bluuebunny/crossref_metadata_2025 huggingface dataset:
THE USE OF TRITIATED THYMIDINE IN THE STUDY OF TISSUE ACTIVATION DURING GERMINATION IN ZEA MAYS
Authors: Stein O. L. , Quastler H.
Published: January 2018

Stein, O. L. (Montana State U., Missoula), and H. Quastler. The use of tritiated thymidinein the study of tissue activation during germination in Zea mays. Amer. Jour. Bot. 50(10): 1006‐1011. Illus. 1963.—Corn embryos were exposed to H3thymidine at various times during the first 80 hr of germination. An analysis of labeled nuclei was made from autoradiographs, and the number and position of mitoses were recorded. Those tissues which approach maturity during embryogeny (root cap, coleorhiza, scutellur node) are first to resume DNA synthesis (30 hr after soaking). No mitoses were observed in these tissues. In shoot and root, mitoses usually precede DNA synthesis, indicating that the nuclei of the dormant embryo have a DNA value of 4C(twice the diploid DNA) or more. The shoot begins its activity much later than the root (50 hr). The shoot apex was the last region to boeomo active, some 70 hr after initiation of the soaking treatment.
MORPHOLOGY AND CYTOLOGY OF SYNTHETIC HYBRIDS OF AGROPYRON TRICHOPHORUM X AGROPYRON CRISTATUM
Authors: Dewey Douglas R.
Published: January 2018

Dewey, Douglas R. (Utah State U., Logan.) Morphology and (cytology of synthetic hybrids of Agropyron trichophorum X Agropyron cristatum. Amer. Jour. Bot. 50(10): 1028–1034. Illus 1963.—Three hybrids were obtained from controlled crosses of pubescent wheatgrass, A. trichophorum (2n = 42), and hexaploid crested wheatgrass, A. cristatum (211 = 42). The hybrids were intermediate between the parent plants for all vegetative and spike characteristics observed. Under open pollination, 2 of the hybrids set 2 seeds each, and the other hybrid produced 60 seeds. Meiosis in the parent plants was basically regular. Average motaphase‐I chromosome associations were 0.09 I, 20.56 II, 0.05 III, and 0.16 IV per cell in the A. trichophorum parent, which was described as a segmental autoallohexaploid. The hexaploid A. cristatum parent averaged 0.18 I, 7.44 II, 0.81 III, 2.86 IV, 0.08 V, and 2.11 VI per cell at diakinesis and was described as an autohexaploid. Chromosome pairing in the hexaploid hybrid averaged 5.08 I, 8.94 II, 4.33 III, 1.11 IV, 0.27 V, and 0.05 VI per cell. On the basis of chromosome pairing in the parent species and their hybrids, it was concluded that 1 of the A. trichophorum genomes was partially homologous with the 3 genomes of hexaploid A. cristatum. Genome formulae for hexaploid A. cristatum, A. trichophorum, and their hybrids were represented as AAAAAA, A1A1B1B1B2B2, and AAAA1B1B2 respectively.
IN VITRO CULTURE OF FLORAL BUDS OF AQUILEGIA
Authors: Tepfer Sanford S. , Greyson Richard I. , Craig William R. , Hindman Joseph L.
Published: January 2018

Tepfer, S. S., R. I. Greyson, W. R. Craig, and J. L. Hindman. (U. Oregon, Eugene.) In vitro culture of floral buds of Aquilegia. Amer. Jour. Bot. 50(10): 1035–1045. Illus. 1963.—Floral buds at various stages of development, from early stages before sepal initiation to late stages with young carpel primordia present, were grown in culture on various agar media. A basic medium containing White's minerals, Nitsch's trace elements, coconut milk, sucrose, and assorted water‐soluble vitamins was developed for growth of the buds. The addition of indoleacetic acid, gibberellic acid, and kinetin to the basic medium extended the developmental limits of buds at nearly all stages and decidedly improved the continued development of carpels. On this medium buds produce all of their organ primordia, growing from early stages to about the size of flowers at anthesis, but will not develop unless the sepals are removed. This inhibiting effect of sepals is not understood at this time. Stamen development is consistently poor beyond the point of differentiation of anther and filament, even with the addition of hormones. The development of buds in culture is illustrated and compared with development in intact plants. With further improvement of the medium, it is hoped that these buds may be used for experiments testing theories of floral morphogenesis.
AN EXAMINATION OF THE EFFECTS OF ULTRACENTRIFUGATION ON THE ORGANELLES IN LIVING ROOT TIP CELLS
Authors: Bouck G. Benjamin
Published: January 2018

Bouck, G. Benjamin. (Yale U., New Haven, Conn) An examination of the effects of ultracentrifugation on the organelles in living root tip cells. Amer. Jour. Bot. 50(10): 1046–1054. Illus. 1963.—Excised pea roots were centrifuged at 20,000 g for various periods to determine the speed and order of stratification of living plant organelles; 20,000 g for 24 hr at 6 C seems to produce the most consistent layering with least damage to the organelles or to the root as a whole. The recovery of the cells was then followed to determine how fast and in what order the organelles achieve a random redistribution. Rough endoplasmic reticulum seems slow to stratify in its ultimate position at the centrifugal pole but is among the first of the organelles to reorient after centrifugation. Proplastids, large vacuoles, and the nucleolus are slow to recover from centrifuging, but after 8 hr of recovery only the nucleolus and very large vacuoles show indications of a previous layering. Within 12 hr after removal of the root from the centrifuge, growth (in length) of the whole root could be measured.
NATURAL HYBRIDIZATION AMONG FOUR SPECIES OF BAPTISIA (LEGUMINOSAE)
Authors: Alston R. E. , Turner B. L.
Published: January 2018

Alston, R. E., and B. L. Turner. (U. Texas, Austin.) Natural hybridization among four species of Baptisia (Leguminosae). Amer. Jour. Bot. 50(2): 159–173. Illus. 1963.— Interspecific hybridization involving 4 species of Baptisia (B. leucophaea, B. sphaerocarpa, B. nuttalliana, and B. leucantha) has been studied by means of extensive field work and subsequent morphological and chromatographic analyses. As a result of these studies, numerous hybridizing populations involving any 2, 3 and, in 1 instance, 4 species have been located. Near Dayton, Texas, all 4 species and all 6 of the possible 2‐way hybrid combinations have been found in a single field. Approximately 125 different chemical compounds have now been detected in the 4 species. Many of these compounds serve as species specific markers useful in the validation of specific hybrid types. Hybrids between B. leucophaea and B. sphaerocarpa and between B. leucophaea and B. nuttalliana are numerous, and in these large hybrid swarms a chromatographic and morphological analysis of population structure is possible. The former combination provides an excellent opportunity for the utilization of chemical markers as criteria for introgressive hybridization. The hybrid B. leucantha × B. sphaerocarpa is frequently encountered and contains a large number of compounds species‐specific for one or the other parental species. The other 3 hybrid types have been found infrequently. Certain hybrid types are generally similar morphologically (e.g., B. leucantha × B. sphaerocarpa as opposed to B. leucantha × B. nuttalliana), and chromatographic techniques are of great value in the absolute identification of such plants, especially in complex populations where backcrossing further complicates the interpretation of the background of a plant from exomorphic features alone.
VASCULAR SUPPLY AND STRUCTURE OF THE OVULE AND ARIL IN PEONY AND OF THE ARIL IN NUTMEG
Authors: Camp Wendell H. , Hubbard Mary M.
Published: January 2018

Camp, Wendell H., and Mary M. Hubbard. (U. Connecticut, Storrs.) Vascular supply and structure of the ovule and aril in peony and of the aril in nutmeg. Amer. Jour. Bot. 50(2): 174–178. Illus. 1963.—Examination of the placental region in the carpel of Paeonia indicates a complexity and super‐abundance of vascular supply beyond that usually found in angiosperms and certainly more than is necessary for adequate nutrition and water supply of the ovules. From this it is concluded that the ovules once were borne on a larger and more complex structure than the present carpel. Vascular strands leading to the aril and the hypostase are interpreted as being relictual. The large multifid aril of Myristica has a well‐developed vascular system composed of several sizes of branched bundles.
RED LIGHT, AUXIN RELATIONSHIPS, AND THE PHOTOTROPIC RESPONSES OF CORN AND OAT COLEOPTILES
Authors: Briggs Winslow R.
Published: January 2018

Briggs, Winslow R. (Stanford U., Stanford, Calif.) Red light, auxin relationships, and the phototropic responses of corn and oat coleoptiles. Amer. Jour. Bot. 50(2): 196–207. Illus. 1963.— Red light decreases the phototropic sensitivity of corn (Zea mays Burpee ‘Golden Cross Bantam’) and oat (Avena saliva ‘Victory’) coleoptiles. The decrease is reflected by a shift of the curve ploting log dosage vs. response to higher dosages, as described in the literature. In the absence of red light treatment, 1,000 meter‐candle‐seconds (mcs) white light induces first negative curvature in oats and almost no curvature in corn, which appears to lack the mechanism for first negative curvature. Immediately following a 2‐hr red light treatment, the same white light dosage induces almost maximum first positive curvature both in corn and in oat coleoptiles. The increase in curvature obtained reflects the decreased phototropic sensitivity of both plants shown by the dosage‐response curve shift. After red treatment, the effect of red light remains maximal for an hour, decaying to the level of non‐red‐treated plants within another 2 hr. Red light suppresses auxin production by corn coleoptiles. The effect decays after the end of red treatment. Both changes follow time courses parallel to those for the phototropic sensitivity changes. The 1,000 mcs light dosage induces lateral transport of auxin both in red‐treated and untreated corn coleoptiles, despite the lack of curvature of the latter. Red light does not induce a circadian rhythm for the phototropic sensitivity changes in oats, is not effective if administered after phototropic induction, and its effect is probably mediated by phytochrome. The hypothesis, not original with this paper, that red light induces an increase in the amount of pigment mediating second positive curvature most closely accounts for the results obtained. Pertinent literature is discussed.
CONTRIBUTIONS TO THE MORPHOLOGY OF LEPTOCHILUS AND PARALEPTOCHILUS
Authors: Nayar B. K.
Published: January 2018

Nayar, B. K. (Natl. Bat. Gard., Lucknow, India.) Contributions to the morphology of Leptochilus and Paraleptochilus. Amer. Jour. Bot. 50(4): 301–308. lllus. 1963.—Morphology of L. axillaris and P. decurrens is described; L. axillaris is epiphytic, possessing a wide creeping, soft, parenchymatous rhizome, covered sparsely by peltate paleae, while P. decurrens is rupicaulous, with a short, brittle rhizome having slender sclerenchyma strands and densely covered by basally attached paleae. The vascular cylinder of the rhizome is dictyostelic and composed of a large number of closely placed, thick, vascular bundles with characteristic, thickened, endodermal cells in L. axillaris; it is dictyostelic and composed of a few, slender, distantly placed vascular strands in P. decurrens. Leaf traces are multiple strands which in P. decurrens originate in alternate succession from either side of the dorsal median vascular bundle of the rhizome, but in L. axillaris, from the lateral vascular bundles of the rhizome. The branch traces are paired strands which are lateral in the former and medianly placed in the latter. Scattered sclerenchyma strands occur in the stipe of P. decurrens. Paraphyses are absent in P. decurrens, but filamentous paraphyses occur in L. axillaris. The spores are bilateral and smooth‐walled in both, and the prothalli are of the branched, ribbonlike type developing as in Colysis. Prothalli are naked in L. axillaris, but bear sparse mammillate marginal hairs in P. decurrens.
THE STRUCTURE AND REPRODUCTION OF DUDRESNAYA HAWAIIENSIS SP. NOV. (RHODOPHYTA)
Authors: Lee Robert K. S.
Published: January 2018

Lee, Robert K. S. (U. Hawaii, Honolulu.) The structure and reproduction of Dudresnaya hawaiiensis sp, nov. (Rhodophyta). Amer. Jour. Bot. 50(4): 315–319. Illus. 1963.—A description of Dudresnaya hawaiiensis sp. nov. of the Dumontiaceae, Cryptonemiales, is given. The genus, which includes 8 previously described species, has heretofore not been reported from the Hawaiian Islands. Dudresnaya hawaiiensis is distinguished from other species of the genus by its thick, short stipe, its closely clustered main branches, and its very dense covering of slightly flattened, obovate branchlets. The structure of the carpogonial and auxiliary‐cell branches and the development of the carposporophyte and of the spermatangia are discussed and compared with those in other species of the genus.
SOME EFFECTS OF KINETIN ON THE GROWTH AND FLOWERING OF INTACT GREEN PLANTS
Authors: Wittwer S. H. , Dedolph R. R.
Published: January 2018

Wittwer, S. H., and R. R. Dedolph. (Michigan State U., E. Lansing.) Some effects of kinotin on the growth and flowering of intact green plants. Amer. Jour. Bot. 50(4): 330–336. Illus. 1963.—Dry matter accumulation of aerial parts, and heights of tomato, cucumber, and pea plants were markedly reduced when kinetin was incorporated into the culture solution root medium in concentrations ranging from 10–5 to 10–7 M. Concentrations which suppressed top growth (height, dry weight) generally had lesser effects on root growth and, in some instances, enhanced it. Thus top/root ratios were greatly reduced and approached unity in kinetin‐treated peas and tomatoes. Flowering was inhibited in tomatoes and accelerated in peas. There were marked changes in root morphology, including the formation of pseudonodules. Kinetin had an effect which was opposite to that of gibberellin on internode elongation, root extension, top/root ratios and flowering of dwarf peas. N6‐benzyladenine was more active than kinetin in suppressing the growth of intact green plants. The data show that kinetin can markedly alter the behavior of intact plants when absorbed by the roots from culture solutions in which the concentrations are comparable to those which are biologically active on explants.
CYTOGENETIC STUDIES IN CLARKIA, SECTION PRIMIGENIA. I. A CYTOLOGICAL SURVEY OF CLARKIA AMOENA
Authors: Snow Richard
Published: January 2018

Snow, Richard. (U. California, Davis.) Cytogenetic studies in Clarkia, section Primigenia. I. A cytological survey of Clarkia amoena. Amer. Jour. Bot. 50(4): 337–348. Illus. 1963.—Clarkia amoena (2n = 14) shows great cytological diversity based on reciprocal translocations. About ½ the plants sampled were heterozygotes; in 2 of the subspecies the frequency was as high as ⅔. The metaphase configurations were varied, including rings of 4, 6, 8, 4 + 4, 6 + 4, and more unusual types forming a chain of 3 + a univalent or a chain of 4 + a univalent. The latter have only 13 chromosomes but are not true monosomies. Some plants with supernumerary chromosomes were found, in addition to a plant with only 12 chromosomes which was derived from a “monosomic” type. From crosses of various homozygous lines to a standard strain, it was found that the standard end arrangement of chromosomes occurs widely and commonly throughout the species. A minimum of 7 different end arrangements, giving a ring of 4 with the standard strain, and 1 giving a ring of 6, account for the chromosome pairing found in interstrain crosses. No doubt more would be found with further testing. Some of the translocations may be components of adaptive polymorphic systems, though there is no proof of this yet. No balanced lethal systems similar to those in the closely related genus Oenothera were found.
STUDIES ON THE ONTOGENY OF THE DWARF MISTLETOES, ARCEUTHOBIUM. I. EMBRYOGENY AND HISTOGENESIS
Authors: Cohen Leon I.
Published: January 2018

Cohen, L. I. (Washington State U., Pullman.) Studies on the ontogeny of the dwarf mistletoes, Arceuthobium. I, Embryogeny and histogenesis. Amer. Jour. Bot. 50(4): 400–407. Illus. 1963.—A complete developmental study on the origin and organization of the main tissue systems in the embryo of Arceuthobium reveals a greater degree of internal differentiation in the mature embryo than hitherto reported. The mature embryo consists of rudimentary cotyledons, a well‐defined hypocotyl and a highly organized radicle. The latter develops from the remaining undifferentiated portion of the globular embryo soon after the embryonic cortex and procambium are differentiated. The radicular promeristem is organized into 4 initiating zones: (1) a uniseriate layer of apical surface initials; (2) a subapical zone of central initials; (3) a peripheral zone; and (4) a zone of procambium initials. Comparison between the dwarf mistletoe embryo and those of several nonparasitic angiosperms indicates that their ontogenies, in many respects, are essentially similar.
STUDIES ON THE ONTOGENY OF THE DWARF MISTLETOES, ARCEUTHOBIUM. II. HOMOLOGY OF THE ENDOPHYTIC SYSTEM
Authors: Cohen Leon I.
Published: January 2018

Cohen, L. I. (Washington State U., Pullman.) Studies on the ontogeny of the dwarf mistletoes, Arceuthobium. H. Homology of the endophytic system. Amor. Jour. Bot. 50(5): 409–417. Illus. 1963.—Development of the seedling in Arceuthobium, as well as the mode of penetration and infection, is described. The promeristem of the root apex of the seedling, as in the embryo, is composed of 4 zones: (1) a uniseriate layer of apical surface initials; (2) a subapical zone of central initials; (3) a peripheral zone; and (4) a zone of procambial initials. After germination, the seedling grows on the host surface until the root apex is confronted by a spur shoot or by a fragment of raised bark. The root apex becomes attached to the host by means of a massive holdfast. It is the procambial initials which actually invade the host tissue. After penetrating the host, the individual procambium initials proliferate in the cortex, each giving rise to a cortical strand. It was concluded that the endophytic system of Arceuthobium cannot be interpreted in terms of classical concepts of plant homology; it is, in fact, an organ sui generis.
EXPERIMENTAL INDUCTION OF VASCULAR TISSUES IN CALLUS OF ANGIOSPERMS
Authors: Wetmore Ralph H. , Rier John P.
Published: January 2018

Wetmore, Ralph H. (Harvard U., Cambridge, Mass.), and John P. Rier. Experimental induction of vascular tissues in callus of angiosperms. Amer. Jour. Bot. 50(5): 418–430. Illus. 1963.—Callus tissues in established maintenance culture lack morphological and physiological organization. Such callus consists of homogeneous parenchyma. Movement of auxin and sugar, therefore, must be along diffusion gradients. The only vascular tissues occurring in callus are induced. Experimental induction of vascular tissues has been successful in callus of 3 sp. of the Oleaceae: a tree, Fraxinus americana, and 2 shrubs, Syringa vulgaris and Ligustrum vulgare; another tree, Salix purpurea, var. lambertiana; a vine, Parthenocissus tricuspidata; and an herb, Helianthus tuberosus. In each of these species, an auxin (IAA or NAA in these studies) and a sugar (sucrose or glucose in these studies) prove necessary for the induction and complete differentiation of xylem and phloem in callus tissues. Varying concentrations of sugar alter the proportions of xylem to phloem: low concentrations, 1.5%–2.5%, favor xylem formation; high, 3%–4%, favor phloem. Middle concentrations, 2.5%–3.5%, favor the presence of xylem and phloem, usually with a cambium between. The almost universal association of xylem and phloem may have its explanation in this middle concentration of sugar. Grafting of apices into callus or direct application of appropriate concentrations of an auxin and a sugar in agar to the surface of callus causes nodules of vascular tissue to be formed, mostly in a circular pattern when seen in section transverse to the axis of orientation of the callus in the medium. The diameter of this circle varies directly with the auxin concentration at the place of application, 0.05 mg/liter giving a narrow, and 1 mg/liter, a wide pith. In individual nodules, xylem is characteristically oriented towards the center of the callus and the phloem towards the outside. Variable cross‐sectional views of nodule distribution in calli under different treatments suggest experimental approaches to understanding stelar patterns. The induction and differentiation in callus of xylem and phloem tissues has no relation to conduction. Any use of vascular tissues can occur only after their induction.
CHROMATOGRAPHIC INVESTIGATIONS ON THE ALKALOID CONTENT OF NICOTIANA SPECIES AND INTERSPECIFIC COMBINATIONS
Authors: Smith Harold H. , Abashian Dorothy V.
Published: January 2018

Smith, H. H., and D. V. Abashian. (Brookhaven Natl. Lab., Upton, N. Y.) Chromatographic investigations on the alkaloid content of Nicotiana species and interspecific combinations. Amer. Jour. Bot. 50(5): 435–447. Illus. 1963.—Alkaloid content was analyzed by paper‐partition chromatography in the following Nicotianas: (1) 52 species representing all taxonomic sections and centers of geographical distribution; (2) 35 two‐species combinations including 1 species of hybrid origin, 5 F1 interspecific hybrids, 24 amphiploids and 5 sesquiploids; (3) 14 three‐species combinations including 6 hybrids between an amphiploid and a third species, and 4 different 3‐species combinations with doubled chromosome number; (4) 2 four‐species combinations. Most of the species contained predominantly 3 identified alkaloids: nicotine, nornicotine and anabasine. In addition, at least 6 other alkaloids, that are separable but which were not identified chemically, are characteristic of the genus and are present in varied but characteristic patterns in each species. In hybrid combinations the content with regard to the unidentified alkaloids was observed to be the same as both parents, the sum of the parental patterns, a new alkaloid appearing, or, most frequently, one or more of the parental alkaloids missing in the hybrid. Among the identified alkaloids, anabasine was most frequently dominant to the other 2 in hybrids, and nornicotine production was most frequently either dominant or partly dominant to nicotine production. No simple basis for the inheritance of alkaloidal contents was clearly evident, nor wore there clearly defined associations between phylogenetic position and the alkaloids observed. Studies on the 6 or more alkaloids, in addition to nicotine, nornicotine and anabasine, which are known to be characteristic of the genus, offer extensive materials for research on alkaloid biosynthesis.
TRACHEARY ELEMENTS OF THE FERNS. I. FACTORS WHICH INFLUENCE TRACHEID LENGTH; CORRELATION OF LENGTH WITH EVOLUTIONARY DIVERGENCE
Authors: White Richard A.
Published: January 2018

White, R. A. (U. Michigan, Ann Arbor.) Tracheary elements of the ferns. I. Factors which influence tracheid length; correlation of length with evolutionary divergence. Amer. Jour. Bot. 50(5): 447–455. 1963.—To determine the variability of tracheid lengths in ferns, several factors were surveyed which might modify them. On the basis of average lengths based on from 100 to 300 measurements, the following factors were found to affect fern tracheid length significantly: location in the plant, stage of maturation of the plant, length of the internode, ploidy, and habitat. These factors were considered when a statistical analysis was made of the relationship between tracheid length and taxonomic divergence among the species of ferns. A Pearson's correlation coefficient was computed, based on average tracheid lengths from 221 species of ferns, and a divergence index based on 8 characters accepted as indicators of specialization or primitiveness in the ferns. A statistically significant correlation (at the 5% level) between length and divergence was found for root tracheids, but not for rhizome or petiolar tracheids. A better understanding of fern evolution is necessary before a more precise picture of length correlation and divergence in the ferns can be obtained.
INITIAL VASCULARIZATION OF THE VEGETATIVE SHOOT OF ABIES CONCOLOR
Authors: Parke Robert V.
Published: January 2018

Parke, Robert V. (Colorado State U., Fort Collins.) Initial vascularization of the vegetative shoot, of Abies concolor. Amer. Jour. Bot. 50(5): 464–469. Illus. 1963.—In the dormant winter bud, the future vascular system of the shoot exists as a rather ill‐defined system of procambial strands, which extends acropetally from the scale traces through a plate of thick‐walled, deeply staining cells, the crown, and into the axis and the numerous foliar primordia making up the telescoped shoot. Each foliar primordium receives a single procambial strand or leaf trace. The procambial strands differentiate acropetally. No differentiated vascular tissue was observed in the dormant shoot. As the shoot elongates in the spring, vascular differentiation progresses at a rapid rate. In the leaf traces, protophloem differentiates acropetally. The protoxylem, which appears first in the axial region of the trace, differentiates acropetally into the foliar primordium and basipetally into the stem. The first‐formed phloem elements are short‐lived. They are nucleate and without sieve areas. In the protoxylem, the first‐formed tracheids are mostly of the annular or spiral‐thickened type.
CALAMOCARPON INSIGNIS, A NEW GENUS OF HETEROSPOROUS, PETRIFIED CALAMITEAN CONES FROM THE AMERICAN CARBONIFEROUS
Authors: Baxter Robert W.
Published: January 2018

Baxter, R. W. (U. Kansas, Lawrence.) Calamocarpon insignis, a new genus of heterosporous, petrified calamitean cones from the American Carboniferous. Amer. Jour. Bot. 50(5): 469–476. Illus. 1963.—Calamocarpon insignis is described as a new genus of calamitean cone based on numerous fragments of microsporangiate and megasporangiate cones found in coal balls of middle Pennsylvanian age from the Cherokee Group of Kansas and the Des Moines Series of Iowa. The cones are similar to Calamostachys in general construction, having a hollow pith, prominent protoxylem canals, and alternating whorls of sterile bracts and sporangiophores. They differ in that the microsporangiate cones bear microsporangia each containing several hundred microspores which may occur as tetrads or single spores, while the megasporangiate cones bear large rectangular megasporangia each containing a single functional megaspore surrounded by sterile nutritive tissue. The microspores average 30–40μ in diameter compared to a maximum measurement of 2.7 × 0.7 mm for the single rectangular megaspore. The female gametophyte was produced within the megaspore which was held within the megasporangium during the entire period of development. The megasporangia were deciduous so that the entire structure was shed as a unit.
CONTRIBUTIONS TO OUR KNOWLEDGE OF AMBROSIA FUNGI. II. ENDOMYCOPSIS FASCICULATA NOM. NOV. (ASCOMYCETES)
Authors: Batra Lekh R.
Published: January 2018

Hatha, Lekh R. (U. Kansas, Lawrence.) Contributions to our knowledge of ambrosia fungi. II. Endomycopsis fasciculat nom. nov. (Ascomycetes). Amer. Jour. Bot. 50(5): 481–487. Illus. 1963.—Endomyceu bispora Verrall (1943) is a later homonym of E. bisporus Beck (1922) (= Endomycopsis bispora [Beck] Dekker), and the former is now described under the new name Endomycopsis fasciculata Batra. The ambrosia beetle Gnathotrichus materiarius (Fitch) lives symbiotically with Endomycopsis fasciculata which serves as the major source of food for the larvae and probably for the adults. The fungus forms an extensive palisade lining throughout the larval or pupal cells and the main tunnel dug by the mother. All stages of the fungus can be obtained from the same tunnel and the fungus seems to be homothallic. The asci are typically 2‐spored and aseosporcs are eucullate. The fungus does not assimilate nitrate as the sole source of nitrogen. Detailed morphology and nutritional requirements of E. fasciculata are discussed.
RAGWEED POLLEN DENSITY
Authors: Harrington James B. , Metzger Kurt
Published: January 2018

Harrington, James B., Jr., and Kurt Metzger. (U. Michigan, Ann Arbor.) Ragweed pollen densitv. Amor. Jour. Bot. 50(6) : 532–539. Illus. 1963.—The density of ragweed pollen has been measured using a Beckman gas pyenometer. Commercially dried pollen of Ambrosia artemisiifolia in moisture equilibrium with air at 52% relative humidity had an effective density2 of 0.84 g/cc, while the density of the solid material in the grain was 1.32 g/cc. The density of fresh ragweed pollen varies with age and relative humidity, being 1.28 g/cc at 100% humidity and 1.05 g/cc at humidities below 52%. After dehiscence, the evaporation of water from the pollen grain is extremely rapid so that adjustment to the external humidity regime is virtually instantaneous.
ONTOGENY AND STRUCTURE OF THE SECONDARY PHLOEM IN PYRUS MALUS
Authors: Evert Ray Franklin
Published: January 2018

Evert, Ray F. (U. Wisconsin, Madison.) Ontogeny and structure of the secondary phloem in Pyrus malus. Amer. Jour. Bot. 50(1): 8–37. Illus. 1963.—The secondary phloem of apple consists of sieve‐tube elements, companion cells, phloem parenchyma cells, fiber‐sclereids, and ray parenchyma cells. The sieve‐tube elements are generally long, slender cells with very oblique end walls and much‐compounded sieve plates. All sieve‐tube elements initially possess nacreous thickenings. Similar wall thickenings were observed in the differentiating fiber‐sclereids and xylem elements. Of the 245 sieve‐tube elements critically examined, 242 were associated with companion cells. All of the companion cells were shorter than their associated sieve‐tube elements. Young companion cells possess slime bodies which later become dispersed. Callose is often found on the sieve‐tube element side of the common wall between sieve‐tube element and companion cell. In several collections, callose was found on both sides of that wall. The parenchyma cells are of 3 types: crystal‐containing cells; tannin‐and/or starch‐containing cells; and those with little or no tannins or starch. Any type parenchyma cell may be on to genetically related to a sieve‐tube element, that is, may be derived from the same phloem initial as the sieve‐tube element. Morphologically, the phloem parenchyma cells intergrade with the companion cells, the tannin‐ and starch‐free parenchyma cells often being difficult to distinguish from companion cells. Most of the tannin‐ and starch‐free parenchyma cells collapse when the contiguous sieve‐tube elements become nonfunctional. The fiber‐sclereids arise from parenchyma cells which overwinter on the margin of the cambial zone and differentiate in nonfunctional phloem.
THE ONTOGENY OF THE APOTHECIA OF PYRONEMA DOMESTICUM
Authors: Moore Elizabeth J.
Published: January 2018

Moore, Elizabeth J. (Cornell U., Ithaca, N. Y.) The ontogeny of the apothecia of Pyronema domesticum. Amer. Jour. Bot. 50(1) : 37–44. Illus. 1963.—A single hyphal strand produces a cluster of antheridia and ascogonia, each pair of like or unlike sexual differentiation. Each cluster forms 1 apothecium. Plasmogamy is followed by nuclear migration from the antheridium, and an ascogenous system develops from each ascogonium. Concurrently, a sterile system of hyphae arises from the stalk cells supporting the ascogonia and antheridia. Apothecial expansion occurs as a result of the continuous proliferation of all structural elements. Comparisons are made with the closely related and easily confused P. omphalodes (= P. confluens).
INVESTIGATIONS OF NORTH AMERICAN CYCADEOIDS: CONES OF CYCADEOIDEA
Authors: Delevoryas Theodore
Published: January 2018

Delevoeyas, Theodore. (Yale U., New Haven, Conn.) Investigations of North American cycadeoids: cones of Cycadeoidea. Amer. Jour. Bot. 50(1): 45–52. Illus. 1963.—A reinvestigation of the morphology of cones of Cycadeoidea indicates that they did not expand into flower‐like structures at maturity The microsporangiate region was actually a compound synangium fused peripherally and, for at least part of the time, along the inner surface surrounding the ovulate receptacle. Capping the microsporangiate region is a massive parenchymatous dome. Synangia were borne along trabecular structures which connected the outer part of the microsporangiate structure to the inner face. Pollen may have been released after an abscission of the entire compound synangium.
SEASONAL TRENDS IN RATES OF PHOTOSYNTHESIS AND RESPIRATION OF LOBLOLLY PINE AND WHITE PINE SEEDLINGS
Authors: McGregor William H. Davis , Kramer Paul J.
Published: January 2018

McGregor, William H. Davis (Clemson Coll., Clemson, S.C.), and Paul J. Kramer. Seasonal trends in rates of photosynthesis and respiration of loblolly pine and white pine seedlings. Amer. Jour. Bot. 50(8): 760–765. Illus. 1963.—Seasonal trends in the rates of photosynthesis and respiration of potted loblolly and white pine seedlings were studied by measuring CO2 exchange with an infra‐red gas analyzer at intervals during a year. The seedlings were kept out‐of‐doors, but measurements were made indoors at 25 C and 4000 ft‐c of light. Beginning in February, the rate of photosynthesis per plant of both species increased, reaching a peak in mid‐September for loblolly pine and in mid‐July for white pine and then declining rapidly after mid‐September for both species. The spring increase began before new needles emerged and the autumn decline was not accompanied by appreciable loss of foliage. The respiration rate of loblolly pine increased steadily throughout the year. Respiration of white pine increased until mid‐May and then remained fairly constant through the remainder of the year. Maximum rate of photosynthesis per unit of fascicle length occurred in July for the white pine and in May for the loblolly pine, and rates declined after September in both species. Respiration rate per unit of fascicle length showed a marked increase as spring growth began in April, then decreased to a minimum in September and increased during the winter in both species. Total chlorophyll per seedling reached a maximum in September for both species and declined slightly during winter. Total chlorophyll per unit of fascicle length increased in the spring, declined slightly in midseason, and increased again in September. Photosynthesis per unit of chlorophyll reached a maximum in May for loblolly pine and in July for white pine. Stem elongation of white pine was 88% completed by May 15. On the same date, stem elongation of loblolly pine was only 42% completed.
COMPARATIVE CYTOHISTOLOGICAL STUDIES ON INHIBITION AND PROMOTION OF STEM GROWTH IN CHRYSANTHEMUM MORIFOLIUM
Authors: Sachs R. M. , Kofranek A. M.
Published: January 2018

Sachs, R. M. (U. California, Davis), and A. M. Kopranek. Comparative cytohistological studies on inhibition and promotion of stem growth in Chrysanthemum morifolium. Amer. Jour. Bot. 50(8): 772‐779. Illus. 1963.—The present study with Amo, CCC, and Phosfon,3 3 substances which inhibit stem elongation, shows that all inhibit subapical cell expansion and division in Chrysanthemum morifolium var. ‘Indianapolis Yellow.‘ Furthermore, GA,3 in preventing the inhibition of stem elongation, maintains subapical activity at normal or greater than normal levels. For comparative purposes concentrations of the retardants and GA have been selected which completely prevent or promote the maximum rate of stem elongation. Phosfon causes complete inhibition of root growth and almost completely prevents dry matter accumulation in the tops. However, GA does not prevent such deleterious effects. Thus, GA and the growth retardants are mutually antagonistic only with respect to stem elongation and not to other aspects of growth. Furthermore, none of the retardants inhibits transverse stem growth; on the contrary transverse cell expansion and division in the subapical tissues are stimulated by the retardants, and as a result the stems of such plants are thicker than normal. GA not only prevents the thickening effect of the retardants, but, at the doses applied, GA‐treated stems are considerably thinner than those of the controls, having fewer and smaller cells across the pith, cortical, and vascular tissues. Apparently, then, there is a relationship between longitudinal and transverse growth in the subapical tissues such that if one is promoted, the other is inhibited.
FLOWERING RESPONSES AND PHYLOGENY IN THE PHACELIA FRANKLINII GROUP (HYDROPHYLLACEAE)
Authors: Gillett George W.
Published: January 2018

Gillett, George W. (U. Hawaii, Honolulu.) Flowering responses and phylogeny in the Phacelia franklinii group (Hydrophyllaceae). Amer. Jour. Bot. 50(8): 798–801. Illus. 1963.—Phacelia franklinii is long‐day positive, with or without gibberellin, but P. sericea, P. idahoensis, P. mollis, and P. lyallii did not flower under these conditions. The latter 4 species flowered after short‐day, low‐temperature induction treatments. An interpretation of phylogenetic relationships, based on flowering responses, genetic compatibility, and morphological and anatomical information, is presented.
APOMIXIS AND POLYEMBRYONY IN HIEROCHLOË ODORATA
Authors: Norstog Knut
Published: January 2018

Norstog, Knut. (Wittenberg U., Springfield, Ohio.) Apomixis and polyembryony in Hierochloe odorata. Amer. Jour. Bot. 50(8): 815–821. Illus. 1963.—Hierochloë odorata from Michigan, having 2n = 56 chromosomes, was found to reproduce by pseudogamous fertilization of diploid aposporous embryo sacs. Diploid embryos, 2n= 56, and 5n = 140 ± endosperm occurred together. Megasporogenesis was incomplete, and aposporous embryo sac initials developed directly into 8‐nucleate Polygonum type embryo sacs. Microsporogenesis was irregular with univalent, bivalent and multivalent chromosomes in meiosis‐I. Dyads and microspores varied between n = 24 and n = 32, and less than 50% of the pollen grains stained with acetocarmine. Two other races of H. odorata are known to occur in North America. They are an apparently infertile type in Canada with 2n = 28, and a perfectly fertile race from coastal Connecticut also with 2n = 28. It is suggested that the H. odorata with 2n = 56 is a derivative of the sterile Canadian race.
ANALYSIS OF PETAL VENATION IN RANUNCULUS. I. ANASTOMOSES IN R. REPENS V. PLENIFLORUS
Authors: Arnott Howard J. , Tucker Shirley C.
Published: January 2018

Arnott, Howard J., and Shirley C. Tucker. (Northwestern U., Evanston, Ill.) Analysis of petal venation in Ranunculus. I. Anastomoses in R. repens v. pleniflorus. Amer. Jour. Bot. 50(8): 821–830. Illus. 1963.—The venation patterns of 1218 petals of Ranunculus repens v. pleniflorus were analyzed, with particular attention to the number and position of vein anastomoses. The essentially open dichotomous vascular pattern is complicated by the presence of vein fusions in 69.4% of the petals. The anastomosis ratio (number of anastomoses/number of appendages) is, therefore, high (1.37), compared to a maximal 0.61 for Ginkgo leaves. Of the petals having such fusions, 55.3% have more than 1 anastomosis; the maximal number of fusions found per petal is 8. The presence of anastomoses shows a high degree of correlation with petal size and petal lobing. The types of fusions (types A, B, C, D) are identical with those found in Ginkgo leaves, with the addition of 2 modifications of type C. Curiously, types C and D account for 98.7% of the total anastomoses, while types A and B are rare. An analysis of the location of each type within the petal shows that type C's are disproportionately numerous along the distal periphery, and that type‐D fusions are unusually numerous in the central and basal regions. Such evidence suggests that the occurrence of a vein fusion is no “accident,” but rather that it is one manifestation of morphogenetic control.
THE ROLE OF LIGHT IN HISTOGENESIS AND DIFFERENTIATION IN THE SHOOT OF PISUM SATIVUM. III. THE INTERNODE
Authors: Thomson Betty F. , Miller Pauline Monz
Published: January 2018

Thomson, Betty F., and Pauline Monz Miller. (Connecticut Coll., New London.) The role of light in histogenesis and differentiation in the shoot of Pisum sativum. III. The internode. Amer. Jour. Bot. 50(3): 219–227. Illus. 1963.—Seedlings of Pisum sativum were grown under constant conditions and exposed daily to red or white fluorescent light or kept in total darkness. Counts and measurements of internodal cells in both transverse and longitudinal directions show that light does not alter the sequence or pattern of tissue differentiation, including the sequence of xylem maturation within the vascular bundle. Light does accelerate the rate of a constant course of differentiation. Light advances the time of division and enlargement of cortex, xylem, phloem, and pith cells in the longitudinal direction but reduces both the final number and the final length attained in all cases. It is concluded that light accelerates all phases of shoot growth and differentiation and that cell division and elongation in the later phases of internodal growth are reduced by light because of accelerated cell maturation.
GROWTH OF EDIBLE CHLOROPHYLLOUS PLANT TISSUES IN VITRO
Authors: Hildebrandt A. C. , Wilmar J. C. , Johns H. , Riker A. J.
Published: January 2018

Hildebrandt, A. C, J. C. Wilmar, H. Johns, and A. J. Riker. (U. Wisconsin, Madison.) Growth of edible chlorophyllous plant tissues in vitro, Amer. Jour. Bot. 50(3): 248–254. Illus. 1963.—Plant callus cultures were attempted from roots, stems, leaves or excised embryos of 32 species of plants on a basal mineral salts–sucrose agar medium (T‐medium), on T‐medium + coconut milk + α‐naphthaleneacetic acid + calcium pantothenate (C‐medium) and on C‐medium + 2,4‐dichlorophenoxyacetic acid (D‐medium). Embryos on T‐ or C‐medium generally produced normal plants, while on D‐medium, they often produced callus only. Fresh isolates of carrot, endive, lettuce, parsley, red kidney bean, and navy bean gave moderate to excellent callus on C‐medium. Parsley and navy bean also produced excellent callus on D‐medium. Strains of callus from potato, tomato, grape and rose also grew well on C‐ or D‐medium. In the light, red pigmentation developed on rose, parsley, and grape callus. Chlorophyll formation was inhibited on D‐medium, but on C‐medium more or less chlorophyll was initiated in callus from carrot, endive, lettuce, pea, potato and certain rose varieties. Chlorophyll formation was also strong in endive callus on T‐medium supplemented with casein hydrolysate, i‐inositol and NAA. The amount and type of sugar used in C‐medium influenced the amount of growth and were critical in relation to chlorophyll formation. Carrot tissues in constant light produced abundant chlorophyll and were still growing on media without added sugar after 6 weeks.
ESTIMATION OF NUCLEAR RATIOS DIRECTLY FROM HETEROKARYOTIC MYCELIA IN SCHIZOPHYLLUM
Authors: Snider Philip J.
Published: January 2018

Snider, P. J. (U. California, Berkeley.) Estimation of nuclear ratios directly from heterokaryotic mycelia in Sehizophyllum. Amer. Jour. Bot. 50(3): 255–262. Illus. 1963.—The principles used to analyze nuclear ratios with macerated mycelium are similar in part to those of classic methods utilizing spore suspensions, but some distinctive features are evident in the present method. It is simple, adapted particularly for analyzing highly disparate ratios, and probably suitable for the simultaneous comparison of ratios in mycelium and spores. The technique can be combined with others, as described, to devise a test suggesting whether random or non‐random spatial distributions of nuclei exist in heterokaryons with disparate ratios. Direct analysis, as described and evaluated here, was used in a study reported in a companion paper, and numerous applications in fungi seem probable.
CYTOTAXONOMY OF TWELVE SPECIES OF HIBISCUS SECTION FURCARIA
Authors: Menzel Margaret Y. , Wilson F. D.
Published: January 2018

Menzel, Margaret Y. (Florida State U., Tallahassee), and F. D. Wilson. Cytotaxonomy of twelve species of Hibiscus section Furcaria. Amer. Jour. Bot. 50(3): 262–271. Illus. 1963.—Metaphase‐I chromosome numbers and pairing in 88 accessions showed that H. cannabinus, H. costatus, and H. surattensis are diploid (n = 18); and H. acetosella, H. aculeatus, H. bifurcatus, H.furcellatus, H. meeusei, H. radiatus, H. rostellatus and H. sabdariffa are tetraploid (n = 36), with similar low multivalent frequencies, hence probably allotetraploids each combining 2 well‐differentiated genomes. No intraspecific variation in ploidy was found. Fertile, vigorous F1 hybrids between H.furcellatus and H. bifurcatus showed complete chromosome pairing (n = 36), confirming a close relationship between the parents. Two African strains of H. diversifolius were octoploid (n = 72) with low multivalent frequency and hence probably contain 4 differentiated genomes. At least 4, perhaps 5 or 6, differentiated genome groups are represented in tropical Africa, and at least 2 in the American tropics.
ELECTRON MICROSCOPY OF THE VOLVOCACEAE AND ASTREPHOMENACEAE
Authors: Lang Norma J.
Published: January 2018

Lang, Norma J. (U. Texas, Austin.) Electron microscopy of the Volvocaceae and Astrephomenaceae. Amer. Jour. Bot. 50(3): 280‐300. Illus. 1963.—Clonal cultures of Gonium sociale, G. pectorale, Pandorina morum, Eudorina elegans, Eudorina sp., Volvulina steinii, V. pringsheimii, Platydorina caudata, Pleodorina illinoisensis, P. californica, Volvox aureus, V. tertius, V. globator, V. barberi, and Astrephomene gubernaculifera representing the Volvocaceae and Astrephomenaceae in the Volvocales were examined with the electron microscope and their ultrastructure compared. The ultrastructure of the various organelles is basically similar in the species studied and no increase in cellular complexity is found to accompany the evolutionary trends evidenced in the Volvocaceae. The ultrastructure of a colonial cell is basically that of Chlamydotnonas. A cytoplasmic membrane having a unit membrane structure encompasses a cell and is continuous with the double‐membraned flagellar sheaths. The flagella contain the typical 9 + 2 fibril arrangement with the 2 axial fibrils terminating in a cylinder at the flagellar base and the 9 peripheral pairs continuing into the cytoplasm as a basal body. The organelles comprising the cytoplasm are: mitochondria with plate‐like cristae; dictyosomes composed of stacks of agranular cisternae; small, rough or smooth‐surfaced vesicles; an endoplasmic reticulum of granule‐bearing and agranular tubules, lamellae and broad cisternae; vacuoles which are either contractile, contain fine granular and fibrillar material, or have dense contents probably representing polyphosphate; lipid bodies; and dense granules 100–150 A which have been called ribosomes. The finely granular nucleoplasm is surrounded by a porous, double‐membraned nuclear envelope and contains a centric nucleolus composed of dense, spherical granules. The outer membrane of the nuclear envelope bears granules and may have granular extensions into the perinuclear cytoplasm. Each extension appears to encompass one or several dictyosomes and has been termed an “amplexus.” The amplexi are agranular on the surface contiguous to a dictyosome. A double‐membraned chloroplast envelope is continuous around the single, cup‐shaped chloroplast. The basic chloroplast units are discs closed at each end, occurring in stacks of varying number parallel to the envelope. The presumed proteinaceous matrix of the basal pyrenoid is penetrated by elongated, tubular elements which connect with the lamellar discs. Multiple rows of granules, associated with individual discs, form the anterior stigma within the chloroplast envelope. The colonial matrix is not a structureless, mucilaginous material uniting the cells in colonies, but it has rather a highly complex structure especially around the periphery of the colony and the flagellar channels. The apparent substitution of a fibrillar layer of the colonial matrix for the discrete compact cell wall, such as is found in Chlamydomonas, implies a greater degree of complexity in the evolution of these colonial genera than is generally assumed.