  152 C can inhibit displacement of the stems. As a result, grafting accuracy is improved. 
     (3b) The pairs of first guide surfaces  142 A,  142 B protrude beyond the first cushioning materials  142 C, and the pairs of second guide surfaces  152 A,  152 B protrude beyond the second cushioning material  152 C. This configuration facilitates to guide the stems of the plants P easily and accurately to the first cushioning materials  142 C and the second cushioning materials  152 C. 
     (3c) The disposition of the first cushioning material  142 C and the second cushioning material  152 C to respectively overlap the pair of first guide surfaces  142 A,  142 B and the pair of second guide surfaces  152 A,  152 B in the plant P axis direction facilitates positioning of the first cushioning materials  142 C and the second cushioning materials  152 C respectively on the first holder  104  and the second holder  105 . As a result, the first cushioning materials  142 C and the second cushioning materials  152 C can be easily replaced. 
     (3d) Due to the securing mechanisms made up of the pin  127 A and the hole  127 B of the scion part  102  and the pin  137 A and the hole  137 B of the rootstock part  103 , rootstocks and scions after joining can be pressed each other. As a result, it is possible to inhibit separation between the rootstocks and the scions during healing or during transportation. 
     4. Fourth Embodiment 
     [4-1. Configuration] 
     A grafting member  201  shown in  FIG. 24  is a cassette type member for cutting plants and acquiring scions and rootstocks and for joining the acquired scions and rootstocks. 
     The grafting member  201  shown in  FIG. 24  is configured such that the grafting member  201  can be used as the first grafting member to acquire scions and also as the second grafting member to acquire rootstocks. Specifically, a grafting member set of the present embodiment comprises the grafting member  201  as the first grafting member and the grafting member  201  as the second grafting member. 
     The grafting member  201  comprises a scion part  202 , a rootstock part  203 , a first holder  204 , a second holder  205 , and a support part  206 . The grafting member  201  is a rearrangement of the scion part  102 , the rootstock part  103 , the first holder  104 , and the second holder  105  of the grafting member  101  in  FIG. 15 . The support part  206  of the grafting member  201  is similar to the support part  106  of the grafting member  101  in  FIG. 15 ; the description of which, thus, will be omitted. 
     &lt;Scion Part&gt; 
     As shown in  FIG. 25A , the scion part  202  has a first plate  221  and a first frame  123  supporting the first plate  221 . Out of the components of the scion part  202 , those that are identical to the components of the scion part  102  in FIG.  15  will be hereinafter assigned with the same reference numerals, and description of such components will be omitted. 
     Similarly to the grafting member  101  in  FIG. 15 , the first plate  221  has first contact portions  224  that come into respective stems of the plants P. The first contact portions  224  are similar to the first contact portions  124  of the grafting member  101  in  FIG. 15  except that the shape of the first contact portions  224  in planar view is different. 
     Each first contact portion  224  has a pair of first receiving surfaces  225 A,  225 B and a first protrusion  126  (see  FIG. 25C ). The pair of first receiving surfaces  225 A,  225 B is provided at a position where the pair of first receiving surfaces  225 A,  225 B faces the first press portion  241  of the first holder  204  attached to the scion part  202 , and the distance between the pair of first receiving surfaces  225 A,  225 B decreases along a direction I of pressing the first holder  204 . 
     As shown in  FIG. 25B , the pair of first receiving surfaces  125 A,  125 B each have a curve  225 D that is bent smoothly when viewed from the plant P axis direction, and a planar portion  225 E formed by a planar surface parallel to the plant P axis direction. 
     The planar portion  225 E is provided continuously to a connected portion  125 C of the pair of first receiving surfaces  125 A,  125 B (that is, the first protrusion  126 ). The planar portion  225 E is arranged on the inner side of the curves  225 D, that is, between the curve  225 D and the first protrusion  126 . 
     &lt;Rootstock Part&gt; 
     The rootstock part  203  is a mirror image of the scion part  202  with respect to a plane perpendicular to axes of the stems of the plants P (specifically, a horizontal plane). In other words, the rootstock part  203  includes the constituent members of the scion part  202  arranged in a vertically inverted manner. 
     Accordingly, the rootstock part  203  is configured such that the second contact portions  134  in the rootstock part  103  shown in  FIG. 15  are identically shaped to the first contact portions  224  of the scion part  202 . The rootstock part  203 , however, may have a portion partly different from the scion part  202 . 
     &lt;First Holder&gt; 
     The first holder  204  is configured such that the first holder  204  can be secured to the scion part  202 . As shown in  FIGS. 26A, 26B , the first holder  204  has first press portions  241  that press the respective stems of the plants P against the first contact portions  224  of the scion part  202 , and a first cushioning material structure  243  disposed across the first press portions  241 . Out of the components of the first holder  204 , those that are identical to the components of the first holder  104  in  FIG. 15  will be hereinafter assigned with the same reference numerals, and description of such components will be omitted. 
     The first press portions  241  are arranged at positions where the first press portions  241  face the first contact portions  224  in the direction I of pressing the first holder  204 . Each of the first press portions  241  has a pair of first guide surfaces  242 A,  242 B and a first cushioning material  242 C. 
     The first guide surfaces  242 A,  242 B and the first cushioning material  242 C have the same functions as those of the first guide surfaces  142 A,  142 B and the first cushioning material  142 C in the first press portion  141  of the first holder  104  in  FIG. 15 . 
     The first cushioning materials  242 C of the first press portions  241  are each a part of the first cushioning material structure  243 . Specifically, as shown in  FIGS. 26B and 26C , the portions of the first cushioning material structure  243  that are exposed between walls  247  constitute the respective first cushioning materials  242 C. 
     The material of the first cushioning material structure  243  is the same as that of the first cushioning materials  142 C in the first holder  104  in  FIG. 15 . The first cushioning material structure  243  is rod-shaped and arranged so that the longitudinal direction of the rod shape intersects the direction I of pressing the first holder  204 . 
     Specifically, the first cushioning material structure  243  is disposed in a groove provided between the frame  145  and the walls  247  that are spaced apart from the frame  145  in the direction I of pressing. The walls  247  extend in a direction intersecting the direction I of pressing, and the ends of the walls  247  in the extending direction constitute the first guide surfaces  142 A,  142 B. 
     The first cushioning material structure  243  is fixed to the frame  145 , walls  247 , or an extended portion  246  extending from the frame  145  by, for example, an adhesive. The extended portion  246  couples the frame  145  and the walls  247 , and forms the bottom surface of the groove in which the first cushioning material structure  243  is disposed. 
     &lt;Second Holder&gt; 
     The second holder  205  is configured such that the second holder  205  can be secured to the rootstock part  203 . The second holder  205  is a mirror image of the first holder  204  with respect to a plane perpendicular to axes of the stems of the plants P (specifically, a horizontal plane). In other words, the second holder  205  is a vertical inversion of the first holder  204 . 
     Accordingly, the second holder  205  is achieved by placing a second cushioning material structure on the second holder  105  in  FIG. 15  across the second press portions  151 . The second holder  205 , however, may have a portion partly different from the first holder  204 . 
     [4-2. Effects] 
     The embodiments described hereinabove in detail achieve the following effects. 
     (4a) By making the cushioning materials of the first holder  204  and the cushioning materials of second holder  205  into respective single cushioning material structures, it is possible to reduce the number of parts disposed in the holders. As a result, attachment and replacement of cushioning materials can be facilitated. 
     (4b) With the planar portions of the receiving surfaces of the scion part  202  and the receiving surfaces of the rootstock part  203 , it is possible to accurately guide the stems of plants to specified positions by the first holder  204  and the second holder  205 , while biting by the stems are inhibited. 
     5. Fifth Embodiment 
     [5-1. Configuration] 
     A method for producing grafted seedlings shown in  FIG. 27  is to produce seedlings by grafting scions and rootstocks with the grafting member  1  in  FIG. 1 , the grafting member  10  in  FIG. 9 , the grafting member  101  in  FIG. 15 , or the grafting member  201  in  FIG. 24 . Hereinbelow, the grafting member  1  in  FIG. 1  will be used to describe each step. 
     The method for producing grafted seedlings in the present embodiment comprises a preparation step S 10 , a first contact step S 20 , a first securing step S 30 , a first cutting step S 40 , a second contact step S 50 , a second securing step S 60 , a second cutting step S 70 , a joining step S 80 , and a healing step S 90 . 
     &lt;Preparation Step&gt; 
     In the present step, the grafting member  1  as the first grafting member and the grafting member  1  as the second grafting member are prepared. 
     &lt;First Contact Step&gt; 
     In the present step, the rootstock part  3  is attached to the scion part  2 ; stems of first plants, which supply scions, are brought into contact with the first contact portions  24  of the scion part  2  in the first grafting member while the first holder  4  and the second holder  5  are unattached; and the stems of the first plants are thus brought into contact with the second contact portions  34  of the rootstock part  3  in the first grafting member. 
     In the above-described operation, pods of the first plants are inserted into the support part  6  attached to the rootstock part  3 . The rootstock part  3  may be attached to the support part  6  upon insertion of the pods of the first plants into the support part  6 . 
     &lt;First Securing Step&gt; 
     In the present step, the first holder  4  and the second holder  5  are secured to the scion part  2  and the rootstock part  3  in the first grafting member so that the stems of the first plants are secured between the first contact portions  24  and the first press portions  41  and between the second contact portions  34  and the second press portions  51 . The first holder  4  and the second holder  5  may be secured in any order. 
     &lt;First Cutting Step&gt; 
     In the present step, the stems of the first plants are concurrently cut in the space S between the first holder  4  and the second holder  5  in the first grafting member (that is, at a position close to roots of the first plants as compared with the first holder  4 ). 
     &lt;Second Contact Step&gt; 
     The present step is the same as the first contact step S 20  except that the second grafting member is used in place of the first grafting member, and the second plants that supply rootstocks are used in place of the first plants. 
     &lt;Second Securing Step&gt; 
     The present step is the same as the first securing step S 30  except that the second grafting member and the second plants are used. 
     &lt;Second Cutting Step&gt; 
     The present step is the same as the first cutting step S 40  except that the second grafting member and the second plants are used and the stems of the second plants are cut in the space S between the first holder  4  and the second holder  5  (that is, at a position away from roots of the second plants as compared with the second holder  5 ). However, it is desirable in light of joining properties that the second plants are cut at a position close to the tips of the plants as compared with the cut position of the first plants. 
     &lt;Joining Step&gt; 
     In the present step, cut surfaces of the stems of the first plants secured by the scion part  2  of the first grafting member and cut surfaces of the stems of the second plants secured by the rootstock part  3  of the second grafting member are concurrently joined. 
     &lt;Healing Step&gt; 
     In the present step, plants achieved by joining scions derived from the first plants and rootstocks derived from the second plants undergo healing. The healing is performed, for example, in a light place under weak light. 
     The secured states of the first holder  4  of the first grafting member and the second holder  5  of the second grafting member respectively to the scion part  2  and the rootstock part  3  are maintained until the healing step S 90 . 
     [5-2. Effects] 
     The embodiments described hereinabove in detail achieve the following effects. 
     ( 5 a) Use of the grafting member  1  can improve grafting accuracy. 
     Productivity of grafted seedlings can be also improved since the already-grown first plant and second plant are used. Furthermore, grafting can be performed irrespective of the size of plants. Moreover, since one type of the grafting member  1  can be used for both scions and rootstocks, the equipment cost can be reduced. 
     6. Sixth Embodiment 
     [6-1. Configuration] 
     A grafting member set  300  shown in  FIG. 28  comprises a first grafting member  301 A and a second grafting member  301 B. In the grafting member set  300 , the first grafting member  301 A and the second grafting member  301 B have different shapes. 
     The first grafting member  301 A corresponds to the grafting member  1  in  FIG. 1  from which the second upper plate  31 , the second lower plate  32 , and the second contact portions  34  (that is, portions other than the second frame  33 ) of the rootstock part  3 , and the second holder  5  are removed. The scion part  2 , the second frame  33 , the first holder  4 , and the support part  6  of the first grafting member  301 A are identical to those of the grafting member  1  in  FIG. 1 . In the first grafting member  301 A, plants are cut in a space between the first holder  4  and the second frame  33 . 
     The second grafting member  301 B corresponds to the grafting member  1  in  FIG. 1  from which the scion part  2  and the first holder  4  are removed. The rootstock part  3 , the second holder  5 , and the support part  6  of the second grafting member  301 B are identical to those of the grafting member  1  in  FIG. 1 . In the second grafting member  301 B, plants are cut at a position along the upper surface of the rootstock part  3 . 
     As shown in  FIG. 29 , the second frame  33  of the first grafting member  301 A has depressions (steps)  33 E,  33 F, having a height smaller than the remainder portion of the second frame  33 , on the upper surface (that is, the surface facing the scion part  2 ) of the second frame  33  at the end from which the first holder  4  is inserted. In other words, in the first grafting member  301 A, plants are cut on the lower side of the cut position (that is, the upper surface of the rootstock part  3 ) in the second grafting member  301 B. 
     [6-2. Effects] 
     The embodiments described hereinabove in detail achieve the following effects. 
     (6a) In the first grafting member  301 A, the recesses  33 E,  33 F allow cutting of plants at a position closer to the roots of the plants than in the second grafting member  301 B. Accordingly, the cut position of rootstocks is located close to the tips of the plants as compared with the cut position of scions, and overlapping portions are created in the axis direction of the plants. This improves joining properties of rootstocks and scions. 
     ( 6 b) Since the first grafting member  301 A and the second grafting member  301 B have minimum configurations respectively required for acquiring scions and rootstocks, the number of parts is reduced as compared with the grafting member  1  in  FIG. 1 . As a result, the cost of each grafting member can be reduced. 
     7. Other Embodiments 
     Embodiments of the present disclosure are described hereinabove; it goes without saying, however, that the present disclosure can be implemented in various modes without being limited to the above-described embodiments. 
     (7a) In the grafting members of the above-described embodiments, the width of the first protrusions and the width of the second protrusions do not have to be decreased with an increase in distance respectively from the pair of first receiving surfaces and the pair of second receiving surfaces. Moreover, the first contact portions and the second contact portions do not have to have the first protrusions and the second protrusions, respectively. 
     (7b) In grafting members of the above-described embodiments, each pair of first receiving surfaces, the pair of first guide surfaces, the pair of second receiving surfaces, and the pair the second guide surfaces does not have to have the shape of a curved line that is bent when viewed from the axis direction of plants. In other words, these surfaces may have the shape of straight lines (that is, flat surfaces) when viewed from the axis direction of plants. 
     (7c) In the grafting members in the above-described embodiments, the first press portions and the second press portions do not have to have the respective cushioning materials. Moreover, the first press portions and the second press portions do not have to have the pairs of first guide surfaces and the pairs of second guide surfaces, respectively. 
     (7d) In the grafting members in the above-described embodiments, the direction of pressing the first holder and the direction of pressing the second holder are not limited to the horizontal direction. Moreover, the first holder and the second holder do not have to be inserted into the scion part and the rootstock part, respectively. For example, the first holder and the second holder may be secured by other members while being respectively pressed against the scion part and the rootstock part. 
     (7e) In the grafting member in the above-described embodiments, other mechanisms apart from the magnets, the combination of the protrusions and the holes, and the snap mechanism, which have been described in the aforementioned embodiments, may be used for the securing mechanism that secures the scion part to the rootstock part, the securing mechanism that secures the first holder to the scion part, and the securing mechanism that secures the second holder to the rootstock part. Furthermore, the grafting member does not necessarily have to comprise these securing mechanisms. 
     (7f) In the grafting member in the above-described embodiments, the support part may be undetectably fixed to (that is, integrated with) the rootstock part. Moreover, the grafting member does not necessarily have to comprise the support part. 
     (7g) In the method for producing grafted seedling in the above-described embodiment, the grafting member  1  in  FIG. 1  may be substituted with the first grafting member  301 A and the second grafting member  301 B of the grafting member set  300  in  FIG. 28 . In this case, the stems of the first plants do not have to be brought into contact with the second contact portions  34  in the first contact step, and the stems of the second plants do not have to be brought into contact with the first contact portions  24  in the second contact step. Moreover, the second holder  5  does not have to be secured in the first securing step, and the first holder  4  does not have to be secured in the second securing step. 
     (7h) The grafting member in the above-described embodiments may be configured to be capable of retaining one piece of plant. Moreover, each step may be performed for one piece of the first plant and one piece of the second plant in the method for producing grafted seedling in the above-described embodiment. 
     (7i) The grafting member in the above-described embodiments may further comprise an additional rootstock part that is detachable from the rootstock part and has at least one third contact portion that comes into contact with a stem of a plant at a third position that is close to the roots of the plant as compared with the second position. The grafting member may further comprise a third holder that can be secured to the additional rootstock part and has at least one third press portion that presses the stem of the plant against at least one third contact portion. Between the third holder and the second holder, a space is provided to expose the stem of the plant. 
     The additional rootstock part has a configuration similar to that of the scion part or the rootstock part. The third holder has a configuration similar to that of the first holder or the second holder. The support part that supports the pods may be attached to the additional rootstock part. 
     The drafting member comprising the additional rootstock part and the third holder (hereinafter also referred to as an “intermediate rootstock grafting member”) is used for grafting three or more types of different plants by grafting a scion, an intermediate rootstock, and a rootstock. The intermediate rootstock consists of a stem of a plant from which the roots and the stem tip are cut off. In the intermediate rootstock grafting member, the plans retained therein are cut at two points, namely at an upper point and a lower point, to make the scion, the intermediate rootstock, and the rootstock. In other words, the intermediate rootstock is retained in the rootstock part, and the rootstock is retained in the additional rootstock part. 
     The scion part retaining the scion, the rootstock part retaining the intermediate rootstock, and the additional rootstock part retaining the rootstock are each joined with a scion part, a rootstock part, and an additional rootstock part retaining a scion, an intermediate rootstock, or a rootstock of other plants so as to perform grafting. 
     The intermediate rootstock grafting member may have two or more additional rootstock parts. In other words, the intermediate rootstock grafting member can be also used for grafting two or more intermediate rootstocks. In this case, a rootstock is retained in the additional rootstock part that is located farthest from the scion part. 
     (7j) For example, a function of one constituent element in the above-described embodiments may be divided as multiple constituent elements, and/or functions of multiple constituent elements may be consolidated and assigned to a single constituent element. Also, the configurations of the above-described embodiments may be partly omitted. Further, at least a part of a configuration in the above-described embodiments may be added to, or may replace, another configuration of the above-described embodiments. Any form that falls within the scope of the technical ideas defined in the language of the appended claims may be an embodiment of the present disclosure. 
     8. Examples 
     The following describes details of tests conducted to confirm the effects of the present disclosure, and evaluation of the effects. 
     Example 1 
     Seeds for rootstock tomatoes and seeds for scion tomatoes were sown in respective trays with soil for a gardening use, covered with vermiculite for a gardening use, and then left the seeds for water absorption and germination. 
     A grafting operation was performed on the seedlings raised for one to two weeks after the seeding using the grafting member  1  in  FIG. 1 . Specifically, the rootstock plants and the scion plants were removed from the trays and secured in the grafting member. 
     After securing each plant, the stem of each plant was cut with a razor, and the rootstock part and the scion part were separated. After separation of the units, the scion part, where the plants for scions were secured, was secured to the rootstock part where the plants for rootstocks were secured. Subsequently, the plants were healed under high-humidity conditions for three to five days for rooting of the stems of the rootstock plants and the scion plants. 
     Example 2 
     Grafting was performed under the same conditions as in Example 1 except that the grafting member  101  in  FIG. 15  was used as the grafting member. 
     Example 3 
     Grafting was performed under the same conditions as in Example 1 except that the grafting member  201  in  FIG. 24  was used as the grafting member. 
     Comparative Example 
     Grafting was performed under the same conditions as in Example 1 except that the seedling nursery member disclosed in International Patent Publication No. 2016/129683 was used as the grafting member. 
     Evaluation 
     The rates of stem damages caused when the stems of the plants were secured in the grafting members were evaluated in Examples 1 to 3 and in Comparative Example. The damage rates were obtained by the ratios of the number of plants with damaged stems relative to the total number of plants used in the respective tests in Examples 1 to 3 and Comparative Example, and the examples were graded A, B, and C from an example with a smaller damage rate. 
     The rooting rates of the plants were also evaluated in Examples 1 to 3 and 
     Comparative Example. The rooting rates were obtained by the ratios of the number of plants that had developed roots relative to the total number of plants used in the respective tests in Examples 1 to 3 and Comparative Example, and the examples were graded A, B, and C from an example with a higher rooting rate. Plants were determined to have developed roots if the scions did not separate from the rootstocks when being removed from the grafting member after the three to five days of healing. 
     The above-described damage rates and the rooting rates are shown in Table 1. As shown in Table 1, all Embodiments 1 to 3 had better rooting rates than Comparative Example. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Damage Rate 
                 Rooting Rate 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                   
                 Comparative Example 
                 A 
                 C 
               
               
                   
                 Example 1 
                 A 
                 B 
               
               
                   
                 Example 2 
                 B 
                 A 
               
               
                   
                 Example 3 
                 A 
                 A