bluuebunny/crossref_metadata_2025 huggingface dataset:
THE NUCLEAR CYTOLOGY OF BIVALENT AND RING‐FORMING RHOEOS AND THEIR HYBRIDS
Authors: Wimber D. E.
Published: January 2018

The structural hybridity of the chromosomes of Rhoeo spathacea (R. discolor) that produces a ring of 12 chromosomes at meiosis is probably maintained by a balanced lethal system active in the zygotic or embryonic stage. Bivalent‐forming plants have been identified that belong to the taxon R. spathacea var. concolor. In the clone studied the arm arrangement in R. s. var. concolor is very nearly the same as the arm arrangement in one of the balanced translocation complexes of R. spathacea.
CONTROL OF SEXUALITY IN GOLENKINIA
Authors: Ellis Richard J. , Machlis Leonard
Published: January 2018

Sperm formation can be induced in strains 929 and 930 of the oogamous genus Golenkinia by nutrient depletion, specifically the deprivation of either nitrogen or phosphorus, but not by a decrease in total molarity or by a change in pH. Nitrogen (or phosphorus) concentration plays a controlling role in the presexual vegetative growth and the actual period of induction. During the latter, the rate of gametogenesis is inversely proportional to the nitrogen level and can be completely stopped by nitrogen added as many as 8 hr after resuspension in a medium lacking nitrogen. White light of an intensity of 10,000 ergs per cm2 per second is required during the first 9 hr of resuspension in an inducing medium although a lower intensity is sufficient if given for longer periods. Sexuality in Golenkinia responds most strongly to red or blue light, indicating that photosynthesis is important in this process. Fertilization in strain 929 requires at least 0.001 m calcium. No evidence was found for the action of hormones either in sexual induction or in chemotactic sperm attraction.
THE FINE STRUCTURE OF THE DIGESTIVE GLAND OF VENUS'S FLYTRAP
Authors: Scala J. , Schwab D. , Simmons E.
Published: January 2018

The digestive gland of Venus's flytrap has been studied by light and electron microscopy. Cells of the gland contain dense protoplasm comprised of relatively large nuclei, granular endoplasmic reticulum, osmiophilic vacuolar inclusions and numerous mitochondria, Golgi bodies and plastids. The vacuolar inclusions are predominantly protein but are also sudanophilic, therefore containing some lipid material. They are similar in appearance to aleurone grains. The nuclear envelope is a porous, double‐membrane structure, the pores of which are approximately 900 A and have a dense granular appearance. Plastids contain dense fine‐grained stroma, several thylakoids, osmiophilic globules and a tubular complex. Gland cell walls have many complex‐shaped protuberances extending into the cytoplasm providing a very large internal surface area. The stalk and basal cells contain numerous lipid globules and the common wall between the two cells is traversed by numerous plasmodesmata. In general the digestive gland fine structure is discussed in relation to its function.
HISTOGENESIS OF THE ANDROECIUM AND GYNOECIUM IN DOWNINGIA BACIGALUPII
Authors: Kaplan Donald R.
Published: January 2018

A histogenetic investigation of the synandrous androecium and syncarpous gynoecium in the flower of Downingia bacigalupii Weiler (Campanulaceae; Lobelioideae) was undertaken for the purpose of comparing the modes of initiation, early growth and fusion in these floral whorls with that reported previously for the perianth in this species. Stamens are initiated as separate organs from the second tunica layer and underlying corpus regions of the concave floral meristem. Subsequent growth of stamens involves apical and intercalary growth in length and rudimentary marginal growth in breadth. Tissues of the four microsporangia originate from hypodermal sporangial initial cells and the filament is formed by intercalary growth at the base of the anther. Lateral fusion of stamens is ontogenetic and involves cuticular fusion of adjacent epidermal layers. The two emergent carpel primordia arise as crescentic organs by periclinal divisions in the second tunica layer and corpus zones. Carpel primordia also undergo apical and intercalary growth in length as well as extensive marginal growth in breadth. Radial growth in carpels is mediated by an adaxial meristem which shows its greatest concentration of activity at the carpel margins. Carpel fusion appears to be partially ontogenetic accompanied by zonal growth. Closure of the stylar canal is by the formation of a transmitting tissue derived from the protodermal layers of the adaxial carpel surfaces. A discoid nectary is initiated around the base of the style and formation of the inferior ovary is by intercalary growth of the base of the concave floral bud. The two parietal placentae originate as longitudinal outgrowths from the walls of the floral cup. Ovule initiation is simultaneous at first and then intercalary during subsequent elongation of the ovary. The ovules are anatropous, unitegmic and tenuinucellate. Stamen and carpel procambium shows a slight delay in differentiation when compared to that reported for the perianth and bract, but in all other respects carpels resemble other floral organs in their patterns of histogenesis and early growth. Stamens diverge from the other floral organs in their early pattern of growth, but a consideration of all features of their histogenesis suggests an appendicular rather than an axial interpretation of these organs.
THE EFFECT OF COTYLEDON EXCISION ON THE GROWTH OF PEA SEEDLINGS
Authors: Killeen Leslie A. , Larson L. A.
Published: January 2018

Pea plants grown under controlled conditions for 28 days were sampled nine times during this growth period. On each sampling day 80 plants were harvested. Cotyledons were excised from 40 plants and the root‐shoot axis allowed to continue growth. The other 40 plants were divided into roots, shoots, and cotyledons; the dry weights of alcohol‐water extracts and residues from these organs were determined. Shoot lengths, numbers of nodes, buds, flowers, and fruits of 28‐day‐old plants, whose cotyledons were excised at different times, were determined. These data indicate that cotyledon excision after the 13th day has no apparent effect on seedling growth, whereas excision before the 13th day reduces growth. Glucose‐U‐C14 supplied to attached cotyledons of 6‐ and 16‐day‐old seedlings resulted in no major difference in the distribution pattern of recovered label throughout the plant even though 16‐day‐old cotyledons were depleted of their normal endogenous food reserve.
THE ROOT APEX OF LINUM
Authors: Byrne John M. , Heimsch Charles
Published: January 2018

Several developmental stages of primary roots of 13 species of Linum were studied. The basic pattern of root apex organization in three species consisted of a single tier of cortical initials. Ten species had a basic pattern of two tiers of cortical initials. Variations, manifested by either an increase or a decrease in the tiers of cortical initials, were observed in some roots in those species that had a basic pattern of two tiers of cortical initials. Although these variations were interpreted as being ontogenetic, there was no total reorganization of the root apex. There was anatomical and cytological evidence that a quiescent center is established in Linum roots.
POLLINATION ADAPTATION IN PEDICULARIS CANADENSIS
Authors: Macior Lazarus Walter
Published: January 2018

During the spring of 1966 and 1967, operation of the pollination mechanism of Pedicularis canadensis L. flowers by nectar‐ and pollen‐foraging bumblebee (Bombus Latr.) queens was observed in an Iowa relict prairie and was recorded by high‐speed cinematography. The stigma and style were found to sweep the forager's pronotum crevice as head and tongue were introduced into the 12‐mm corolla tube. Pollen deposited in the crevice was not removed as the forager's middle leg only groomed pollen laterally deposited on head and scutum. Thirty corbicular pollen loads from 417 foragers collected on nine prairie plant species included pollen from Pedicularis canadensis, Aquilegia canadensis L., Dodecatheon meadia L., and two unidentified plants not found in the prairie. The pollination mechanism was considered closely adapted morphologically and phenologically to bumblebee queens of eight species found foraging on Pedicularis.
STUDIES ON FOSSIL AZOLLA: AZOLLA MONTANA, A CRETACEOUS MEGASPORE WITH MANY SMALL FLOATS
Authors: Hall John W. , Swanson Nancy Peake
Published: January 2018

Azolla montana is a new species from the late Cretaceous; it has a megaspore apparatus with a single large and conspicuous columella which resembles the floats of the megaspore apparatus of many extant species. The columella differs from true floats in being pilose, like the perispore of the megaspore body. The 10–20 small true floats are appressed to the columella, and are difficult to distinguish from it. It is suggested that the floats were derived, phyletically, by segmentation of the columella; the columella represents the primitive “float” of the megaspore apparatus.
INDUCED APOSPORY IN THE LIVERWORT BLASIA PUSILLA
Authors: Raudzens Livija , Matzke Edwin B.
Published: January 2018

Immature sporophytes of Blasia pusilla L. collected in the field were excised from the protective gametophytic tissues and cultured on a slightly modified Knop's agar substrate in microphytotrons. Under the experimental conditions the setae elongated and after 33½ to 6 weeks many began to give rise to from 1 to 20 or more aposporous outgrowths. These subsequently developed into young gametophytes. The apices were then cut off, sterilized, and grown on glucose‐mineral agar in aseptic culture. The resulting gametophytes were similar to haploid plants derived from spores in pattern and rate of growth, and in possession of rhizoids, ventral scales, lateral lobes, auricles, and stellate and discoid gemmae. They produced archegonia but no antheridia. The chromosome number of the aposporous plants was 18 in contrast to the normal haploid number of 9.
CHROMOSOME NUMBERS AND EVOLUTION IN NORTH AMERICAN SPECIES OF LINUM
Authors: Harris Betty D.
Published: January 2018

Among the North American species of Linum there are three basic chromosome numbers representing invasions from the Old World of three distinct evolutionary lines. N = 9 is found only in the blue‐flowered group represented in North America by two species, L. lewisii and L. pratense which are closely related to and may be conspecific with the Old World L. perenne. The basic number for the yellow‐flowered species is n = 18 which is characteristic of the Scabrella and Virginiana subgroups. The loss of chromosomes in the Neo‐mexicana (n = 13) and Sulcata‐Rigida (n = 15) subgroups suggests that the basic haploid number of 18 might be a polyploid derivative of an Old World ancestor with n = 9. The incidence of n = 9 among Old World species of Linum may indicate that this represents an ancestral condition. Linum catharticum has n = 8; this number and features of morphology and distribution suggest that it is not directly related to either the blue‐flowered or yellow‐flowered groups in North America but represents a separate introduction on this continent.
ARTIFICIAL HYBRIDIZATION BETWEEN DIFFERENT POLYPLOID LEVELS IN GLANDULARIA (VERBENACEAE)
Authors: Solbrig Otto T. , Passani Cornelius , Glass Roger
Published: January 2018

The hexaploid North American species Glandularia elegans has been crossed with the South American diploid species G. stellaroides, G. peruviana, and G. pulchella. Analysis of the behavior of chromosomes at meiosis in the hybrid indicates that the chromosomes of G. pulchella are similar to one of the genomes of G. elegans. Non‐homologous pairing and presence of multivalents also indicates that G. elegans is a segmental allohexaploid derived most likely from South American ancestors.
STRUCTURE AND GERMINATION OF BLASTOCLADIELLA EMERSONII RESISTANT SPORANGIA
Authors: Horgen Paul A. , Griffin David H.
Published: January 2018

Resistant sporangia of Blastocladiella emersonii were induced by the addition of bicarbonate, potassium chloride, sodium chloride, or ammonium chloride to the medium and by the exposure of the zoospores to ultraviolet irradiation. Mature resistant sporangia induced by all of these conditions exhibit similar areolate wall pitting. Under suitable conditions resistant sporangia in all cases examined germinated with the cracking of the outer sporangial wall, with the formation of exit tubes by the inner sporangial wall, and with the cleavage and release of zoospores through discharge papillae formed in the tips of the exit tubes.
A HISTOCHEMICAL STUDY OF ABSCISSION LAYER FORMATION IN THE BEAN
Authors: Rasmussen H. P. , Bukovac M. J.
Published: January 2018

In debladed bean petioles calcium and dry weight increased in the abscission zone during an induction period of 14 hr. Before the microscopic appearance of the abscission layer calcium decreased in the abscission zone and increased in the petiole. Dry matter began to decrease in both the abscission zone and the petiole 24 hr after deblading. The first visual change in the cells of the abscission zone was a swelling of the pectic materials of the cell walls. This was followed by breakdown of other cell wall components, i.e., non‐cellulosic polysaccharides and cellulose. The cellulose of the cell walls adjacent and distal to the abscission layer was found to be altered; however, no lignin was present during abscission layer development. The alteration of pectic materials, coupled with breakdown of cell wall components, resulted in the collapse of cells of the abscission layer just prior to separation. Auxin delayed abscission and also delayed the initial increase in calcium, the movement of calcium from the abscission zone to the petiole, and the decrease in dry weight.
TAXODIACEOUS BARK FROM THE UPPER CRETACEOUS OF ALBERTA
Authors: Ramanujam C. G. K. , Stewart Wilson N.
Published: January 2018

The structure of a piece of silicified bark of Taxodioxylon gypsaceum from near Medicine Hat in Southern Alberta is described. The fossil specimen probably came from Upper Cretaceous beds. The fossil shows affinities with the bark of modern Sequoia. Vectia luccombensis Stopes (1915) from the Lower Greensand (Aptian) of England probably constitutes an isolated piece of taxodiaceous bark, similar to the inner bark of the Alberta specimen.
CHROMOSOME NUMBERS IN THE COMPOSITAE: COLOMBIAN SPECIES
Authors: Powell A. Michael , King Robert M.
Published: January 2018

Chromosome numbers are presented for 76 species belonging to 35 genera of Compositae from Colombia. Thirty‐nine species and three genera, Espeletia (x = 19), Steiractinia (x = 14), and Vasquezia (x = 19), are reported for the first time. New base numbers or chromosome series are recorded in Baccharis (B. nitida, n = 25), Calea (C. caracasana, n = 24), and Liabum (L. mega‐cephalum, n = 10).
EFFECTS OF SUBCULTURING AND PHYSICAL CONDITION OF MEDIUM ON THE NUCLEAR BEHAVIOR OF A PLANT TISSUE CULTURE
Authors: Demoise Charles F. , Partanen Carl R.
Published: January 2018

A callus of the common garden peony, Paeonia suffruticosa, was subcultured on solid and liquid media and analyzed intensively for a period of 153 days in order to test the effects of subculturing and the physical conditions of culture on the mitotic cycle kinetics of a population of cells, particularly in relation to the degree of heteroploidy. The parameters investigated in the kinetic studies included mitotic index values, cell generation time, and the time required for the cell population to double. The mitotic index of Paeonia cells cultured in liquid medium was found to be about two and a half times higher than for those cultured on solid; successive subculturing did not affect the mitotic index on either type of medium. The most significant results of the study came from the chromosome count data, in which diploid and tetraploid cells fluctuated in predominance in successive subcultures, and the apparent earlier manifestation of polyploidy on liquid medium. Mitotic index, cell generation, and population doubling times remained constant throughout the study.
DEVELOPMENTAL ASPECTS OF THE SHOOT APEX, LEAF, AND BELTIAN BODIES OF ACACIA CORNIGERA
Authors: Rickson Fred R.
Published: January 2018

The final event of leaf ontogeny in Acacia cornigera is the production of a Beltian body at the tip of each rachis and pinnule. This structure serves as a food source for an ant, Pseudomyrmex ferruginea F. Smith, that lives in a mutualistic relationship with the plant. The mature Beltian body consists of an epidermis, hypodermis, cortex and central vascular bundle. Anatomical and cytohistological comparisons between the shoot apex and leaf ontogeny in A. cornigera and similar developmental aspects of the phyllode of A. longifolia Willd. and of the leaf of A. decurrens var. dealbata F.v.M. indicate that each type of photosynthetic organ is characterized by a different period of longevity of its group of sub‐apical initials. The phylogenetic history of Beltian bodies is also discussed.
NUCLEAR BEHAVIOR, SEPTATION, AND HYPHAL GROWTH OF ALTERNARIA SOLANI
Authors: King Stanley B. , Alexander Leonard J.
Published: January 2018

Nuclei of multinucleate hyphal tip cells divided almost synchronously. Nuclear division was followed by multiple septation during which the elongated hyphal tip cell was divided into several, generally multinucleate, cells. Within the same hypha a distinct growth pattern was not observed with respect to number, length, and nuclear number of cells formed with each successive nuclear division‐septation cycle. Hyphal branches originated and received nuclei from hyphal tip cells.
FINE STRUCTURE OF PHLOEM CELLS IN RELATION TO TRANSLOCATION IN THE COTTON SEEDLING
Authors: Shih C. Y. , Currier H. B.
Published: January 2018

When special precautions were taken to permit killing and fixation of sieve elements before they were cut, sieve pores were found to be open. Companion cells were shown to be highly resistant to freezing injury and less plasmolyzable than phloem parenchyma. Plasmodesmata connected parenchyma to parenchyma, parenchyma to companion cells, and companion cells to sieve elements. Their general absence between parenchyma cells and sieve elements points to a specific role of companion cells in sieve tube functioning. EM studies of these cells revealed an ER system which connects the central core of the plasmodesma to the sieve tube. This system may be responsible for active sucrose transport. Callose was always present on sieve plates of mature functioning sieve elements even with the most rapid killing and fixing possible. Extra callose promoted by heating (45 C) an intact stem segment was found to constrict the sieve pores almost completely. Constriction of plasmodesmata in lateral sieve areas also was evident. Fine structure analysis of the blocking mechanism is in accord with evidence obtained by tracer studies.
SEASONAL VARIATIONS IN RESERVE AND STRUCTURAL COMPONENTS OF PINUS RESINOSA CONES
Authors: Dickmann D. I. , Kozlowski T. T.
Published: January 2018

Changes in reserve materials, lignin, hemicellulose, and cellulose of 1st‐year conelets and 2nd‐year cones of red pine (Pinus resinosa Ait.) were studied by chemical extraction of the respective fractions. During the first 11 months after emergence of conelets, reserve materials, primarily carbohydrates, constituted approximately half of the dry weight of cones. Cellulose and hemicellulose contents were low but cells were highly lignified. During summer of the 2nd year of cone development, marked compositional changes occurred. A rapid surge of cone growth, possibly triggered by resumption of pollen‐tube growth and fertilization, occurred from mid‐June to early August and was accompanied by transformation of reserve materials into cellulose and, to a lesser extent, into hemicellulose and lignin. During this transformation, the thickening and lignification of cells responsible for the opening of cone scales probably occurred. The developing seeds also mobilized readily available cone reserves during this time.
COMPARATIVE DEVELOPMENTAL ANATOMY OF SHOOTS OF JUVENILE AND ADULT HEDERA HELIX
Authors: Stein Otto L. , Fosket Elizabeth B.
Published: January 2018

Apices of adult Hedera helix have a larger meristematic area, composed of smaller cells, than those of the juvenile shoots. In shoot tips of juvenile plants, cell divisions in the subapical area occur over a longer portion of the shoot, and cell division is continued for a longer period of time. These features are reminiscent of GA‐induced changes in other plants. It is suggested that in experiments designed to shift Hedera from the juvenile to the adult form, consideration should be given to agents which affect both rates of cell division and distribution of dividing cells in the young shoot.
PHYSIOLOGICAL EVIDENCE OF HYBRIDIZATION AND RETICULATE EVOLUTION IN PHLOX MACULATA
Authors: Hadley Elmer B. , Levin Donald A.
Published: January 2018

A comparative physiological analysis was conducted on a hybrid swarm involving P. maculata subsp. maculata and P. glaberrima subsp. interior. The population contained an array of segregates and introgressants. Hybrids displayed a high degree of heterogeneity in their physiological attributes, some characters being intermediate to, similar to, or transgressing those of the parental taxa. For example, both net photosynthetic rates and net photosynthetic/dark respiratory ratios were enhanced in the hybrids, and the level of enhancement was associated with the level of morphological intermediacy. Conversely, no enhancement was noted in either respiration rates or foliar fresh weight/ovendry weight ratios of the hybrids. Because of physiological imbalance, about one‐third of the hybrids were eliminated early in their development. Representatives of P. maculata subsp. pyramidalis, a putative stabilized derivative of hybridization between the above two parental species, were intermediate in most physiological features and closely resembled some natural hybrids. The data verify that the physiological features of subspecies pyramidalis can be assembled through recombination of the P. maculata and P. glaberrima genomes.
PHOTOPERIODIC ADAPTATIONS IN EUPATORIUM RUGOSUM
Authors: Cohn Robert J. , Kucera C. L.
Published: January 2018

Racial differences based on flowering response to several photoperiods were detectable in two widely separated populations of white snakeroot, Eupatorium rugosum Houtt. The most favorable photoperiod for advanced flowering in Georgia stocks was 12 hr, for those from North Dakota, 14 hr. The difference in latitude between these populations was approximately 12° and represents a mean difference of 75 days in the frost‐free season. Under noninductive photoperiod a 1‐hr interruption of white light in the middle of 15 hr of darkness stimulated floral initiation in North Dakota plants, whereas the same application at the beginning or at the end of the dark period failed to produce flower buds. The effect of red light (660 mμ) for 10 min given in the middle of the long night was similar to white light on the northern strain, and was negated by far‐red (730 mμ). Georgia stocks initiated flowering under 15 hr of darkness but were retarded by white light applied in the middle of the period, thus differing in basic response from North Dakota plants. Red light, in contrast to effects observed in North Dakota plants, retarded initiation of flower buds. This effect was offset by far‐red light. When compared with other studies on long‐day and short‐day species our results suggest that photoperiodic adaptations related to latitudinal distribution occur in white snakeroot. The North Dakota strain showed correspondence to long‐day types while short‐day tendencies were exhibited by Georgia plants.
SYNTHETIC HYBRIDS OF AGROPYRON ALBICANS X A. DASYSTACHYUM, SITANION HYSTRIX, AND ELYMUS CANADENSIS
Authors: Dewey Douglas R.
Published: January 2018

Emasculated crosses of Agropyron albicans Scribn. & Smith with A. dasystachyum (Hook.) Scribn., Sitanion hystrix (Nutt.) J. G. Smith, and Elymus canadensis L. yielded 34, 5, and 9 viable hybrid seeds from 66, 45, and 52 florets, respectively. The hybrids were for the most part morphologically intermediate between their respective parents. The parents behaved cytologically as allotetraploids, 2n = 28; but meiosis in A. albicans was somewhat more irregular than in the other three species. Chromosome pairing was good in all hybrids and indicated that the genomes of the parent species were closely homologous, but only the A. albicans × A. dasystachyum hybrids set seed. Although closely related, A. albicans and A. dasystachyum are not fully conspecific. Agropyron albicans was considered to be a subspecies of A. dasystachyum, as were A. riparium Scribn. & Smith and A. griffithsii Scribn. & Smith ex Piper.
CHARACTERIZATION OF DEVELOPMENT IN MAIZE THROUGH THE USE OF MUTANTS. II. THE ABNORMAL GROWTH CONDITIONED BY THE KNOTTED MUTANT
Authors: Gelinas D. , Postlethwait S. N. , Nelson O. E.
Published: January 2018

The maize mutant Knotted (Kn) is characterized by hollow, finger‐like outgrowths (knots) occurring mainly in the leaf blade. Portions of the ligule are displaced from the normal position to more distal locations within the blade. Knots apparently result from continued meristematic activity of isolated patches of cells surrounded by maturing tissue. Small knots appear to be centers of cell division. Epidermal cells overlying a small knot have been observed to undergo periclinal divisions. In addition to cell division, a reorientation of the axis of cell elongation is associated with knot formation. The pattern of knot distribution varies at different levels on the plant axis and within a leaf blade. From leaf 4 to leaf 10 or 11 the number of knots per leaf increases progressively, then declines in leaves initiated later. Knots always occur in association with lateral veins. The greatest number per vein occurs on the 3rd or 4th vein from the midrib. One plant developing from an X‐rayed heterozygous seed possessed a sector of normal tissue bisecting the plant in a vertical plane passing through the midrib of each leaf except the top two. The normal sector was knot‐free and had the ligule restored to the normal position. These observations suggest that cells with the characteristics of those from intercalary meristems occur throughout the blade in Knotted plants.
ON THE MOLECULAR STRUCTURE OF STARCH GRANULES
Authors: Frey‐Wyssling Albert
Published: January 2018

It is a problem how to fit the molecules of amylose and amylopectin into the ultrastructural apposition layers of starch granules which have a width of only 0.1μ. Stretched amylose chains with a length up to 1 μ can be ruled out. In addition to the proposal of Miihlethaler, who visualizes folded amylopectin chains, a model with a helical amylose chain is discussed. A helix with six glucose residues per turn would be compatible with the crystal lattice found by Kreger; and the disorder caused by this helix in the hexagonal lattice of the parallel side chains of the amylopectin would account for the low optical anisotropy of the starch granules as compared to the parallel β‐polyglucosan chains in cellulose. The proposed model, fitted into the 0.1 μ apposition ring of the starch granule, shows tangential strata with a layer repeat of about 80 A and a radial chain lattice with the fibre period 10.6 A; i.e., it shows a combination of a lamellar and a fibrous structure.
CALAMOPHYTON PRIMAEVUM: THE COMPLEX MORPHOLOGY OF ITS FERTILE APPENDAGE
Authors: Leclercq Suzanne
Published: January 2018

Although holotype material of Calamophyton primaevum Kläusel and Weyland has not been available since the Second World War, two fertile specimens of that species are in the personal collection of Professor H. Weyland. The purpose of this paper is to disclose the complexity of the organization of the fertile appendage. Formerly it was believed to consist of one segment that had dichotomized once and that had borne two pendulous sporangia, one at each branch. Numerous degagements of sporangia have revealed a complex morphology, consisting of one main segment divided into two secondary segments. Each supports three recurved side stalks which in turn bear 2 sporangia, a total of 12 sporangia. Each secondary segment terminates in two elongated projections. The morphology of the fertile organs is compared with that of two other species, C. bicephalum Leclercq and Andrews and C. forbesii Schopf. Great similarity of organization exists between C. primaevum and C. bicephalum. The possible synonymy of these two species is discussed.
MORPHOLOGICAL CONCEPTS: THEIR MEANING IN THE IDEAL MORPHOLOGY AND IN A COMPARATIVE ONTOGENY
Authors: Schüepp Otto
Published: January 2018

The quantitative relation between the apical meristem and the size of the youngest leaf and internode determines the character of the shoot as chain of phytons or as stem with adherent leaves. The pattern of phyllotaxy determines the course and the strength of descending leaf traces and their conjunction in a net or their interweaving in the palm trunk.
SOME COMMENTS CONCERNING THE REDUCTION OF THE GENUS THYSANOSPERMUM TO COPTOSAPELTA (RUBIACEAE)
Authors: van Steenis C. G. G. J.
Published: January 2018

The monotypic genus Thysanospermum Champ. ex Bth. from the Far East is reduced to the Indo‐Asiatic genus Coptosapelta. It is a marked example of the insufficient attention given to testing, emending, or revising old generic concepts which in the tropics are so often taken for granted from handbooks. It is suggested that large critical regional floras are most appropriate for curing this inadequacy which hampers progress in our understanding of both taxonomical insight and geographical distribution.
UNUSUAL SHOOT GROWTH PATTERN IN A TROPICAL TREE, OREOPANAX (ARALIACEAE)
Authors: Borchert Rolf
Published: January 2018

The tropical tree Oreopanax shows a number of characters usually considered as adaptations to a temperate climate combined with typically tropical features. This evergreen tree grows in flushes and forms “resting buds” between successive flushes. Because of the lack of marked seasons in the tree's habitat, the growth cycle shows almost no correlation with external factors. The terminal resting bud appears only after the rest period; new leaves within the bud are formed only during bud growth and bud break which last 10‐14 weeks vs. 2‐3 weeks for taxa in the temperate zone. Abscisic acid seems not to be involved in the induction of the rest period.
THE TRANSITION FROM FILAMENTOUS TO TWO‐DIMENSIONAL GROWTH IN FERN GAMETOPHYTES. II. KINETIC STUDIES ON PTERIDIUM AQUILINUM
Authors: Davis Bill D.
Published: January 2018

Gametophytes of the fern Pteridium aquilinum were incubated 3 days in red light and then transferred to white light. The sequence of events occurring after the transfer was as follows: a swelling of the apical region within 1 hr; a reduction in cell elongation after 5 hr; a series of one‐dimensional cell divisions between 10‐25 hr; and the initiation of two‐dimensional gametophytes after 25‐50 hr. The percentage of two‐dimensional gametophytes was proportional to the logarithm of the intensity of white light. The rate of elongation after 5 hr was inversely proportional to the logarithm of the intensity. The rates of cell divisions for one‐ and two‐dimensional gametophytes were proportional to intensity up to 240 and 120 ft‐c, respectively.
LEAF DEVELOPMENT, PHOTOSYNTHESIS, AND C14 DISTRIBUTION IN POPULUS DELTOIDES SEEDLINGS
Authors: Larson Philip R. , Gordon John C.
Published: January 2018

Rates of net photosynthesis and dark respiration and distribution of C14 from selected leaves were determined for young cottonwood (Populus deltoides) trees at different stages of development. Four series of five trees—one series for each of four treated leaf positions—were included in the study. Maximum C14 export occurred when a leaf had just attained maximum size. Lower stem leaves reached maturity quickly and began exporting photosynthate when demands of the young seedling were high. Leaves at higher stem positions matured more slowly, but senescence was also delayed so their effective export life was prolonged. Translocation from a newly exporting leaf was primarily upward to developing leaves and the apex. As a leaf at any one position aged, the translocation pattern gradually shifted from upward to bi‐directional and finally to a predominantly downward direction. Photosynthate translocated downward was incorporated into stem wood and roots. Maximum photosynthetic efficiency coincided with the downward shift of C14 export. Thereafter, net photosynthesis began to decline, at first slowly and then more rapidly. The patterns of photosynthesis, respiration, and C14 export associated with leaf age all varied according to leaf position on the stem.
THE DEVELOPMENTAL ANATOMY OF OPUNTIA BASILARIS. I. EMBRYO, ROOT, AND TRANSITION ZONE
Authors: Freeman Thomas P.
Published: January 2018

The large seeds of Opuntia basilaris Engelm. & Bigel. show an unusually high percentage of germination, followed by a rapid development of the seedling during the first 30 days of growth. The primary root has six xylem arms alternating with six phloem poles around a large central pith. Development of metaxylem opposite each of the primary phloem poles results in the formation of eight collateral bundles. Secondary and tertiary roots have four xylem and phloem poles with xylem developing to the center of the stele. The transition zone is characterized by a gradual disappearance of all but two of the primary xylem arms of the root. Metaxylem development in the central portion of the transition zone interconnects the protoxylem poles forming a primary xylem cylinder around the central pith. The collateral bundles pass through the transition zone essentially without change.
CELL DIVISION STUDIES OF THE SHOOT APEX OF DATURA STRAMONIUM DURING TRANSITION TO FLOWERING
Authors: Corson George E.
Published: January 2018

Seedlings of Datura stramonium L., although not photoperiodically sensitive, are useful for floral transition studies when raised in a growth chamber at a constant temperature of 25 C with a photoperiod of 8 hr of light (1,600‐2,000 ft‐c) and 16 hr of darkness. A terminal flower is formed after the seventh or eighth leaf primordium is produced. A constant rate of leaf initiation up to the time of flowering enables specific apical stages to be obtained and studied. Changes in the mitotic index, substantiated with calculated rates of cell division (measured by the accumulation of metaphases following treatment with colchicine) were studied in shoot apical zones during transition to flowering. Fluctuations in the mitotic index of each zone in the vegetative and transition apex with respect to apical stage as well as time of day were not statistically significant. The mitotic index of the summit zone of the vegetative apex was significantly lower than in the other zones whose mitotic indices were not significantly different from one another. During floral transition the mitotic index of the summit zone as well as the central zone (just below the summit zone) significantly increased while no significant changes were detected in the flank zones. It was shown that the mitotic index could be considered representative of the rates of cell division in Datura.
CONTROL OF TREHALASE SYNTHESIS IN NEUROSPORA CRASSA
Authors: Hanks David L. , Sussman A. S.
Published: January 2018

When an aconidial strain (STL6A) of Neurospora crassa is grown on carbon sources such as glucose, maltose, sucrose, etc., trehalase activity per unit weight of mycelium is very low. By contrast, media containing arabinose, glutamic acid, glycine, etc., which support growth only poorly, produce mycelium with very high trehalase activity. Retarding growth limiting the supply of a necessary nutrient, altering the pH and temperature, or adding toxic substances, however, does not derepress trehalase activity. Repression and derepression of trehalase was found to be reversible through the transfer of cultures to appropriate media. It is likely that the increase in trehalase activity results from de novo synthesis because labeled enzyme can be isolated from acrylamide gels after isolation from medium containing C14‐labeled leucine and after purification by other means. These experiments are interpreted in terms of catabolite repression which may be correlated with events during growth and conidiation.
IODOPHANUS, THE PEZIZEAE SEGREGATE OF ASCOPHANUS (PEZIZALES)
Authors: Kimbrough James W. , Luck‐Allen E. Robena , Cain Roy F.
Published: January 2018

The genus Iodophanus is a segregate of the coprophilous genus Ascophanus. It is characterized by the presence of callose‐pectic marked spores, diffuse amyloidy of asci, carotenoid pigments in paraphyses and excipular cells, and an Oedocephalum imperfect state in some species. It consists of 10 species which may be distinguished by (1) the nature of spore ornamentation, (2) size and shape of spores and asci, and (3) the arrangement of excipular cells. Four new combinations are made and two new species, Iodophanus helotinus and I. granulipolaris, are introduced. Keys, descriptions, and illustrations are given for all taxa treated herein.
A TULASNELLA PARASITIC ON AMOEBA TERRICOLA
Authors: Drechsler Charles
Published: January 2018

A microfungus attacking Amoeba terricola through germination of an adhering basidiospore is newly described as Tulasnella zooctonia. After intruding a branched haustorium into the animal, the spore extends one to three divergent procumbent hyphae externally, which at intervals give rise to obovoid hypobasidia. Some hypobasidia are oriented ascendingly and produce two to five globose epibasidia on the distal end, but many others lie prostrate on the substratum and form epibasidia on the exposed upper side. In either positional relation the epibasidia readily produce tapering sterigmata, each bearing an obovoid basidiospore provided with a conspicuous basal protrusion. Clamp connections have not been observed, nor any elaboration of waxy or gelatinous material.
CYTOGENETIC STUDIES OF CARTHAMUS SPECIES (COMPOSITAE) WITH 32 PAIRS OF CHROMOSOMES
Authors: Khidir M. Osman , Knowles P. F.
Published: January 2018

Two taxa of Carthamus, each with 32 pairs of chromosomes, merit specific status. C. baeticus (Boiss. & Reut.) Nym. is found on islands of and in countries surrounding the Mediterranean Sea, whereas C. turkestanicus Popov extends from western Turkey to Kashmir. Compared to C. baeticus, C. turkestanicus has wider leaves, wider and less divaricate bracts, larger heads with more florets and achenes, and florets with longer lobes. Their chromosomes differ to the extent that microsporocytes of their F1 hybrids had a reciprocal translocation in pachytene and a mean of over six, and up to 22, univalents at metaphase I. Pollen stainability and seed fertility were reduced in F1 hybrids.
FOSSIL LEAVES OF DENDROPANAX FROM EOCENE SEDIMENTS OF SOUTHEASTERN NORTH AMERICA
Authors: Dilcher David L. , Dolph Gary E.
Published: January 2018

As part of a reinvestigation of the Eocene floras from southeastern North America, a leaf form similar to some that were formerly placed in the genus Aradia has been identified as Dendropanax. Studies of the fine venation and cuticular characters have been important in this identification. This is the first report of leaf material of the genus Dendropanax in the fossil record.
TRICHOBLASTS IN HYDROCHARIS. I. ORIGIN. DIFFERENTIATION, DIMENSIONS AND GROWTH
Authors: Cutter Elizabeth G. , Feldman Lewis J.
Published: January 2018

In the root epidermis of Hydrocharis morsus‐ranae L. distinctive trichoblasts, which later grow out as root hairs, are formed by the unequal division of protodermal (immature epidermal) cells. The trichoblast is the more proximal product of this division. Trichoblasts differ from adjacent epidermal cells in manner of growth, in size, amount of cytoplasm, degree of succinic dehydrogenase and cytochrome oxidase activity, and in the structure of their plastids. Plastids in the trichoblasts gradually become colorless and of less complex structure with increasing distance from the root tip, in contrast to those in adjacent epidermal cells. The trichoblasts do not divide, but they elongate to a considerable extent in the most distal 3000 μ of the root tip and less extensively in the next 3000 μ. By contrast the sister cells and their products divide, but the individual products do not become markedly longer than the mother cell until situated more than 3000 μ from the root tip, when they undergo extensive elongation. The trichoblasts are thus characterized by delayed maturation and inhibition of cytokinesis; it is suggested that delayed maturation is a necessary prerequisite for differentiation of root hairs in this and other species.
CHANGES INDUCED BY LOW LIGHT INTENSITIES ON THE PROLAMELLAR BODY OF 8‐DAY, DARK‐GROWN SEEDLINGS
Authors: Weier T. E. , Sjoland R. D. , Brown D. L.
Published: January 2018

Etioplasts of 8‐day‐old, dark‐grown seedlings of Phaseolus vulgaris contain large, crystalline prolamellar bodies. The basic structural unit within the prolamellar body is a six‐pointed star (star module) with four tubules fusing at each of the nodes. With sufficient illumination some of the tubules are withdrawn and the crystalline prolamellar body transforms to a complex tangle of tubules, the reacted prolamellar body. In vivo spectrophotometry and electron microscopic observations were carried out on portions of the same leaves after varying periods of illumination with low light intensity. Protochlorophyllide transformation was normal. However, the structural changes are not closely tied to protochlorophyllide conversion. The pigment conversion is complete after 20 sec of illumination, but 80% of the prolamellar bodies are still in the crystalline form after 20 min of illumination. After 1 and 2 hr of illumination all prolamellar bodies are reacted. After 4 hr of continuous illumination 35%, and by 12 hr 60%, of the prolamellar bodies returned to the crystalline form. Spectrophotometric evidence and presence of grana show chlorophyll synthesis during this period. The coexistence of grana and the crystalline prolamellar body indicates that when insufficient photosynthetic membrane constituents are provided by the photo‐reactions, under low light intensity, the membranes of the reacted prolamellar body will be forced to reform a crystalline prolamellar body.
CONTROL OF PLASMODIAL FUSION IN A PANAMANIAN ISOLATE OF DIDYMIUM IRIDIS
Authors: Ling Hubert , Collins O'Neil Ray
Published: January 2018

Plasmodial fusion in a Panamanian isolate (Pan. 1) of Didymium iridis is controlled by at least six fusion loci. Only plasmodia with identical phenotypes for these six loci are capable of fusion. No evidence was obtained in this study to indicate that any one fusion locus more strongly affects the fusion process than any of the other loci. Control of plasmodial fusion in the Pan. 1 strain of D. iridis is similar to that found earlier for a Honduran strain (Hon. 1).
CHROMOSOME NUMBERS IN THE COMPOSITAE. XII. AUSTRALIAN SPECIES
Authors: Turner B. L.
Published: January 2018

Chromosome counts are reported for plants from 171 populations of Australian Compositae; most of these are first reports for the approximately 104 taxa distributed among 37 genera. New generic counts with base numbers indicated include: Astereae—Bellida (x = 9), Minuria (x = 9); Inuleae—Angianthus (x = 12, 13), Calocephalus (x = 7), Cephalipterum (x = 12, 14), Craspedia (x = 11), Gnaphalodes (x = 10), Gnephosis (x = 4, 12), Myriocephalus (x = 6), Isoetopsis (x = 17); Calenduleae—Tripteris (x = 8); and Artcoideae—Arctotheca (x = 9). Most of the counts were from the tribes Astereae (47) and Inuleae (95). The phyletic import of these data is discussed selectively and comparisons are made with the chromosomal variation found in the Australian desert Compositae with that found in the North American desert Compositae.
AN ISOLATION UNIT FOR SUPPLYING RADIOISOTOPES TO SPECIFIC SEGMENTS OF AN INTACT ROOT
Authors: Leister Geoffrey L. , Popham Richard A. , Burley J. William A.
Published: January 2018

A device useful for supplying radioactive ions to specific segments of intact roots is described. A small volume of aerated, radioactive culture solution may be circulated around an isolated segment of a root, while the remainder of that root and the other roots of the plant are exposed to non‐radioactive culture solution. Any root which does not have lateral roots extending beyond the epidermis can be inserted into the device without handling the root itself. No sealants are required to achieve a leak‐proof seal above and below the root segment. The use of flexible rubber membranes to isolate root segments causes no detectable damage to root cells where the membranes contact the root epidermis.
A SYSTEMATIC ANATOMICAL STUDY OF THE GENUS PERIDERIDIA (UMBELLIFERAE‐APIOIDEAE)
Authors: Chuang Tsan‐Iang
Published: January 2018

Certain anatomical features, especially of roots, leaves, and fruits, provide useful criteria for delimiting a genus and defining its component species. Most species of Perideridia have 1‐5 multistelic tuberous roots; however, P. Howellii and P. Kelloggii possess fascicles of up to 20 thickened fibrous roots, each of which is monostelic and composed of four or five primary xylem strands arranged alternately with isolated strands of secondary vascular tissues. The curious multistelic condition of the tuber apparently has not been reported for any other group of dicotyledons. An accessory vascular bundle located internally to the median collateral bundle of the leaf rachis is found in only three species of Perideridia. Depending on the species, the leaf mesophyll may be either dorsiventral or isolateral. In about two‐thirds of the species, the oil ducts of the fruit are solitary in the intercostal intervals and paired on the commissure; in the remaining one‐third they are more numerous in both situations, rising to 3‐5 in the intervals and 12‐13 on the commissure in P. Pringlei. Variation in number of oil ducts in the intervals assumes taxonomic importance because it has been used as a generic criterion in this group, but the present study shows no correlation between the number of oil ducts and other characters.
VARYING ENVIRONMENTAL FACTORS IN ORDER TO GROW INTACT LICHENS UNDER LABORATORY CONDITIONS
Authors: Pearson L. C.
Published: January 2018

Inasmuch as the cultivation of lichens in the laboratory has not been achieved through application of traditional techniques, viz, the establishment of optimum conditions of temperature, light, humidity, and other factors, an attempt was made to grow three kinds of lichens by varying some of these environmental factors. Over a 4.5‐mo period, weight was maintained, and apparently slightly increased, in Parmelia physodes by varying both humidity and temperature on a weekly basis. The lichen disks which had been exposed to the varied environment produced normal photo‐synthetic patterns after 3‐5 mo in the growth control chambers, but the patterns in those exposed to constant environment were abnormal. As evaluated either by dry weight or by photo‐synthetic pattern, the varied environment was beneficial both to P. physodes and to Xanthoria parietina. This was not true, on the other hand, in the case of Peltigera polydactyla. In all three species, however, the thalli exposed to the varied environment were the most normal in general appearance.