bluuebunny/crossref_metadata_2025 huggingface dataset:
ONTOGENETIC AND HISTOCHEMICAL CHANGES IN THE VEGETATIVE SHOOT TIP OF CHENOPODIUM ALBUM
Authors: Gifford Ernest M. , Tepper Herbert B.
Published: January 2018

Gifford, Ernest M., Jr., and Herbert B. Tepper. (U. California, Davis.) Ontogenetic and histochemical changes in the vegetative shoot tip of Chenopodium album. Amer. Jour. Bot. 49(8): 902–911. Illus. 1962.—A distinct central zone is present in apices of young, rapidly growing seedlings of Chenopodium album. This zone is clearly evident when the plane of section includes developing leaf buttresses and/or newly formed leaf primordia, but is not visible if the cells associated with these developing foliar organs are not in the plane of section. Cells in the central zone contain markedly lower concentrations of RNA than those of the peripheral zone. Differences in DNA, SH‐protein, total protein, and histone concentration of cells in the apex parallel the zonal distribution of RNA, but are much less obvious. As the plant ages and the rate of leaf production decreases, the zonal distribution of the above‐mentioned compounds becomes less and less obvious. Cells at sites of leaf initiation in older seedlings still have slightly higher RNA concentrations, but a central zone such as is visible in the young seedlings is no longer evident. The axial tunica cells do, however, contain noticeably lower DNA and histone concentrations than the remaining cells of the shoot apex. Changes occur in the size of nucleoli during ontogeny and the possible relationship between nucleolar size and modifying factors is discussed.
ANEUSOMATY IN ANEUPLOID POPULATIONS OF CLAYTONIA VIRGINICA
Authors: Lewis Walter H.
Published: January 2018

Lewis Walter H. (Stephen F. Austin State Coll., Nacogdoches, Texas.) Aneusomaty in aneuploid populations of Claytonia virginica. Amer. Jour. Bot. 49(9): 918–928. Illus. 1962.—From 2 central east Texas populations of Claytonia virginica, 15 chromosome numbers, 2n = 14, 15, 16, 18, 25, 26, 27, 28, 29 30, 31, 32, 33, 36, and 58, were found among a sample of 181 plants. The most frequently encountered numbers were 2n = 14, 28, and 29. Among an additional 14 plants the pollen mother cells in the same bud differed from one another in chromosome number, as well as the pollen and premeiotic cells from the same plant. The chromosomes of the most unstable plant varied from 2n = 14–36. Numerous meiotic abnormalities, including inversions, dicentrics, bridges, fragments, non‐disjunctions, univalents, and multivalents, were observed for the aneusomatic and trisomic plants. It is suggested that the origin of the aneusomatics is related to the numerical disparity of the gametic chromosomes composing them. Since the species is perennial in habit, thereby allowing the unstable plants to produce gametes with varying chromosome numbers year after year, it is further proposed that the wide range of aneuploid known for C. virginica resulted, at least in part from the presence of aneusomatic individuals.
CELL WALL SYNTHESIS AND CELL ELONGATION IN OAT COLEOPTILE TISSUE
Authors: Ray Peter M.
Published: January 2018

Ray, Peter M. (U. Michigan, Ann Arbor.) Cell wall synthesis and cell elongation in oat coleoptile tissue. Amer. Jour. Bot. 49(9): 928–939. Illus. 1962.—Cell wall synthesis in oat coleoptile cylinders tends to run parallel with but not usually proportional to cell elongation both under promotion by auxin and sugar and under inhibition by supraoptimal auxin or sugar, or by a variety of other inhibitors. Inhibitors of elongation fall into 2 classes with respect to their effects on wall synthesis: (1) those which inhibit the 2 processes approximately equally (galactose, mannose, mannitol, azide, iodoacetate, dinitrophenol, low temperature, supraoptimal auxin) and (2) those which inhibit elongation percentagewise much more strongly than wall synthesis, so that as complete inhibition of elongation is approached, substantial wall synthesis continues (Ca+ +, fluoride, arsenite, mercurials). When coleoptile cylinders elongate in the absence of sugar, the cell walls appear to become markedly thinner, and in some experiments negligible increase in total wall material apparently occurs. However, the amount of α‐cellulose does rise. Increase in cell wall material occurs during elongation of cylinders at 2 C. The results are interpreted as indicating that during elongation the bulk of new cell wall material is added by apposition, but a certain proportion of the new material is probably introduced within the existing wall structure and induces its expansion.
BIOSYSTEMATIC INVESTIGATIONS IN THE GENUS AGROPYRON. I. CYTOLOGICAL STUDIES OF SPECIES KARYOTYPES
Authors: Schulz‐Schaepper Jurgen , Jurasits Peter
Published: January 2018

Schulz‐Schaeffer, Jurgen (Montana State Coll., Bozeman), and Peter Jurasits. Biosystematic investigations in the genus Agropyron. I. Cytological studies of species karyotypes. Amer. Jour. Bot. 49(9): 940–953. Illus. 1962.—Twenty‐five species of the genus Agropyron are analyzed cytologically in this presentation. Accession numbers, names of collectors, locations where seed was collected, and observed chromosome numbers are listed. Chromosome numbers of A. panormitanum (2n = 28), A. lolioides (2n = 58), A. brachyphyllum (2n = 42), A. ciliatiflorum (2n = 28), A. kosanini (2n = 56), A. pseudorepens (2n = 28), A. squamosum (2n = 42), and A. subulatum (2n = 56) are reported. No previous counts in these species are known to the authors. Chromosome counts of A. caespitosum (2n = 42) and A. elongatiforme (2n = 58), deviate from previous reports. Idiograms of all species and photomicrographs of mitotic metaphase root tip cells of 14 species are presented. The distribution of 11 satellite‐chromosome types in 25 Agropyron species is shown in Table 2. The proportions of these 11 satellite‐chromosome types are recorded in Table 3. The significance of these satellite chromosomes as indicator chromosomes for genome relationships is discussed together with the pertinent literature.
OBSERVATIONS ON THE ONTOGENY OF LEPIDOCARPON
Authors: Balbach Margaret Kain
Published: January 2018

Balbach, Margaret Kain. (U. Illinois, Urbana.) Observations on the ontogeny of Lepidocarpon. Amer. Jour. Bot. 49(9): 984–989. Illus. 1962.—This paper is a description of an apical fragment of a petrified Lepidocarpon cone of middle‐Pennsylvanian age from Illinois. Prior to the discovery of this cone, no evidence was available as to the origin of the lateral laminae (“integuments” of Scott, 1901) which enclose the megasporangium. This cone apex, however, shows very young sporangia in successive stages of development and the laminae can be seen to arise from the lateral margins of the pedicel at an early stage in ontogeny. The laminae are present to a recognizable degree even in the youngest sporangia in the upper levels of the cone. Sporangia in the successively lower levels show a progressive envelopment by the laminae; growth of the latter appears to have been synchronous with that of the sporangium. This finding warrants an emendation of that part of the original diagnosis of the genus (Scott, 1901) which describes the immature stage as lacking the lateral laminae. The suggestion also is made that those unintegumented forms included by Scott in the taxon Lepidocarpon lomaxi may actually have been monosporate, megasporangiate, lepidostroboid sporophylls, and, hence, they should be considered to be a separate taxon.
CYTOLOGICAL STUDIES OF NONTRUE–BREEDING MUTANTS IN SORGHUM OBTAINED AFTER COLCHICINE TREATMENT
Authors: Sanders Mary E. , Franzke Clifford J.
Published: January 2018

Sanders, Mary E., and Clifford J. Franzke. (South Dakota State Coll.. Brookings.) Cytological studies of nontrue‐breeding mutants in sorghum obtained after colchicine treatment. Amer. Jour. Bot. 49(9): 990–996. Illus. 1962.—Although pollen mother cells of nontrue‐breeding mutant plants obtained after colchicine treatment of sorghum seedlings, line ‘Experimental 3,’ showed normal chromosome behavior (10 bivalents) at phases of meiosis I, some abnormalities were found at corresponding stages in first‐ and second‐generation self‐progeny plants of some of them. The most frequent chromosome irregularities were an increase over ‘Experimental 3’ in number of cells containing univalents, and mixoploid tissues with tetraploid and diploid cells. The higher polyploid groups (6n, 8n, 10n) also present in 2 plants might be related to their male‐sterile condition rather than being an indication of the chromosome complement. Abnormalities in progenies suggest that some of the mutants might have been chimeras in which abnormalities were missed and raise the question whether chromosome changes are involved in the formation of the mutants in spite of the preponderance of normal diploid cells with 10 bivalents during prophase and metaphase of meiosis I. This could occur if sorghum contains a genetic mechanism which promotes bivalent rather than multivalent pairing. That such might be a possibility is indicated by the large numbers of bivalents and small numbers of multivalents found in polyploid cells or groups.
THE EFFECTS OF TRITIATED THYMIDINE INCORPORATION ON SECONDARY ROOT PRODUCTION BY PISUM SATIVUM
Authors: Hummon Margaret R.
Published: January 2018

Hummon, Margaret R. (Montana State U., Missoula.) The effects of tritiated thymidine incorporation on secondary root production by Pisum sativum. Amer. Jour. Bot. 49(10): 1038–1046. Illus. 1962.—Most studies of effects of radiation on plants have involved a general exposure of all the cells and tissues of an organ or entire plant. Tritiated thymidine offers a tool for selective irradiation of the nucleus with little effect on the cytoplasm of a cell. Furthermore, differential incorporation due to variation in the pattern of DNA synthesis permits selective irradiation of cells and tissues. In this study, developing primary roots of Pisum sativum were submerged for brief periods in a solution of tritiated thymidine. This resulted in an alteration of the lateral root pattern. In the area corresponding to the region of elongation during treatment, subsequent lateral root production was suppressed. This correlated with the portion of the root in which there was incorporation of tritiated thymidine into a high percentage of pericycle nuclei. Abnormal development of vascular tissues also occurred, with evidence of altered polarity in the xylem. Although incorporation also occurred in the apical meristem, the latter was not affected at this level of exposure. Thus, differential sensitivity as well as differential incorporation may have been involved in producing the temporary alteration of lateral root production.
RECOVERY OF NATIVE AND APPLIED AUXIN FROM THE LIGHT‐GROWN ‘ALASKA’ PEA SEEDLING
Authors: Scott Tom K. , Briggs Winslow R.
Published: January 2018

Scott, Tom K., and Winslow R. Briggs. (Stanford U., Stanford, Calif.) Recovery of native and applied auxin from the light‐grown ‘Alaska’ pea seedling. Amer. Jour. Bot. 49(10): 1056–1063. Illus. 1962.—The physiological status of both endogenous and exogenously applied auxin was compared in the epicotyl of the 9‐day‐old light‐grown ‘Alaska’ pea (Pisum sativum L.) by means of agar‐diffusion and short‐term ether extraction. A detailed analysis of endogenous auxin revealed a linear basipetal decrease in diffusible auxin within the growing region. A decrease in extractable auxin occurred only within the most mature region. The capacity for uptake of indole‐3‐acetic acid (IAA), applied in lanolin paste, was compared in different regions of the epicotyl. The fifth and most apical internode had the greatest capacity for uptake as measured by extraction. A reduced capacity was found in more basal internodes. The transport rate of applied IAA, under conditions of optimal uptake, was 10–12 mm/hr. An application of IAA for 24 hr resulted in a dramatic increase in auxin content throughout the length of the epicotyl compared to that found in the normal control. There was no apparent gradation in content from apex to base. An increase of diffusible auxin was also found, but only in the fourth and third internodes. That no such increase was detected in the basal 3 internodes suggested that the auxin transport system within this region had special properties related to a transition between shoot and root vascular patterns.
DISTRIBUTION OF ALLAGOCHROME IN VASCULAR PLANTS
Authors: Garrick Linda S. , Habermann Helen M.
Published: January 2018

Garrick, L. S., and H. M. Habermann. (Goucher Coll., Baltimore, Md.) Distribution of allagochrome in vascular plants. Amer. Jour. Bot. 49(10): 1078–1088. Illus. 1962.—Allagochrome is a blue‐green, water‐soluble pigment which can be reduced with a change in color to yellow and is autoxidizable in the presence of molecular oxygen. The development of quantitative procedures for assay has made possible an intensive study of its distribution in a wide variety of plant materials. The survey of 124 species representing 112 genera summarized in this paper indicates its presence in 55 of the species assayed. Quantitative estimates have been made of its concentrations in species showing positive tests. The widespread occurrence of allagochrome in vascular plants suggests a common function or accumulation as a metabolic product. The significance of variation in the position of absorption peaks, correlation of occurrence with known cases of cyanide‐resistant respiration, and species specificity of the chemistry of allagochrome are discussed.
WOOD OF GINKGO IN THE TERTIARY OF WESTERN NORTH AMERICA
Authors: Scott Richard A. , Barghoorn Elso S. , Prakash Uttam
Published: January 2018

Scott, R. A., E. S. Barghoorn, and U. Prakash. (U.S. Geol. Sur., Denver, Colo.) Wood of Ginkgo in the Tertiary of western North America. Amer. Jour. Bot. 49(10): 1095–1101. Illus. 1962. —Woods of Ginkgo and extinct related genera are very rare in the fossil record in contrast to the numerous ginkgoalean leaves. Ginkgo wood may be distinguished from other gymnosperms by a combination of anatomical features herein described. Ginkgo wood from beds of Miocene age at Vantage, Washington, first identified by Beck, is assigned to a new species, G. beckii. Ginkgo wood from the upper Eocene Clarno Formation, John Day Basin, Oregon, is described as G. bonesii sp. nov. Scarcity of fossil ginkgoalean woods may reflect unusual susceptibility to degradation of their cell walls in contrast to the greater chemical resistance to degradation which features many coniferous woods.
THE ESSENTIAL ROLE OF CALCIUM ION IN POLLEN GERMINATION AND POLLEN TUBE GROWTH
Authors: Brewbaker James L. , Kwack Beyoung H.
Published: January 2018

Brewbaker, James L., and Beyoung H. Kwack. (U. Hawaii, Honolulu.) The essential role of calcium ion in pollen germination and pollen tube growth. Amer. Jour. Bot. 50(9): 859–865. Illus. 1963.—A pollen population effect occurs whenever pollen grains are grown in vitro. Small pollen populations germinate and grow poorly if at all, under conditions which support excellent growth of large pollen populations. The pollen population effect is overcome completely by a growth factor obtained in water extracts of many plant tissues. This factor is shown to be the calcium ion, and its action confirmed in 86 species representing 39 plant families. Other ions (K+, Mg++, Na+) serve in supporting roles to the uptake or binding of calcium. The high requirement of calcium (300–5000 ppm, as Ca (NO3)2·4H2O, for optimum growth) and low calcium content of most pollen may conspire to give calcium a governing role in the growth of pollen tubes both in vitro and in situ. It is suspected that ramifications of this role extend to the self‐incompatibilities of plants and to the curious types of arrested tube growth distinguishing, for example, the orchids. A culture medium which proved its merit in a wide variety of pollen growth studies included, in distilled water, 10% sucrose, 100 ppm H3BO3, 300 ppm Ca (NO3)2·4H2O, 200 ppm MgSO4·7H2O and 100 ppm KNO3.
SYSTEMATIC REVISION OF THE SUCKER CREEK AND TROUT CREEK MIOCENE FLORAS OF SOUTHEASTERN OREGON
Authors: Graham Alan
Published: January 2018

Graham, Alan. (U. Michigan, Ann Arbor.) Systematic revision of the Sucker Creek and Trout Creek Miocene floras of southeastern Oregon. Amer. Jour. Bot. 50(9): 921–936. Ilus. 1963.—The Sucker Creek flora is preserved in shales of volcanic origin exposed in Malheur County, southeastern Oregon. A study of the flora has been made and the systematic revisions presented. The following new species are described: Osmunda claytonites, Davallia solidités, Shepherdia argen∗∗∗teaites, Magnolia ovulata, Anoda suckerensis, and Platanus youngii. A new combination, Hiraea knowltoni (Berry), is proposed. Additional synonymies, Incertae Sedis, and other taxonomic changes are included. The Trout Creek flora is to the west of Sucker Creek in Harney County, southeastern Oregon. The fossils are preserved in diatomite. Four new species are described: Equisetum miocenicum, Gossypium arnoldii, Urena miocenica, and Spiraea miocenica. New combinations are Pteridium calabazensis (Dorf), and Nymphaea rotunda (Arnold). A revised species list is given for the 2 floras. The Sucker Creek flora contains 47 families, 60 genera, and 69 species, presently identified. The Trout Creek flora contains 29 families, 51 genera, and 75 species. The distributional, ecologic, and geologic interpretations of the 2 floras will be presented in a subsequent publication.
NONESSENTIALITY OF CONCURRENT CELL DIVISIONS FOR DEGREE OF POLARIZATION OF LEAF GROWTH. II. EVIDENCE FROM UNTREATED PLANTS AND FROM CHEMICALLY INDUCED CHANGES OF THE DEGREE OF POLARIZATION
Authors: Haber Alan H. , Foard Donald E.
Published: January 2018

Haber, Alan H., and D. E. Foard. (Oak Ridge Natl. Lab., Oak Ridge, Tenn.) Nonessentiality of concurrent cell divisions for degree of polarization of leaf growth. II. Evidence from untreated plants and from chemically induced changes of the degree of polarization. Amer. Jour. Bot. 50(9): 937–944. Illus. 1963.—Tobacco leaves grow with a constant degree of polarization (i.e., ratio of rate of increase in length per mm length to rate of increase in width per mm width). During this growth there is decreasing mitotic activity. Data from the literature, including Sinnott's classic studies with cucurbit fruits, provide additional specific examples of growth of (1) constant degree of polarization during which (2) mitotic activity falls. The generalization that cell division plays no role in maintaining a constant degree of polarization is suggested by the widespread occurrence of these 2 features of growth in determinate organs. These considerations are consistent with our earlier finding that the degree of polarization of growth of the first foliage leaf of wheat is the same in seedlings normally growing with oriented cell divisions and in gamma‐plantlets, which are seedlings growing without cell division owing to gamma‐irradiation of the grain before sowing. The present work shows that the degree of polarization can be significantly increased by treatment with gibberellic acid and decreased by colchicine, even though it is unaffected by radiation‐induced mitotic inhibition. These chemically induced changes in the degree of polarization are, moreover, the same in unirradiated and in gamma‐plantlet leaves. We conclude that cell division is essential neither for maintaining the degree of polarization nor for changing the degree of polarization. These considerations lead to 3 biological conclusions, each of which is in harmony with simple geometric considerations: (1) cell divisions do not directly contribute to or cause growth; (2) cell division plays an essential and immediate role in influencing cell forms, but plays a secondary and much less important role in influencing organ form; and (3) there is a fallacy in the usual and accepted manner of interpreting changes in organ size as being due to changes in cell size and changes in cell number.
SOME LABOULBENIACEAE (ASCOMYCETES) ON INSECTS FROM INDIA AND INDONESIA
Authors: Batra Suzanne W. Tubby
Published: January 2018

Batra, Suzanne W. T. (U. Kansas, Lawrence.) Some Laboulbeniaceac (Ascomycetes) on insects from India and Indonesia. Amer. Jour. Bot. 50 (10): 986–992. Illus. 1963.—Laboulbenia camponoti, L. olitskyi, L. styphlomeri and Stigmatomyces scatellae are described as new. Developmental stages of the monoecious species, L. camponoti, on ants are illustrated. It appears to be closely related to the dioecious species, L. formicarum. New host and locality records are given for L. vulgaris, L. flagellata and S. hylemyiae.
A GLOSSOPTERIS FLORA FROM THE OHIO RANGE, ANTARCTICA
Authors: Cridland Arthur A.
Published: January 2018

Cridland, Arthur A. (Ohio State U., Columbus.) A Glossopteris flora from the Ohio Range, Antarctica. Amer. Jour. Bot. 50(2): 186–195. Illus. 1963.—Leaves of Glossopteris indica are the commonest fossils in the Mount Glossopteris Formation on Mount Schopf. Other fossils present are: Glossopteris ampla, G. anguslifolia, G. damudica, G. browniana, detached scales, sporangia of Arberiella containing bisaccate pollen grains, seeds of Samaropsis (principally S. longii), and some obscure fossils. These remains, and associated animal fossils, suggest that the Mount Glossopteris Formation is Permian. The plants evidently grew in a seasonal but favorable climate. These growth conditions indirectly support paleomagnetic calculations which indicate that in Late Permian time, Mount Schopf lay near latitude 50°S.
SOME OBSERVATIONS ON DNA CONTENT AND CELL AND NUCLEAR VOLUME GROWTH IN THE DEVELOPING XYLEM CELLS OF CERTAIN HIGHER PLANTS
Authors: List Albert
Published: January 2018

List, Albert, Jr. (Douglass Coll., Rutgers U., New Brunswick, N. J.) Some observations on DNA content and cell and nuclear volume growth in the developing xylem cells of certain higher plants. Amer. Jour. Bot. 50(4): 320–329. Illus. 1963.—The developing metaxylem cells of Acorus calamus roots undergo an over‐all growth in cell and nuclear volume that may be expressed roughly as a constant ratio of relative growth rates. Within this over‐all growth picture, however, there is a periodicity of both nuclear and cell volume growth. Other plants such as Peltandra, Eleocharis, and Dennstaedtia undergo a similar volume growth. Marsilea tracheary elements have an increase in nuclear number per cell by simultaneous divisions. Arisaema metaxylem nuclei go through a series of DNA doublings correlated with nuclear volume doubling and cell volume increase, at least up to the 16‐ or 32‐ploid level. The cells display some tendency to fall into size classes, expressing a pulsation in growth. A fluctuating alternation or stepwise growth of cell and nucleus appears to describe the data more suitably than the allometric growth equation. In Zea, the cell and nuclear volumes for metaxylem cells fit a fluctuating envelope better than the straight line, and there is again the probability that cell volumes fall into size classes related to nuclear volume class. The DNA content of the nuclei was determined to fall into a frequency distribution having peaks at the 4‐, 8‐, 16‐, and 32‐ploid equivalent, agreeing with an earlier report for diploid maize. DNA content was highly correlated with nuclear volume in the over‐all growth of the metaxylem cells.
STUDIES ON THE GIANT KELP, MACROCYSTIS. I. GROWTH OF YOUNG PLANTS
Authors: Neushul M. , Haxo F. T.
Published: January 2018

Neushul, M., and F. T. Haxo. (Scripps Inst. Oceanography, La Jolla, Calif.) Studies on the giant kelp, Macrocystis. I. Growth of young plants. Amer. Jour. Bot. 50(4): 349–353. Illus. 1963.—The growth of entire young plants of Macrocystis pyrifera was studied in the sea and in the laboratory. Measurements were made of plants in natural stands and of plants transplanted to submerged rafts. Macrocystis was raised in laboratory tanks under controlled conditions of light and temperature. Maximum growth rates in the laboratory paralleled those observed in the sea, plants doubling in area every 16–20 days and in length every 20–30 days under optimum conditions. The transplantation experiments and diving observations demonstrated the important influence of biological activity on the establishment and growth of young plants in the sea.
OSMOTIC ADJUSTMENT OF PLANTS TO SALINE MEDIA. II. DYNAMIC PHASE
Authors: Bernstein Leon
Published: January 2018

Bernstein, Leon. (U. S. Salinity Lab., Riverside, Calif.) Osmotic adjustment of plants to saline media. II. Dynamic phase. Amer. Jour. Bot. 50(4): 360–370. Illus. 1963.—The time‐course of osmotic adjustment in bean and pepper plants to increased salinity of the medium was determined by periodic sampling of plants following salt additions to the medium. Bean plants adjusted to increases of 1 atm OP within a day, the adjustment in roots occurring primarily at night following salt addition at 6 pm, whereas leaves and stems made most of their adjustment in the daytime. Pepper plants did not adjust completely to 1.5 atm NaCl additions in 48 hr, but OP increased by about the same amount in both species (0.5—1.0 atm per day). Diurnal fluctuations in OP of leaves and stems of both species and in roots of pepper were matched by parallel fluctuations in K concentrations. Added NaCl caused increased concentrations of K in leaves and stems which were more or less replaced by more slowly absorbed ions, Ca and Mg in bean leaves and Na in bean stems. Other salts produced comparable immediate effects on K level, but K was replaced more rapidly if the cation added was readily accumulated by the bean (Ca). In roots, Na uptake predominated if Na salts were added but K uptake was important on the CaCl2 treatment. The K effects suggest a passive distribution of K between the cell and the medium.
SHOOT TIP ABORTION IN ULMUS AMERICANA
Authors: Millington W. F.
Published: January 2018

Millington, W. F. (Marquette U., Milwaukee, Wis.) Shoot tip abortion in Ulmus americana. Amor. Jour. Bot. 50(4): 371–378. Illus. 1963.—Phenological observations of American elm have shown that the phenomenon of shoot tip abortion in which the distal several plastochrons of each shoot turn yellow and abort, inducing sympodial growth, occurs over a period of several weeks starting at the time fruits are shed from older trees. Time of abortion varies among plants of different age, among individuals of the same age, and among shoots on the same individual. In the latter case, time of abortion is inversely correlated with the vigor of the shoot, the most vigorous shoots on a branch being the last to abort. Abortion is first evident in the yellowing of the entire shoot tip. Cytohistological studies show that necrosis commences at the sixth to eighth node back of the apex, where it is apparent in autolysis of internal cells of the stipules. Necrosis progresses acropetally in the stipules and young leaves and ultimately involves the leaf primordia at the shoot apex. Mitosis ceases in the shoot apex and its meristematic appearance is lost. These changes follow in basipetal sequence in the axillary buds down to the bud below the abscission site. This bud remains active and will resume growth the following season. The abscission site is evident externally as a green‐yellow boundary in the basal part of the internode. No protective layer is present at the time of abscission, but it develops after the shoot tip abscises. There is no indication of blocking of vascular tissues before shoot tip abortion and limitation of water supply probably is not a causal factor. Photoperiod studies show that shoot tip abortion is accelerated in short days and delayed but not prevented in long days. Greenhouse experiments show that abortion is delayed also in seedlings, in plants supplied with organic fertilizer, or grown with the roots unconfined. Plants grown in a nutrient solution deficient in nitrogen aborted ahead of controls and plants deficient in calcium. Although shoot tip abortion occurs coincident with fruit drop, there is no indication of a causal relationship. The literature relating to shoot tip abortion is discussed in relation to the above observations.
PECTIN‐PROTEIN INTERACTION AS A BASIS FOR AUXIN‐INDUCED ALTERATION OF PROTEIN HEAT COAGULABILITY
Authors: Galston Arthur W. , Kaur Ravindar , Maheshwari Nirmala , Maheshwari Satish C.
Published: January 2018

Galston, Arthur W., Ravindar Kaur, Nirmala Maheshwari, and Satish C. Maheshwari. (Yale U., New Haven, Conn.) Pectin‐protein interaction as a basis for auxin‐induced alteration of protein heat coagulability. Amer. Jour. Bot. 50(5): 487–494. Illus. 1963.—The in vivo administration of 2,4‐D or other auxins to etiolated or green pea stem sections results in a decreased heat coagulability of the macromolecular components of the particle‐free cytoplasm of these tissues. Addition of auxin to homogenates is without effect. Gibberellins alone are also without effect, but may enhance the in vivo action of auxin. The altered heat coagulability may become apparent as soon as 4–6 hr after auxin administration, though longer induction periods are sometimes necessary. The auxin eff'ect is prevented by general metabolic inhibitors and most effectively by ethionine, whose inhibitory action is completely reversed by methionine. Electrophoresis on paper and on starch revealed no major differences between the proteins of control and auxin‐treated stems. Approximately 90% of the weight of the heat coagulum can be accounted for as protein; small quantities of nucleic acids, lipids, polysaccharides and pectins are also present. The “soluble pectin” content of the homogenate before heat coagulation is at least doubled by auxin treatment. This increase is also inhibited by ethionine, whoso effect is annulled by methionine. Addition of citrus pectin to control homogenates stabilizes the proteins against heat coagulation. It thus appears likely that the effect of auxin on the heat coagulability of the cytoplasmic proteins can be explained through effects on the metabolism of the materials which have been called “cold‐water‐soluble pectins.”
CYTOLOGY AND MORPHOLOGY OF A SYNTHETIC AGROPYRON TRICHOPHORUM × AGROPYRON DESERTORUM HYBRID
Authors: Dewey Douglas R.
Published: January 2018

Dewey, Douglas R. (Utah State U, Logan.) Cytology and morphology of a synthetic Agropyron trichophorum × Agropyron desertorum hybrid. Amer. Jour. Bot. 50(6): 552–562. Illus 1963.—A single hybrid was obtained from controlled pollinations of more than 1,200 emasculated florets of A. trichophorum (n=21) with A. desertorum (n = 14) pollen. Vegetative and spike characteristics of the hybrid were intermediate between those of the parent species. The A. desertorum parent behaved cytologically as an autotetraploid, whereas A. trichophorum was best described as a segmental autoallohexaploid. Chromosome associations at metaphase I in the 35‐chromosome hybrid averaged 5.75 I, 8.94 II, 2.91 III, 0.59 IV, and 0.04 V. On the basis of chromosome pairing in the parent species and their interspecific hybrid, it is suggested that A. trichophorum and A desertorum share 1 or 2 partially homologous genomes. A. desertorum and A. trichophorum were assigned genome formulas of AAAA and A1A1B1B1B2B2, respectively; and the hybrid genome formula was represented as AAA1B1B2.
GERMINATION‐REGULATING MECHANISMS IN CITRULLUS COLOCYNTHIS
Authors: Koller D. , Poljakoff‐Mayber A. , Berg A. , Diskin T.
Published: January 2018

Koller, D., A. Poljakoff‐Mayber, A. Berg, and T. Diskin. (Hebrew U., Jerusalem, Israel.) Germination‐regulating mechanisms in Citrullus colocynthis. Amer. Jour. Bot. 50(6): 597–603. Illus. 1963.—Intact seeds from mature, dry fruits of Citrullus colocynthis, collected in the southern Negev desert, did not germinate under a wide variety of experimental conditions. This inhibition was imposed by the testa, since germination was made possible by mechanically forcing open the testa, or by its complete removal. However, various pretreatments, including some which modified or even pierced the testa, failed to effect germination. No inhibitors were found in the testa and the manner in which it inhibits germination is yet unknown. How this inhibition is overcome in nature is also unknown. Germination of decoated seeds was inhibited by continuous light in combination with temperatures below 25 C. Removal of the inner seed membrane removed this inhibition, but, growth of the naked embryos at all temperatures was greatly reduced by continuous light, which also strongly influenced early development. An intact inner seed membrane had no effect on germination in darkness, but inhibited it in light at temperatures below 25 C. Inhibitory effects of the inner seed membrane could be duplicated by enclosing the naked embryos in moist filter paper and are thus probably the result of an interference with exchange of respiratory gases between the embryo and the atmosphere. Very low light intensities sufficed to inhibit decoated seeds, but at least 12‐hr daily illumination was required to produce significant inhibition. The blue region of the visible spectrum, transmitted by green and blue cellophane filters, was the most inhibitory. The site of light perception was located in the radicular portions of the embryo.
CUTICULAR ANALYSIS OF EOCENE LEAVES OF OCOTEA OBTUSIFOLIA
Authors: Dilcher David L.
Published: January 2018

Dilcheb, David L. (Yale U., New Haven, Conn.) Cuticular analysis of Eocene leaves of Ocotea obtusifolia. Amer. Jour. Bot. 50(1): 1–8. IIlus. 1963.—Several specimens of Ocotea obtusifolia collected from the Eocene clays at Puryear, Tennessee, were examined in detail. The megascopic and cuticular features of the leaves are described and their variations discussed. The lower epidermis was found to be less variable and a better tool to use in the cuticular analysis of this species than the upper epidermis. The cuticle of several genera and species of modern Lauraceae were also examined. Since none could be identified with the fossil cuticle, the designation Ocotea obtusifolia as based on megascopic characters is satisfactory.
MORPHOLOGY OF NEURONECTRIA PEZIZA
Authors: Hanlin Richard T.
Published: January 2018

Hanlin, Richabd T. (Georgia Expt. Sta., Experiment.) Morphology of Neuroneetria peziza. Amer. Jour. Bot. 60(1): 56–66. Illus. 1963.—Swollen tips of vegetative hyphae develop into multicellular, multinucleate ascogonia. Hyphae grow up to form a pseudoparenchymatous ascocarp wall. The ascogonia give rise to ascogenous cells from which croziers and asci form. As the ascocarp develops, an apical meristem produces many cells which are pushed downward and form a compact pseudoparenchyma in the centrum. As the asci form, the cells of the pseudoparenchyma elongate, forming central strands. These disintegrate as the asci grow up among them. Mature asci possess a thickened apical cap but no apical ring; the ascospores have longitudinal striations. The chromosome number is n = 5. The pattern of development resembles the Diapor the type of Luttrell but is unique in the formation of strands from the pseudoparenchyma. Other characters, however, indicate a closer affinity to Nectria.
KARYOTYPE ANALYSIS OF SOME SARCANTHINE ORCHIDS
Authors: Shindo K. , Kamemoto H.
Published: January 2018

Shindo, K., and H. Kamemoto. (U. Hawaii, Honolulu.) Karyotype analysis of some sarcanthine orchids. Amer. Jour. Bot. 50(1): 73–79. Illus. 1963.—Karyotypes were analyzed for 11 species in 10 genera of the sub‐tribe Sarcanthinae (Orchidaceae). These were Luisia teres, Vanda teres, Renanthera monachica, Arachnis flos‐aeris, Aerides odoralum, Vanda lamellata, Neofinetia falcata, Ascocenlruin curvifolium, Phalaenopsis sanderiana, Trichoglottis philippinensis and Angraecum eburneum. The chromosome number of all plants investigated was uniformly 2n = 38, but differences were observed for chromosome size and morphology. The chromosomes of Vanda teres and Luisia teres were among the largest and could be easily distinguished from those of Phalaenopsis sanderiana which were the smallest. Also, the karyotypes of Vanda teres and Luisia teres were the most asymmetrical with the greatest number of chromosomes with subterminal centromeres, while Trichoglottis philippinensis exhibited the most symmetrical karyotype. The significance of similarities and differences of karyotypes in relation to taxonomy and evolution in the Sarcanthinae was briefly discussed.
ANATOMY AND DEVELOPMENT OF THE FLOWER AND FRUIT OF PERESKIA PITITACHE
Authors: Boke Norman H.
Published: January 2018

Boke, Norman H. (U. Oklahoma, Norman.) Anatomy and development of the flower and fruit of Pereskia pititache. Amer. Jour. Bot. 50 (8): 843–858. Illus. 1963.—Flowers of P. pititache are about 6 cm in diameter and perigynous. The receptacle bears numerous broad bracts; the inner perianth segments are orange and deeply cleft; the numerous stamens develop centrifugally. The fundamentally superior gynoecium is broad and flat and consists of 10–18 connate carpels, the fertile portions of which are involute and adnate to the conical floral axis. The 8–16 ovules in each of the pocket‐like locules are borne in 2 rows along the zone of adnation; placentation is axile. The short style and the style branches are lined with stigmatic tissue, which extends downward among the ovules. There is no definite stigma. The tip of the floral axis retains its meristematic characteristics beyond anthesis. In early fruit development, the rim of the floral cup grows in height, while the residual floral axis becomes a conspicuous peg‐like columella. Concomitantly, the formation of numerous mucilage cells and cavities causes the ovary partitions and parts of the ovary roof to disintegrate. As a result, the seeds are contained in a single, moat‐like cavity, which appears inferior. Late fruit development is characterized by the differentiation of numerous fiber sclereids in association with the extensive and complex vascular system.
THE PHOTOINHIBITION OF GROWTH IN ETIOLATED STEM SEGMENTS. II. GROWTH CAUSED BY COBALT IN PISUM
Authors: Bertsch Walter F.
Published: January 2018

Bertsch, Walter F. (Yale U., New Haven, Conn.) The photoinhibition of growth in etiolated stem segments. II. Growth caused by cobalt in Pisum. Amer. Jour. Bot. 50(3): 213–219. Illus. 1963.—Etiolated pea stem sections were utilized to study the effects of various metal ions on the red, far‐red photoinhibition of stem growth. Excision of immature tissue results in loss of photosensitivity. All growth caused by cobalt, either in the presence or absence of sugar, was inhibited by brief exposure of the excised tissue to red light. Since growth caused by sugar is also light‐sensitive, it may be said that either cobalt or sugar may induce photosensitivity in this immature tissue. Other divalent metal ions were tested, but only nickel promoted growth. Although cobalt and nickel showed the same optimal concentration (ca. 2 × 10−5 m), growth caused by nickel was not photosensitive, suggesting that cobalt and nickel promoted growth through separate mechanisms. Since growth caused by indole‐3‐acetic acid or gibberellic acid is also insensitive to light in this tissue, a photosensitive sugar‐cobalt growth system has been experimentally separated from other growth‐controlling systems. The photoinhibition of a growth system which utilizes sugars and is promoted by cobalt and the relation of this system to certain de‐etiolation phenomena are discussed.
ON THE ORIGINS OF THE OVULE AND CUPULE IN LYGINOPTERID PTERIDOSPERMS
Authors: Camp Wendell H , Hubbard Mary M
Published: January 2018

Camp, Wendell H., and Mary M. Hubbard. (U. Connecticut, Storrs.) On the origins of the ovule and cupule in Lyginopterid pteridosperms. Amer. Jour. Bot. 50(3): 235–243. Illus. 1963.—The recently described Eurystoma angulare of the Lower Carboniferous with its naked, dichotomously branched, ovule‐bearing branch truss may be taken conceptually as a starting point in a series of evolutionary reductions and modifications involving other known forms which ultimately led to the cupule surrounding the solitary ovule of later lyginopterids. It is postulated that the integuments of these ovules also were derived from dichotomously branched lateral trusses which immediately subtended the primitive megasporangia, but of less complexity than that which produced the cupule. Eurystoma indicates that ovules evolved independently of leaves; therefore, ovules cannot be thought of as having been derived from leaf tissues. Evidence is presented indicating that, although these pteridosperms produced ovules of considerable complexity, they did not bear seeds but dropped the pollinated ovules before fertilization. The already specialized organization of the ovules of the Lower Carboníferous pteridosperms indicates that the group must have originated in the Devonian. The structure of the Lyginopterid ovule is reinterpreted, indicating a basic similarity to that of the angiospermous ovule.
DEVELOPMENT AND NUTRITION OF NEW SPECIES OF THRAUSTOCHYTRIUM
Authors: Goldstein Solomon
Published: January 2018

Goldstein, Solomon. (Brooklyn Coll., Brooklyn, N.Y.) Development and nutrition of new species of Thraustochytrium. Amer. Jcur. Bot. 50(3): 271‐279. Illus. 1963.—The life cycles of 2 lower Phycomycetes in sea‐water‐pollen culture are described and compared with variations observed in nutrient media. Some ecological implications are discussed. Both fungi are obligately marine and stenohaline. Maximal growth occurred with 2.5 and 3.0% NaCl not replaceable by KCl. However, omission of KCL from media resulted in reduced yields. Salinity optima were not temperature‐dependent and the organisms grew best at 12–25 C. Neither organism assimilated nitrogen in the form of KN03 or (NH4)2SO4. Optimal harvests were obtained with glutamate as the source of nitrogen and with carbon supplied as glucose, maltose, soluble starch, or cellobiose.
EFFECTS OF HELMINTHOSPORIUM VICTORIAE AND VICTORIN UPON PERMEABILITY
Authors: Wheeler Harry , Black Homer S.
Published: January 2018

Wheeler, Harry, and Homer S. Black. (Louisiana State U., Baton Rouge.) Effects of Helminthosporium victoriae and victorin upon permeability. Amer. Jour. Bot. 50(7): 686–693. Illus. 1963.—Helminthosporium victoriae, the causal agent of Victoria blight of oats, produces a potent toxin called victorin. All of the symptoms of Victoria blight, both visible and biochemical, can be induced in susceptible plants either by infection with H. victoriae or by treatment with victorin. Among the effects produced both by the fungus and the toxin are marked changes in respiration and cell permeability. These are of special interest because they are characteristic of many plant diseases. This paper is concerned with the nature of changes in permeability and the possible relation of these to changes in respiration observed in tissues infected with H. victoriae or treated with victorin. Suseeptible oat tissues treated with victorin lost electrolyes when suspended and shaken in distilled water more rapidly than control tissues, and the magnitude of the effect varied with the concentration of victorin applied. Similar results were obtained with naturally infected susceptible plants but not with inoculated or victorin‐treated resistant plants. The rate of electrolyte loss from victorin‐treated tissue had a low temperature coefficient typical of a physical process and was not dependent upon oxygen tension. The concentration of victorin needed to produce an increase in the rate of electrolyte loss was approximately 50‐fold less than that required to induce a significant increase in the respiratory rate. Changes in permeability were detected within 5 min after victorin was applied, whereas respiratory changes were not clearlyevident until after 30 min. These results indicate that if a causal relationship between these 2 phenomena exists, changes in permeability are responsible for changes in respiratory activity rather than vice versa.
A REVISION OF ARIOCARPUS (CACTACEAE). III. FORMAL TAXONOMY OF THE SUBGENUS ROSEOCACTUS
Authors: Anderson Edward F.
Published: January 2018

Anderson, Edward F. (Whitman Coll., Walla Walla, Wash.) A revision of Ariocarpus (Cactaceae). III. Formal taxonomy of the subgenus Roseocactus. Amer. Jour. Bot. 50(7): 724–732. Illus. 1963.—This is the first of 2 articles dealing with the formal taxonomy of Ariocarpus. The introduction contains sections on geographical distribution and habitat, policy of classification, and herbaria consulted. Acknowledgments are made to those who assisted in research or field studies. A description of the genus and a key to the subgenera and species is followed by a formal taxonomic treatment of the subgenus Roseocactus. This treatment includes a description, illustrations, a map of authenticated collection sites, citation of common names, a discussion of synonomy and types, and a list of specimens examined of each species and variety. The accepted species which are discussed are Ariocarpus kotschoubeyanus and A. fissuratus. The latter species consists of 2 varieties, var. fissuratus and var. lloydii.
PHENOTYPE DISTRIBUTIONS IN ASCI OF NEUROSPORA CRASSA
Authors: Mitchell Mary B.
Published: January 2018

Fourteen crosses are described from which 3103 asci were dissected and scored with respect to phenotype distribution patterns of 1, 2 or 3 markers. The results illustrate the following points. There may regularly occur preferred ratios, including 8:1, 4:1, 2:1 and 1:2, of first to second division segregation patterns. Variations in this ratio (designated here as S/C, meaning simple to complex phenotype distribution patterns), shown by the same marker in different crosses, may regularly be discontinuous in that the ratio may shift from one preferred value to another. Values of linkage‐correction factors applicable to certain crosses suggest that these factors also may constitute a discontinuous series. Control of phenotype distributions in asci by a systematic, but unknown, mechanism is thought to be suggested. Characteristics of the order of isolation of asci, from 2 crosses treated in a special way, are consistent with the possibility that members of adjacently formed, twin asci are frequently, or even regularly, alike with respect to phenotype distribution class.
A POPULATION STUDY OF CHARA ZEYLANICA IN TEXAS, OKLAHOMA, AND NEW MEXICO
Authors: III Dana G. Griffin , Proctor V. W.
Published: January 2018

Examination of 140 collections of Chara zeylanica from 3 southwestern states shows that a strong dichotomy exists in the collections. Some produce 4‐plated antheridia while others produce 8‐plated antheridia. Absolute separation of the study material is possible on the basis of plate number. In addition, 3 other characters (length/width ratio of oospores; fertility of first branchlet node; and number of distal ecorticate branchlet internodes) show strong correlation with the antheridial type. Preliminary chromosomal work indicates that a segregation at this level may also be possible. In 4‐plated collections examined, n = 28; 8‐plated collections are usually n = 56; however, a few 8‐plated collections are n = 42. No conclusion has been reached regarding the status of the latter collections.