bluuebunny/crossref_metadata_2025 huggingface dataset:
GENOME RELATIONS AMONG ELYMUS CANADENSIS, ELYMUS TRITICOIDES, ELYMUS DASYSTACHYS, AND AGROPYRON SMITHII
Authors: Dewey Douglas R.
Published: January 2018

Hand‐emasculated Elymus canadensis pollinated by E. triticoides, E. dasystachys, and Agropyron smithii yielded 15, 21, and 1 viable hybrid seeds from 56, 52, and 52 florets, respectively. The 28‐chromosome species—E. canadensis, E. triticoides, and E. dasystachys—behaved meiotically as allotetraploids and consistently formed 14 bivalents at metaphase I. Octoploid A. smithii, 2n = 56, averaged 0.41I, 27.72II, and 0.03IV in 87 metaphase‐I cells. Agropyron smithii is apparently an allooctoploid or a segmental autoallooctoploid. Meiosis was similar in the E. canadensis X E. triticoides and E. dasystachys hybrids. Chromosome pairing was very low in both hybrids, about two loosely connected open‐ended bivalents per cell, and may not represent genuine homologies. The genomes of E. canadensis are distinctly different from those of E. triticoides and E. dasystachys. The E. canadensis X A. smithii hybrid averaged 13.37I and 14.31II in 76 metaphase‐I cells. More than half of the bivalents were closed at both ends. Inability to distinguish between auto‐ and allosyndesis resulted in two interpretations of genome relations. Either A. smithii is an alloploid with two of its four genomes similar to those of E. canadensis, or it is a segmental autoalloploid genomically unrelated to E. canadensis. The first interpretation is favored. Agropyron dasystachyum, or one of its close relatives, and E. triticoides are suggested as possible parents of A. smithii.
PHOTOPERIOD IN XANTHIUM POPULATIONS FROM TEXAS AND MEXICO
Authors: McMillan Calvin
Published: January 2018

Photoperiodic responses of Xanthium strumarium L. originating between 19° N in Mexico and 34° N in Texas varied among seedlings grown from seed under controlled conditions. The critical night lengths form a gradient from 9.5 hr in northern Texas to 10.75 hr in southern Texas and northeastern Mexico. Populations with critical night lengths of 9.5 and 9.75 hr showed a longer interval to flower bud formation under cooler temperatures (24 C day/15 C night) than under warmer temperatures (30 C day/24 C night). Three of four populations with a 10.75‐hr critical night length showed a shorter interval under the cooler temperature regime. Although the Texas populations demonstrate a strong correlation of photoperiodic response with latitude, the Mexico populations show diverse photoperiodic timing from approximately the same latitude. The study emphasizes that a combination of critical night length and ripeness‐to‐flower (maturity) response forms the basis for reproductive adaptation in different climatic regimes in Texas and Mexico.
THE NODULAR MYCORRHIZAE OF PODOCARPUS ROSPIGLIOSII
Authors: Furman Thomas E.
Published: January 2018

Podocarpus is a genus of southern hemisphere and tropical conifers which are often important timber trees in their respective ranges. Nodular short‐roots were early noted as being similar in gross aspect to legume nodules, and it was inferred that they are Rhizobium‐bearing symbiotic structures which fix atmospheric nitrogen. In histological section the nodular short‐roots of the Venezuelan species Podocarpus rospigliosii were shown to contain endotrophic mycorrhizae. In a Koch's Postulates test, a fungus isolated from Podocarpus induced the formation of nodular structures on aseptic seedlings. A Nitrogen16 test was negative for fixation of atmospheric N2. Recent work in New Zealand has shown comparable histology in other species of the genus. The mycorrhizae may be important in forestry practice, though not as a source of nitrogen.
AN ULTRASTRUCTURAL STUDY OF CELL DIVISION IN THE CAMBIUM
Authors: Evert Ray F. , Deshpande Bharati P.
Published: January 2018

The fine structure of dividing cambial cells of Ulmus americana and Tilia americana has been studied in material fixed in glutaraldehyde followed by osmium tetroxide. The cambia examined consisted of 7–9 rows of unexpanded fusiform cells, all of which had similar ultrastructural components. The fine structure and sequence of events of mitosis and cytokinesis in the dividing cambial cells apparently are similar to those of dividing cells in root tips and leaves. Of special interest was the observation that during cytokinesis, a broad cytoplasmic plate or phragmosome precedes the developing phragmoplast and cell plate through the dividing cambial cell. Smooth and coated vesicles derived from dictyosomes are associated with cell plate formation in these cells, smooth vesicles primarily with earlier stages of plate formation, and coated vesicles in later stages.
EFFECTS OF CULTIVAR AND PLANT AGE ON VEGETATIVE GROWTH OF THE STRAWBERRY, FRAGARIA ANANASSA
Authors: Jahn Otto L. , Dana Malcolm N.
Published: January 2018

Growth of strawberry plants (Dunlap, Sparkle, and Catskill) in the greenhouse was affected by the time of rooting of the runners in the field. This was shown by more rapid leaf and leaf‐area production, larger leaf size, more runners and root growth on the older compared to the younger runner plants. The oldest plants also produced the greatest number of flower buds, but the time of bloom was not appreciably affected. The growth responses of plants of different sizes were similar to those of plants of different ages. These growth responses were most apparent during the first stages of growth, but the resulting differences frequently persisted for several months. Significant differences between cultivars were also found. Initially the greatest leaf size and leaf area were produced by Catskill plants. Because of a higher leaf production rate, Sparkle plants eventually had the largest leaf area. Sparkle plants were the last to flower and also to initiate runner production. Dunlap plants were the first to flower and produced the largest number of flowers. In the field, leaf production records indicated responses from cultivars and plant age similar to those found in the greenhouse.
ULTRASTRUCTURE OF DRUSE CRYSTAL IDIOBLASTS IN LEAVES OF CERCIDIUM FLORIDUM
Authors: Price John L.
Published: January 2018

The ultrastructure of druse crystal idioblasts in palo verde leaves is similar in certain aspects to other crystal‐containing idioblasts, but also displays several notable differences. Although the crystal itself is dissolved during the preparative procedure, the druse idioblast is readily observable. The large crystal is contained in a tightly appressed vacuole in the center of the idioblast. Between the crystal vacuole and the cell wall there is a narrow stalk‐like connection which has the same substructure and staining characteristics as cell wall material. The membrane of this crystal vacuole and the idioblast plasmalemma stain asymmetrically, while other cellular membranes in the idioblast appear symmetrical. Much of the remaining cell volume is occupied by a ramified vacuome and a peripherally displaced nucleus. The plastids of the druse idioblast are markedly different from chloroplasts in adjacent parenchyma cells. The former lack the size, starch grains, and well‐developed grana of the latter. Idioblast mitochondria are similar in quantity and appearance to those of palisade cells, except for a greater number of cristae in the former. Dictyosomes, while rare in mesophyll cells, are quite common in the idioblast. These features suggest that the druse crystal idioblast is metabolically active and not dead at maturity.
INDEPENDENCE OF TISSUES DERIVED FROM APICAL LAYERS IN ONTOGENY OF THE TOBACCO LEAF AND OVARY
Authors: Stewart R. N. , Burk L. G.
Published: January 2018

Six different homoplastidic periclinal chimeras of tobacco carrying the plastogene DP1 were selected after somatic segregation in heteroplastidic seedlings. Direct observation of the plane of division in epidermal cells of young leaves, and the number and size of sub‐epidermal green spots on leaves with the Green‐White‐White (G‐W‐W) pattern of variegation, indicated that the ratio of periclinal to anticlinal divisions in L‐I during development of the lamina was 1:3100. The number of green and white seedlings obtained from the different chimeral branches indicated a similar frequency of periclinal divisions in development of the ovary. The arrangement of green and white tissue in mature leaves of the various chimeral types indicated the extent of participation by the three apical layers in the initiation of the buttress, development of the axis, and formation of the lamina. During development of the lamina there must be three independent initial‐groups present. L‐I and L‐II initials remain marginal, but early in the growth of the lamina the leading edge of tissue derived from L‐III becomes separated from the submarginal (L‐II) initials by the products of frequent periclinal divisions of the L‐II initials.
CONTROL OF THE INTERNODAL INTERCALARY MERISTEM OF CYPERUS ALTERNIFOLIUS
Authors: Fisher Jack B.
Published: January 2018

In the growing culm of C. alternifolius, surgical removal of parts indicated that the stimulus for the prolonged activity of the internodal intercalary meristem (IM) came from the matured leaves and upper internode and that buds were not involved in maintaining internodal growth. Decapitation of the culm resulted in cessation of internodal extension. Various growth regulators were applied to the decapitated internode, and both the total extension and growth rates were analyzed statistically. Gibberellin A3 (GA) and benzyladenine (BA) substituted for the excised parts in their effect on internodal extension. Indoleacetic acid (IAA) had little effect. (2‐chloroethyl) trimethylammonium chloride (CCC) inhibited internodal growth, and its effects were reversed by GA. IAA was antagonistic to BA but not to GA. BA and GA were somewhat antagonistic. The quantitative effects of growth regulators on epidermal and ground parenchyma cell length and number of interstomatal cells were examined. Extension induced by GA was due to both cell division and cell elongation in the IM. Cells were longer, and fewer stomates differentiated than in the control. In internodes induced to extend by GA + BA cell division, cell length, and stomate differentiation were similar to the control. The results indicate that prolonged internodal IM activity is maintained by cytokinins and gibberellins coming from the matured upper portions of the culm. Changes in the levels of these regulators during growth presumably result in the histological gradient in the internode.
THE MODE OF POLLINATION IN HABENARIA OBTUSATA (ORCHIDACEAE)
Authors: Thien Leonard B. , Utech Frederick
Published: January 2018

The role of mosquitoes and moths as pollinators of Habenaria obtusata was studied in northern Wisconsin during the summer of 1969. In each population studied, meter‐square quadrants were marked and the number of plants, flowers per inflorescence, rate and time of pollinia removed, and capsule set recorded. Carbon dioxide and modified New Jersey Light Traps were set during the flowering period to capture pollinia‐bearing insects. The study showed that female mosquitoes of the genus Aedes (particularly A. communis) and two species of Geometrid moths of the genus Xanthorhoe are important pollinators of H. obtusata. Pollination occurred during the last few days of flowering with an average of 18.0% of the pollinia removed and with 14.2% capsule set.
ORIGIN AND DEVELOPMENT OF PROTEIN GRANULES IN MAIZE ENDOSPERM
Authors: Khoo U. , Wolf M. J.
Published: January 2018

Protein granule development in the starchy endosperm of normal maize (inbred line, W46A) was studied with optical and electron microscopy. The granules were first observed 12 days after pollination as spherical deposits, usually single, within an enclosing membrane. They developed from vesicles produced by the endoplasmic reticulum and were formed both as small localized cisternal dilations and as enlargements at the ends of endoplasmic reticulum. Dictyosomes also appear to proliferate protein granule vesicles. The protein accumulated in the granules appears to be synthesized outside the membranes. Once initiated, the granules rapidly increase in size and number as the kernel develops; their final diameter ranges up to 2 μ. Immature granules stain with a variety of biological dyes in aqueous solution as well as with metal stains; mature granules stain lightly or not at all. At kernel maturity, the protein granules are embedded in a protein matrix.
CELL DIVISION IN RELATION TO CYTODIFFERENTIATION IN CULTURED PEA ROOT SEGMENTS
Authors: Torrey John G. , Fosket Donald E.
Published: January 2018

One mm‐thick segments cut 10–11 mm proximal to the root tip of germinating seeds of garden pea Pisum sativum were cultured in sterile nutrient medium containing auxin in the presence and absence of kinetin. In the absence of added cytokinin, pericyclic proliferation occurred, the cortical tissues showed no proliferation and were sloughed off, and a callus tissue of diploid cells was formed. In the presence of kinetin concentrations from 0.1–1.0 ppm cortical cells of the segments were induced to divide, beginning at the third day. From experiments with 3H‐thymidine incorporation at different times of culture, from cytological squash preparations and from histological sections it was shown that the cortical cells stimulated to divide by cytokinin underwent DNA synthesis prior to division, were polyploid, and following cell division rapidly underwent cytodifferentiation at 5–7 days to form mature tracheary elements. At 10 days, when over 300,000 new cells had been formed per segment about 16% of these cells had formed tracheary elements. It was concluded that cytokinin, together with auxin, was essential for the initiation of DNA synthesis in the cortical cells, for their subsequent division, and finally for their specific cytodifferentiation.
THE ROOT APEX OF MALVA SYLVESTRIS. I. STRUCTURAL DEVELOPMENT
Authors: Byrne John M. , Heimsch Charles
Published: January 2018

The apical organization of the primary root of Malva sylvestris was analyzed at several growth stages, beginning with the embryo, to determine the structural changes that occurred during growth. Seeds were germinated, and plants were grown under controlled conditions. There were three discrete groups of initials in the embryonic root: those of the central cylinder, cortex, and secondary columella. The secondary columella initials consisted of a plate of cells flanked by a ring of cortical initials. The lateral portion of the rootcap shared a common origin with the epidermis. During growth both the initials of the secondary columella and outer cortex produced rootcap cells. The first indication of the outer cortical initials participating in rootcap formation was observed in roots 3 cm long. In 6‐, 9‐, and 16‐cm roots the cellular continuity between the outer cortex and rootcap was marked, but in 23‐ and 33‐cm roots the histogenic continuity between the outer cortex and rootcap was not evident. In all growth stages the initials of the central cylinder and inner cortex retained their histogenic integrity.
THE ROOT APEX OF MALVA SYLVESTRIS. II. THE QUIESCENT CENTER
Authors: Byrne John M. , Heimsch Charles
Published: January 2018

Embryos and primary roots at various growth stages of Malva sylvestris were treated with H3‐thymidine to determine the presence of a quiescent center by autoradiography. The nearly complete absence of nuclear labeling in cells of the quiescent center at all stages of root growth suggested that it was established prior to germination. The quiescent center increased in size during growth, and the cellular changes in apical organization as identified in a related anatomical study occurred outside of its limits. These anatomical changes were caused by the production of rootcap cells by the initials of the secondary columella and outer cortex. Autoradiography confirmed that the secondary columella initials were not quiescent during all growth stages and the outer cortical initials were not quiescent in those growth stages in which the anatomical changes occurred. The concepts of the promeristem and protomeristem are discussed in relation to the quiescent center.
A FREEZE‐ETCHING STUDY OF THE RED ALGA PORPHYRIDIUM
Authors: Neushul M.
Published: January 2018

Freeze‐etched cells of Porphyridium cruentum and P. aerugineum closely resemble those fixed with glutaraldehyde and post‐fixed with osmium tetroxide. Freeze‐etching reveals diversity in the non‐membranous and membranous parts of the cell. All the membranes are asymmetrical. The application of a double‐replica technique illustrates how the two sides of several cell membranes fit together. Interpretation of fracture patterns through the thylakoids and stroma leads to the suggestion that the thylakoids are composed of repeating structural units. A model of the photosynthetic apparatus is proposed. It is suggested that the thylakoids of Porphyridium and other red algae are not always “free” but can be stacked much like those of other plants.
THE WOOL‐LIKE COVERING OF THE ROOTS OF LANNEA ALATA I. THE ORIGIN AND MORPHOLOGY OF THE WOOLY COAT
Authors: McQuade H. A. , Cumbie B. G. , Sheldrick D. L. W.
Published: January 2018

Lannea alata (Engl.) Engl., Anacardiaceae, a tree or shrub of East Africa, has roots covered with dense wool‐like hair. Cork cambium of the root produces a closely appressed cork from which the hairs (modified cork cells) arise. Cork cells and wooly hair are rich in sterol and carotin‐oid‐like compounds and have thick walls. It is suggested that the root wool plays a role in the soil‐air, soil‐water relations of Lannea alata and other plants.
THE INITIATION OF SPOROPHYTES BY OBLIGATE APOGAMY IN CHEILANTHES CASTANEA
Authors: Whittier Dean P.
Published: January 2018

The initiation of apogamous sporophytes in Cheilanthes castanea was recorded by daily photography of individual gametophytes. Whereas an ordinary embryo arises from a zygote, apogamous embryos of C. castanea originate from one to three initial cells which occur just behind the apical region of the prothallus. The initial (or initials) produce cells with small chloroplasts behind the sinus of the gametophyte. The appearance of cells with smaller chloroplasts than those normally found in gametophytes is the first indication that apogamy is occurring. The cells with small plastids produce a group of densely‐cytoplasmic meristematic cells. The size of the meristematic mass increases until shoot and root apices of the apogamous embryo are organized.
STYLE ABSCISSION IN THE CITRON (CITRUS MEDICA L.) AND OTHER CITRUS SPECIES: MORPHOLOGY, PHYSIOLOGY, AND CHEMICAL CONTROL WITH PICLORAM
Authors: Goldschmidt E. E. , Leshem B.
Published: January 2018

Style abscission was studied in detail in citrons (Citrus medica L.) and other citrus varieties. The course of style abscission was followed under orchard conditions and also in an “explant” system consisting of pistils implanted in an agar‐sucrose medium and maintained at 25 C in a humid chamber. Morphological and anatomical observations carried out with the explant system revealed a prominent swelling of cell layers proximal to the separation layer prior to abscission. Tests with explants from flowers of different developmental stages showed that before the end of anthesis only the ovaries are capable of performing abscission while style abscission is possible only at a later stage, presumably after fertilization had occurred. Ethylene was able to induce ovary abscission at later stages but could not induce earlier style abscission. Picloram (4, amino‐3,5,6‐trichloropicolinic acid) increased the percentage of style persistence in citron varieties which naturally tend to retain their styles. Picloram also induced style persistence in Valencia oranges and Eureka lemons, which naturally show 100 % style abscission. Hormonal determinations showed that the style had higher levels of auxin than the ovary but also higher levels of inhibitors, which increased towards the time of style abscission.
A NEW GENUS OF PROTOSTELIDS SHOWING AFFINITIES WITH CERATIOMYXA
Authors: Olive Lindsay S. , Stoianovitch Carmen
Published: January 2018

A new genus and species of the Protosteliida (Mycetozoa), Ceratiomyxella tahitiensis, was isolated from dead plant material—var. tahitiensis from Tahiti and var. neotropicalis from Brazil and Colombia. The sporocarps have deciduous spores borne singly on slender hollow stalks; zoocysts with anteriorly flagellate planonts are produced. The trophic stage is comprised of uninucleate to plurinucleate amoeboid cells and reticulate plasmodia; the uninucleate cells become flagellate in water. The prespore cells and spores are plurinucleate. Sexuality has not been demonstrated. Var. tahitiensis has globose spores and produces its zoocysts just after spore germination, whereas var. neotropicalis has subglobose spores and forms zoocysts later in the life cycle. The species is thought to show phylogenetic relationships with Ceratiomyxa, which was recently transferred to the Protosteliida by Olive.
A COMPARATIVE ANALYSIS OF CELL MORPHOLOGY IN MATURING TISSUES OF ROOTS FROM SHOCKED AND UNSHOCKED BULBS OF ALLIUM CEPA L.
Authors: Murray Sylvia A.
Published: January 2018

A shock pressure pulse of 60 pounds per square inch (psi; 4.22 kg/cm2) effectively inhibited root growth of onion bulbs. Morphological changes observed after shock included a reduction in cell number in transverse section, a decrease in cell length, a decrease in cell volume, and an increase in cell cross‐sectional area. Mitotic activity was consistently increased one day after shock, and this may have accounted for the increased cell number per millimeter of root tip segment 8 days after shock. The development of the tissues appeared normal after shock exposure; however, the tissue response to pressures seems to depend on whether they are exposed to prolonged confining pressures or a brief pressure pulse. Responses which were unique to shock treatment include a decrease in cell number in transverse section, reduced cell volume, and increased radial enlargement of the cell. These responses have not been observed under prolonged pressure treatment.
THE PICEA ABIES SHOOT APICAL MERISTEM IN CULTURE. I. AGAR AND AUTOCLAVING EFFECTS
Authors: Romberger J. A. , Tabor C. A.
Published: January 2018

Shoot apical meristems of Picea abies seedlings can be cultured on a relatively simple, defined, basal medium. Dome‐like explants initially about 200 μ tall, without externally obvious primordia, and having dry weights of about 3 μg, usually initiate 5–10 new primordia within a week. They typically show 10‐ to 30‐fold dry weight increases in three weeks. None of the 5,000 meristems cultured has produced any basal callus. Growth is strongly influenced by both the type and concentration of agar used to gel the medium. Dry weight yield increases as agar concentration decreases. This is probably partly due to increased diffusion rates of enzymes or other large molecules through more dilute agar gels but possibly also partly ascribable to unknown agarborne inhibitors. About half of the agar concentration effect can be eliminated by substituting glucose and fructose for sucrose in the medium. This suggests that diffusion of invertase through the agar gel in this medium may be a growth limiting factor. Growth of cultures is also promoted by autoclaving sucrose in the presence of the agar. The basis of this effect is not yet understood.
DEVELOPMENT OF THE WOODY PORTION OF THE ROOT SYSTEM OF BETULA PAPYRIFERA
Authors: Horsley Stephen B. , Wilson Brayton F.
Published: January 2018

Our ontogenetic analysis of paper birch root systems shows that the fate of a root tip is related to its relative primary xylem diam (PXD). Lateral root tips with an initial PXD less than about 25 % of the parent root PXD are ephemeral. Some tips having a PXD of more than about 25 % of the parent root PXD become the permanent portions of the root system, enlarging over time as they elongate. In seedling root systems, the primary root and first‐formed laterals are initially about the same size, and their PXD's all enlarge with increasing distance from the stem as the tips elongate to form the initial horizontal woody framework. Permanent lateral root branches with a large relative PXD develop after root tip injury, when the root tip is forced to grow in a curve, or from other unaccountable causes. Our observations show the importance of using relative diameters when classifying roots and when applying the concept of heterorhizy to paper birch root systems. Evidence points to the existence of some form of apical dominance in roots.
AN ULTRASTRUCTURAL STUDY OF CHLOROPLAST STRUCTURE AND DEDIFFERENTIATION IN TISSUE CULTURES OF STREPTANTHUS TORTUOSUS (CRUCIFERAE)
Authors: Sjolund R. D. , Weier T. E.
Published: January 2018

Cells of Streptanthus tortuosus callus tissue contain chloroplasts when cultured in a liquid medium in the light. Similar cells grown in the dark contain proplastids that fail to develop prolamellar bodies but do contain a complex of loosely‐associated membranes. When green, light‐grown cultures are cut into small pieces and subcultured to a fresh culture medium, they become bleached even though maintained under the same illumination. The fine structure of the chloroplasts and the chlorophyll content of the cells indicate a dedifferentiation of the chloroplasts to a proplastid state during the early culture period. The changes in the ultrastructure of the plastids are paralleled by a dedifferentiation of the vacuolate cells to a less differentiated, meristematic state. Subsequent growth in the light results in a re‐formation of chloroplasts and an increase in the chlorophyll content of the cells. The period of chloroplast redevelopment is associated with the re‐formation of large central vacuoles in the cultured cells. Invaginations of the inner membrane of the plastid envelope occur at all stages of plastid development and are not lost during the period of grana degeneration. The proplastids formed from the dedifferentiation of the chloroplasts contain a large number of these invaginations and the redevelopment of grana is associated with a change in the electron density of the invaginating membranes. The degradation of the chlorophyll‐containing membranes of the grana occurs during a period of rapid cytoplasmic synthesis induced by the fresh supply of nutrients in the culture medium. These results suggest that the high levels of nutrients may act directly on the chloroplasts and cause their dedifferentiation or that the rapid cell growth induced by the nutrients may cause a degradation of the membrane proteins in the grana of the chloroplasts and an incorporation of the released amino acids into non‐plastid components of the cytoplasm.
OBSERVATIONS ON ROOT‐PARASITISM IN CORDYLANTHUS (SCROPHULARIACEAE)
Authors: Chuang Tsan‐Iang , Heckard Lawrence R.
Published: January 2018

Eight species of Cordylanthus (Scrophulariaeeae: tribe Euphrasieae) representing the three major sections of the genus were successfully grown both with and without a host plant, demonstrating that the plants are facultative hemi‐parasites capable of completing their life cycle without a host under the favorable conditions of greenhouse culture. The plants are almost certainly parasitic in the wild. Even though haustorial connections were formed by Cordylanthus on the roots of all host plants provided, most species were more vigorous when growing with certain hosts (Quercus, Pinus, Helianthus) than with others (Plantago, Phleum). This indicates a difference in the ability of the parasite to obtain materials successfully from the various plants used as hosts. Natural hosts are inferred for 15 species of Cordylanthus from the presence of associated species in nature. The haustoria are exogenous in origin, being formed by dedifferentiation of several cells in the hypo‐dermal or subhypodermal layers of the rootlets. Anatomically the haustoria differ from those reported for other members of Euphrasieae in having secondary vascular structure and abundant connecting strands. The vascular structure of haustoria is composed mainly of specialized vessel elements. Root‐parasitism gives Cordylanthus the ability to grow in arid areas during the summer after most other annuals have died, thus successfully equipping the plants for survival and expansion in western North America.
ULTRASTRUCTURAL CHANGES ASSOCIATED WITH UTILIZATION OF METABOLITE RESERVES AND TRICHOME DIFFERENTIATION IN THE PROTOCORM OF VANDA
Authors: Ricardo Manuel J. , Alvarez Marvin R.
Published: January 2018

Certain aspects of protocorm development in Vanda were examined ultrastructurally. The parenchymal cells of the protocorm accumulate substantial quantities of lipid, protein, and carbohydrate reserves which disappear gradually with the senescence of the parenchymatous region. The proteinaceous reserves appear initially as discrete bodies which become intimately associated with clusters of small tubules. The tubules eventually disperse throughout the cytoplasm and disappear following depletion of the protein bodies. The lipid reserves also appear as discrete bodies and are associated with an electron dense, laminated inclusion which appears to increase in size with the disappearance of the lipid bodies. While plastids in the meristematic cells differentiate a well‐developed thylakoid system and contain little starch, those of the parenchymal cells contain large starch grains and numerous osmiophilic droplets and develop meager thylakoid systems. Membrane‐bound crystalline structures of hexagonal and rhomboid cross section occur frequently in the cytoplasm of senescent parenchyma cells. Trichome initials, which differentiate from the epidermis, contain few conventional organelles and exhibit numerous membrane‐bound structures containing many small crystalline inclusions. Numerous vesicles accumulate at the tips of the trichomes in spaces between the cell wall and the plasmalemma.
MORPHOLOGIC, CYTOGENETIC, AND ENZYMATIC VARIATION IN SACCHARUM SPECIES HYBRID CLONES DERIVED FROM CALLUS TISSUE
Authors: Heinz D. J , Mee Grace W. P.
Published: January 2018

Two populations derived respectively from callus tissue of sugarcane clones H 37–1933 and H 50–7209 were studied for differences in morphology, chromosome number, and four enzyme systems. Variations observed in morphological characteristics were not directly correlated with differences in enzyme systems. Greater variation in both respects was observed in plants from the H 50–7209 (a chromosomal mosaic) population than in plants from the H 37–1933 (chromosomally stable) population. Among 37 plants of H 50–7209, all but one had cell‐to‐cell variation in chromosome number. In all but one of these 36 variable plants, the overall range was 2n = 94–120. The exceptional plant had a range of 2n = 17–118. Among 8 plants of H 37–1933, all had 2n = ca. 106.
THE SHOOT‐GROWTH RHYTHM OF A TROPICAL TREE, THEOBROMA CACAO
Authors: Greathouse D. C. , Laetsch W. M. , Phinney B. O.
Published: January 2018

The shoot‐growth rhythm of tropical trees is a little understood phenomenon. Correlations of tree growth with environment, determined from field studies in the tropics, have been largely inconclusive, and few studies have been done under controlled environmental conditions. As an initial part of a project to study shoot‐growth rhythms in tropical trees this paper describes the rhythm in Theobroma cacao L. An individual shoot passes through alternate periods of growth and dormancy. The growth period is characterized by the expansion of leaves and elongation of the shoot. During dormancy the length of the shoot remains constant, and no new leaves expand. Shoot‐growth rhythm was divided into phases. Dissection of shoot tips from the various phases shows that the total number of leaves and leaf primordia in the shoot apex remains constant during the dormant period and does not increase until the onset of the growth period. This indicates that activity of the apical meristem as well as leaf expansion and shoot elongation are rhythmic. We found that the rhythm of shoot growth persists under controlled environmental conditions and that growth under these conditions is asynchronous, as it appears to be in the field. Our data strongly suggest endogeneity.
HALLETHECA RETICULATUS GEN. ET SP. N.: A SYNANGIATE PENNSYLVANIAN PTERIDOSPERM POLLEN ORGAN
Authors: Taylor Thomas N.
Published: January 2018

A new structurally preserved synangiate pollen organ is described from the upper Pennsylvanian (Mattoon Formation) of southeastern Illinois. The specimen of Halletheca reticulatus gen. et sp. nov. measures approximately 1.5 cm long by approximately 5.0 mm in diam, and consists of five elongate sporangial tubes equidistantly arranged around a solid central column, and embedded in a thin‐walled ground tissue. The vascular system consists of five terete bundles characterized by scalariform tracheids. Sporangia are thick‐walled and contain pollen of the Monoletes‐type. Ultrastructural studies of the pollen grain wall show it to consist of a uniform network of muri which branch and re‐unite to form small lumina. A comparison of the ultrastructure of the pollen grain wall of the new fructification is made with the wall organization found in similar pollen of Dolerotheca. Relationships between the new taxon and other presumed seed fern pollen organs differing in preservation mode are discussed.
ELECTRON MICROPROBE ANALYSIS OF SILICA IN EPIDERMAL CELLS OF EQUISETUM
Authors: Kaufman Peter B. , Bigelow Wilbur C. , Schmid Rudolf , Ghosheh Najati S.
Published: January 2018

Patterns of silica deposition on the outer epidermal cell walls of Equisclum arvense and E. hycmalc var. affine were examined by means of electron microprobe analysis. Silica is deposited primarily in discrete knobs and rosettes on the epidermal surface in E. arvense and essentially in a uniform pattern on and in the entire outer epidermal cell walls of E. hyemale var. affine. This markedly contrasts with patterns of silica deposition in internodal epidermal cells of Avena saliva (Gramineae) where silica is deposited primarily in cell walls and cell lumina, and to a much lesser extent, on the outer epidermal surface. Semi‐quantitative analysis with the electron microprobe shows that in intercalary meristematic cells of E. aruense, silicon is not present in any cells, but that in mature epidermal cells above the intercalary meristem it is present in significant quantities. The study thus suggests that silica deposition must be a very rapid process in Equisclum and Avena.
COMPARATIVE LEAF STRUCTURE OF AQUATIC POLYGONUM SPECIES
Authors: Mitchell Richard S.
Published: January 2018

A systematic study of leaf morphology and anatomy of native, aquatic Polygonum, species is presented, treating 60 populations propagated in a common greenhouse. On the basis of this study it is now possible to distinguish American Polygonum species by leaf characters alone. Taxa in section Persicaria are contrasted and also compared with representatives of sections Bistorta and Echinocaulon. A complete description, utilizing 40 leaf characters, is given for each taxon. Complex glands, designated valvate chambers, are shown to be a consistent feature of the P. punctatum species‐complex, whereas epidermal storage‐idioblasts are present only in certain populations of this group. All other species lack valvate chambers but possess idioblasts, which may reach a frequency of over 400/mm2 in'P. hirsutum. The plate‐like multicellular gland of P. opelousanum is found to occur sporadically in P. hydropiperoides, thereby losing its specific diagnostic value. Illucidation of the characteristic structure of this gland, however, lends evidence to discourage the theory that it is an abortive structure produced by a hybrid between glandular and non‐glandular species. Reticulate venation and unicellular trichomes separate members of section Bistorta from the smartweeds, but P. meisnerianum (section Echinocaulon) is shown to simulate leaf structure of the persicarias both internally and externally.
A MORPHOLOGICAL AND HISTOLOGICAL STUDY OF THE TOMATO MUTANT ‘CURL’
Authors: Smith Ann Trommershausen , Stebbins G. Ledyard
Published: January 2018

The dominant tomato mutant ‘Curl’ differs from normal plants in several striking respects including the following: misshapen laminar structures such as leaves, sepals, and petals; stunted petiole and rachis; and persistent growth of blade and stem tissue from the adaxial surface of the rachis. These tissues as well as others which appear morphologically normal show gross histological abnormalities. Also evident in sections of mutant tissue is the appearance of areas containing numerous crystalline inclusions and a lack of bodies showing a stainable starch reaction in palisade and mesophyll of leaves and in endodermis and pith cells of the stem.
THE FINE STRUCTURE OF THE TRIGGER HAIR IN VENUS'S FLYTRAP
Authors: Williams Mary E. , Mozingo Hugh N.
Published: January 2018

Trigger hairs of Dionaea muscipula fixed in glutaraldehyde and OsO4 were prepared for study in the electron microscope. Electron micrographs of the active zone of the trigger hair reveal three regions in which the cells differ in size, shape, and cytoplasmic content. Each region contains large numbers of protein bodies and mitochondria with densely packed tubular cristae. Vacuole‐like structures containing protein bodies or an anastomosing system of cisternae, or occasionally both, are also present. Found only in the indentation cells is a complex, whorled endoplasmic reticulum. A concentric lamellar arrangement of the endoplasmic reticulum around the vacuolar structures is often observed. The lateral walls of the indentation cells are disproportionately thick while end walls are thin. The basal walls of these cells contain many plasmodesmata. Plasmodesmata in the anticlinal and podium cells pass through constricted zones in the cell wall and are particularly numerous in the peripheral podium cells. The possible functional significance of these structures is discussed.
LEAF AND APICAL GROWTH CHARACTERISTICS IN TRITICUM
Authors: Evans Lance S. , Berg Arthur R.
Published: January 2018

Leaf initiation rate, leaf primordium growth rates, and apical volume growth rates were determined for seedlings of Triticum aestivum cv. Ramona 50 under controlled environmental conditions. Three leaf primordia are present in the caryopsis, and three more leaves are initiated within the first two weeks after germination with a mean plastochron length of 95.5 hr. Volume growth rates of the apical region were determined on six apices which had six primordia each. The mean radial expansion rate was 0.467/plastochron, and the vertical expansion rate was 0.457/plastochron. The volume expansion rate was 1.393/plastochron. The mean volume doubling time was 0.498 plastochrons or 47.1 hr.
EFFECTS OF RELATIVE HUMIDITY AND TYPE OF CONTAINER ON THE GROWTH OF F1 HYBRID ANNUALS IN CONTROLLED ENVIRONMENTS
Authors: Krizek Donald T. , Bailey William A. , Klueter Heeschel H.
Published: January 2018

The effects of three levels of relative humidity (40%, 65%, and 90%) and two types of containers (clay and plastic) on the seedling growth of three F1 hybrid annuals were determined after 14 days of controlled‐environment treatment. Forty percent relative humidity was severely limiting to the seedling growth of ‘Blue Blazer’ ageratum (Ageratum houstonianum Mill.), ‘Pink Cascade’ petunia (Petunia hybrida Vilm.), and ‘Double Eagle’ marigold (Tagetes erecta L.). Raising the relative humidity to 65% resulted in striking increases in fresh weight, dry weight, and leaf area, especially when clay containers were used. Height of the main shoot was increased significantly at 65% relative humidity but node number was influenced only slightly. Increasing the relative humidity further to 90% had no significant effect on fresh weight, dry weight, or percent dry weight for any of the three species, in either container. Leaf area was increased significantly at 90% only in ageratum seedlings grown in clay pots. Each species responded differently to the type of container used. The fresh weight and dry weight of petunia seedlings were significantly greater in plastic pots at every level of humidity while those of marigold seedlings were unaffected by the type of container used. Ageratum seedlings, on the other hand, had significantly greater fresh weights and dry weights in clay pots only at 90% relative humidity.
AN UNUSUAL FOSSIL FRUCTIFICATION FROM THE JURASSIC OF OAXACA, MEXICO
Authors: Delevoryas T. , Gould R. E.
Published: January 2018

A fructification with unusual branching arrangement, Perezlaria oaxacensis gen. et sp. nov., is described from the Middle Jurassic Zorrillo Formation of Oaxaca, Mexico. The sporangial heads are similar to the pollen‐bearing organs of several Mesozoic pteridosperms. The association of P. oaxacensis, as well as some isolated organs resembling the synangia of Caytonanthus, with glossopteroid foliage is noted.
THE CELL WALL RESIDUE OF FOSSIL WOOD FROM SENFTENBERG
Authors: Morey Philip R. , Morey Elsie D.
Published: January 2018

Cellulose was identified in tracheids of a fossil wood from Senftenberg on the basis of birefringence, staining, and solubility properties. Birefringence was intrinsic. The lignin cell wall component showed the usual solubility properties. However, an abnormal fluorescence indicated some incipient deterioration of lignin. Observation with the polarizing microscope suggested that specific tracheids of the late wood were attacked by cellulose‐destroying bacteria. Degraded tracheids occurred most frequently in close proximity to the early wood. This suggested that prior to compaction, decay organisms penetrated the specimen through the then uncrushed, wide conduits of the early wood tracheids. Penetration by microorganisms in the radial direction into the late wood occurred subsequently through the tracheid pit system. The concept that both of the major cell wall constituents, cellulose and lignin, function as progenitors of the coal substance is discussed.
THE DEVELOPMENT OF THE ACHENE OF POLYGONUM PENSYLVANICUM: EMBRYO, ENDOSPERM, AND PERICARP
Authors: Neubauer Benedict F.
Published: January 2018

A study was made of the ontogeny of the achene of Polygonum pensylvanicum L. from fertilization to maturity. The proembryo is classified as the Polygonum Variation, Asterad Type. Cotyledons are initiated three days after anthesis, and by the fifth day procambium is present in the embryo axis. At approximately seven days after anthesis, the embryo begins to curve and occupy a marginal position in the ovary. By ten days the first foliage leaf primordium is initiated at the stem apex of the embryo. At maturity the embryo consists of two cotyledons, a plumule composed of the stem apex and one leaf primordium, and a hypocotyl with a well‐developed radicle. Endosperm nuclei begin to divide before the first division of the zygote. Cell wall formation begins in the endosperm at the micropylar end of the embryo sac and proceeds toward the chalazal region. By the fifth day the endosperm is completely cellular, except for a basal projection; and a peripheral meristem has been established. At approximately ten days the peripheral meristem ceases periclinal cell division and becomes the aleurone. At the time of fertilization the ovary wall has its full complement of cell layers. The walls of the outermost cells elongate and become convoluted. Subsequent thickening and lignification of these cell walls produce the hard epicarp of the mature achene.
STRUCTURAL EVIDENCE FOR A THEORY OF VEIN LOADING OF TRANSLOCATE
Authors: Geiger D. R. , Malone J. , Cataldo D. A.
Published: January 2018

The ultrastructure of minor veins of Beta vulgaris was examined with reference to possible models for vein loading of translocate. Structural evidence was reviewed in the light of recent physiological observations as a basis for proposed mechanisms. Features which appeared to be of significance in formulating a model included the open, differentiated sieve plates, the predominance of organelle‐rich parenchyma cells, and the branched plasmodesmata connecting sieve tubes and parenchyma cells. The resulting model views cell to cell movement of photosynthate via the symplast to the specialized parenchyma cells. The actively accumulated sucrose appears to move from the specialized parenchyma cells into the sieve tubes via plasmodesmata in the lateral and end walls.
PEROXIDASE ISOZYMES: A MEASURE OF MOLECULAR VARIATION IN TEN HERBACEOUS SPECIES OF DATURA
Authors: Conklin Marie E. , Smith Harold H.
Published: January 2018

Leaf proteins of the 10 herbaceous species of the genus Datura were separated by electrophoresis in starch gels and stained to reveal peroxidases. A. total of 19 different sites of peroxidase bands was observed for the species as a whole. Developmental studies showed that the number of bands increased with age of the leaf during seedling growth as well as in more mature plants. Among species the number of band sites for one particular leaf (AL‐4) varied from 4 to 9. Each species pattern was unique, and no single peroxidase band was common to all the species. Based on considerations of interspecific cross compatibility and chromosomal rearrangements the c assical taxonomic division of the genus into three sections was further subdivided to give five groups. The degree of phylogenetic relationship for species within vs. between these groups was assessed for the peroxidase patterns by use of statistical methods based on a hypergeometric distribution model. The probability that the observed degree of band matching was due to chance was less among species within a group than between groups, thus indicating a closer genetic association which is in agreement with the relationships arrived at by more conventional methods.
ONTOGENY OF THE PALEOZOIC OVULE, CALLOSPERMARION PUSILLUM
Authors: Rothwell Gar W.
Published: January 2018

The ontogeny of the upper Pennsylvanian age gymnospermous ovule, Callospermarion pusillum, is described from petrifaction specimens collected at the Berryville locality in Illinois. Ovules exhibit a wide range of dimensional and structural features that indicate an extensive developmental sequence. Specimens range from ovules with indistinct zonation of the thin‐walled integument to those with thick‐walled cells of the sclerotesta. The apex of the fleshy nucellus in some specimens is preserved as a cellular mound, while in others a well‐formed cellular pollen chamber is present; still other ovules are characterized by a papery‐thin nucellus and pollen chamber wall. The megagametophyte of most specimens is represented by a hollow megaspore membrane that may be restricted to the base of the nucellus, or occupy the entire seed cavity. In a few specimens cellular gametophytes are preserved, and in one ovule archegonia with supposed eggs are also present. Variability in each of the features is compared with ontogenetic changes in comparable structures of living gymnospermous ovules and is correlated with ovule size. A developmental sequence for the fossil ovules is proposed.