bluuebunny/crossref_metadata_2025 huggingface dataset:
AN EXPERIMENTAL APPROACH TO THE SYSTEMATICS OF THE MONOECIOUS‐CONJOINED MEMBERS OF THE GENUS CHARA, SERIES GYMNOBASALIA
Authors: Proctor Vernon W. , Wiman Fred H.
Published: January 2018

Most monoecious‐conjoined members of the seriesGymnobasalia, genusChora, bear either tetrascutate or octoscutate antheridia. A determination of the extent to which various populations of these two morphologically distinct entities are reproductively isolated was the primary objective of the present study. Experimental crosses were attempted between emasculated sprigs and nonemasculated plants serving as sperm sources. All evidence suggests that tetra‐ and octoscutate populations are reproductively isolated throughout their respective ranges even to the extent of producing black oospores. Crosses were also attempted between geographically isolated tetrascutate, and again octoscutate, populations. All were uniformly successful to the extent that black oospores resulted; but when such oospores were germinated many of the resulting progeny were found to be either nonviable or dwarfed, and frequently self‐sterile as well. This was particularly true where parental clones differed with respect to geographical origin, chromosome number, or external morphological features.
SYNTHETIC HYBRIDS OF HORDEUM BOGDANII WITH ELYMUS CANADENSIS AND SITANION HYSTRIX
Authors: Dewey Douglas R.
Published: January 2018

Seven viable hybrid seeds were obtained from 48 hand‐emasculated Elymus canadensis L., 2n = 28, florets pollinated by Hordeum bogdanii Wilensky, 2n = 14. The hybrids were large, vigorous, and completely sterile plants that bore a closer morphological resemblance to E. canadensis than to H. bogdanii. Chromosome associations in the 21‐chromosome hybrids averaged 9.98I, 5.40II, and 0.08III in 264 metaphase‐I cells. Chromosome pairing was attributed to allosyndetic pairing between E. canadensis and H. bogdanii chromosomes. The H. bogdanii genome appears to be partially homologous with one of the two E. canadensis genomes. One Sitanion hystrix (Nutt.) J. G. Smith X H. bogdanii hybrid was obtained from a cross involving 37 emasculated S. hystrix florets. This triploid, 2n = 21, hybrid was morphologically intermediate between the parents and totally sterile. Averages of 9.09I, 5.72II, and 0.16III were observed in 106 cells at metaphase I. A modified form of the H. bogdanii genome appears to occur in S. hystrix as well as in E. canadensis. Many allotetraploid Agropyron, Elymus, and Sitanion species apparently contain a genome derived from Hordeum.
ASSIMILATION OF 14CO2 BY CATKINS OF CARYA ILLINOENSIS AND APPARENT TRANSLOCATION TO THE POLLEN
Authors: Davis Joel T. , Sparks Daerell
Published: January 2018

Carbon‐14 dioxide and autoradiography were employed to determine if the catkins (staminate inflorescence) of Carya illinoensis Koch ‘Stuart’ are a sink for photosynthates produced by the current season's leaves; to observe 14CO2 assimilation by the catkin at different stages of physiological development; and to determine if photosynthates produced by the catkins are utilized in pollen production. For a brief period in their development, the catkins were a sink for photosynthates produced by the leaves of the current season. The catkins assimilated 14CO2 from time of emergence from the bud until senescence, and photosynthates produced by the catkins were incorporated into the pollen.
NUTRITION OF CHYTRIOMYCES AND ITS INFLUENCE ON MORPHOLOGY
Authors: Hasija S. K. , Miller C. E.
Published: January 2018

The nutrition and its influence on some morphological characteristics of one isolate of Chytriomyces aureus Karling and two isolates of C. hyalinus Karling, one with and one without resting bodies, was studied. All three isolates required exogenous thiamine for optimum growth. Glucose, fructose, mannose, maltose, cellobiose, and starch supported good or moderate amounts of growth of all the isolates. Galactose, arabinose, xylose, ribose, sucrose, lactose, and raffinose supported little or only trace amounts of growth of C. hyalinus, with resting bodies, but failed to produce any growth of C. aureus and C. hyalinus, without resting bodies. All isolates utilized ammonium [NH4NO3, (NH4)2SO4, NH4Cl] as nitrogen sources but were unable to utilize nitrate (KNO3) and nitrite (KNO2). All isolates were able to grow at pH ranges of 5–8; the optimum pH range was 6.5. Both isolates of C. hyalinus were able to grow at a temperature of 10–30 C, whereas C. aureus did not grow below 15 C or above 25 C. Sporangial size was influenced by varying temperature levels, pH ranges, vitamins, carbohydrates, and nitrogen sources, while the morphology and sizes of zoospores, lipoid globules, apophyses, and rhizoids were little affected. The similarity of response exhibited by both species of Chytriomyces to various nutrients may suggest that these are closely related taxa.
EFFECT OF PICLORAM ON TRANSPORT IN YOUNG BEAN, MESQUITE, AND HUISACHE PLANTS
Authors: Leonard O. A. , Glenn R. K. , Bayer D. E.
Published: January 2018

The effect of 4‐amino,3,5,6‐trichloropicolinic acid (picloram) on transport from leaves to the roots was studied using young bean (Phaseolus vulgaris L.), mesquite (Prosopis juliflora var. velutina (Woot.) Sarg.), and huisache (Acacia farnesiana (L) Willd.) plants. The only picloram treatments which were effective in enhancing transport of 14C‐assimilate or 14C‐picloram to the roots were those made to the shoots or roots one day or more before application of the label to the shoots. The enhancement of transport was not evident when un‐labeled picloram or 2,4,5‐trichlorophenoxyacetic acid (2,4,5‐T), or both, were applied at the same time as the 14C‐label. Enhancement of transport was to the more mature stem or root tissues. Inorganic nitrogen applied to nitrogen‐deficient bean plants also increased transport of 14C‐assimilate to the roots, especially the rate.
DEVELOPMENTAL GENETICS IN BARLEY: A MUTANT FOR STOMATAL DEVELOPMENT
Authors: Zeiger Eduardo , Stebbins G. Ledyard
Published: January 2018

The barley mutants eceriferum‐g, which have wax deficiencies in several organs, show an abnormal stomatal development as a pleiotropic effect. The main abnormalities are double and triple stomatal complexes. Minor alterations are present as extra cells that alter the normal sequence of the stomatal row and abnormal subsidiary cells that are either larger, smaller, or displaced from their normal position. These characteristics are present in the 12 independently isolated mutants of the g locus, but could not be found in any of the other eceriferum mutants studied. The morphogenetic origin and a developmental sequence for the abnormalities are postulated.
INTERSPECIFIC INCOMPATIBILITY IN GOSSYPIUM. I. STEM HISTOGENESIS OF G. HIRSUTUM X G. GOSSYPIOIDES
Authors: Phillips Lyle L. , Merritt James F.
Published: January 2018

The hybrid of Gossypium hirsutum X G. gossypioides develops normally until 10–12 nodes have been produced at which time neoplasms form in the cortex, phloem, and pith of the lower portion of the shoot axis. Neoplasms are characterized by irregular whorls of unusually large cells the central portions of which contain apparently cytolysed cells and a reddish‐brown substance that probably represents the products of cytolysis. Neoplastic invasion is followed by inactivation of the vascular cambium, disorganization of the phloem and cortex, and tylosing and plugging of many xylem vessels. Subsequent growth of the shoot, which continues at a very slow rate for up to several years, involves the proliferation of parenchymatous tissue which becomes secondarily vascularized.
CHROMOSOME STUDIES IN WESTERN NORTH AMERICAN COMPOSITAE
Authors: Strother John L.
Published: January 2018

Original chromosome observations including number for 68 taxa representing 47 genera are reported. Of these, 12 are first reports for species representing ten genera. In nine species multivalent associations (rings or chains) were noted; these were not always accompanied by low pollen stainability. Accessory chromosomes (centric fragments or univalents) were noted in two species.
GERMINATION AND SEEDLING RESPONSE OF ATLANTIC AND GULF COASTS POPULATIONS OF UNIOLA PANICULATA
Authors: Seneca Ernest D.
Published: January 2018

Germination response following various periods of cold treatment and seedling response to temperature, daylength, and salinity were studied for several Atlantic and Gulf coasts populations of Uniola paniculata L. Results indicated that Atlantic coast Florida populations did not require cold treatment prior to germination at 95–65 F, but that populations from Virginia and North Carolina did. Gulf coast populations exhibited a germination response intermediate between those just mentioned. Seedling studies revealed that alternating diurnal thermoperiods with daytime temperatures of 80 F and above produced good vegetative growth in all populations with little preference for either short‐ or long‐day conditions. Gulf coast populations produced the most biomass under all treatment conditions. Seedlings from a North Carolina and a Florida population indicated no difference in substrate salt tolerance. Salt tolerance was reduced in the higher temperature thermoperiod for both populations. Seedlings from these two populations produced more biomass in a salt spray treatment than in substrate salinity treatments.
THE FINE STRUCTURE OF GENETIC TUMOR CELLS
Authors: Ames Ira H.
Published: January 2018

Tissue from genetic tumors at an early stage of development on young seedlings of Nicotiana suaveolens x N. langsdorffii was examined with the electron microscope. Such tumors, which first appear on the stem immediately below the petioles of the first and second leaves, are composed essentially of three cell types. They are covered by a single layer of epidermal cells of which two specializations, guard cells and trichomes, were observed. The majority of cells in the tumors are large, irregularly shaped, highly vacuolated, parenchymal cells. Meristematic cells, which are found in clusters close to the surface of the tumor, are the third cell type. A membrane‐bound inclusion was observed within the plastids of all of the cell types within the tumor. It consists of granular material which accumulates within an intrathylakoid space. There are no major differences in ultrastructure between parenchymal cells of genetic tumors and their normal counterparts from stems without any signs of tumor formation.
SELECTIVE INHIBITION OF CELL CYCLE STAGES IN THE ALLIUM ROOT MERISTEM BY COLCHICINE AND GROWTH REGULATORS
Authors: Nagl W.
Published: January 2018

The treatment of root tips of Allium carinatum, Allium cepa, and Allium flavum with colchicine, abscisic acid, kinetin, and indole‐3‐acetic acid, applied in appropriate concentrations, combinations, and durations, makes possible the selective blockade of the cell cycle in G1, G2, any mitotic stage, and between karyokinesis and cytokinesis. Moreover, treatment with abscisic acid followed by a recovery period stimulates polyploid nuclei in mature tissues to divide. Colchicine, kinetin, and indole‐3‐acetic acid applied together cause end‐to‐end association of metaphase chromosomes. These results together with earlier findings suggest that any step of the cell cycle is independently controlled both by specific balance of the growth regulators and by specific synthesis of the nucleic acids.
PITYOSTROBUS PALMERI, A NEW SPECIES OF PETRIFIED CONIFER CONES FROM THE LATE CRETACEOUS OF NEW JERSEY
Authors: Miller Charles N.
Published: January 2018

Description of Pityostrobus palmeri is based on a single specimen from an exposure of the Magothy Formation on Raritan Bay east of Cliffwood, New Jersey. The cone is cylindrical, 15.5 cm long, and 4.5 cm in diam. Numerous ovuliferous scales 30–35 mm long are arranged spirally around the central axis. A bract about 4 mm long subtends each scale and is fused to it for about 2 mm. Two winged seeds occur on the adaxial side of each scale. Although the scale apices are inflated as in Pinus, the vascular system resembles that of Cedrus in being weakly developed throughout the cone. The combination of these and other Pinus and Cedrus features in the fossil precludes assignment of the fossil to either of these Recent genera. This is the first report of a Pityostrobus in North America.
CHROMOSOME NUMBERS AND TAXONOMIC NOTES FOR ROCKY MOUNTAIN UMBELLIFERAE
Authors: Crawford Daniel J. , Hartman Ronald L.
Published: January 2018

Chromosome numbers are reported for 111 collections of Umbelliferae, which represent 38 species belonging to 23 genera. Three of these genera, Aletes, Neoparrya, and Musineon, have not been counted previously. In addition, first counts are presented for Angelica grayi, A, roseana, Cymopterus acaulis, C. bulbosus, C. longipes, C. montanus, Lomatium foeniculaceum subsp. macdougalii, L. megarrhizum, L. nuttallii, L. orientate, and L. simplex. Our reports of polyploidy in Ligusticum ported (hexaploid, 2n = ca. 66) and in Pteryxia terebinthina var. calcarea (tetraploid, 2n = 44) are the first for these taxa. The counts of 2n = 22 for Harbouria trachypleura differ from the previous report of 2n = 20.
THE SYSTEMATIC SIGNIFICANCE OF SEED MORPHOLOGY IN THE NEOTROPICAL CAPSULAR‐FRUITED MELASTOMATACEAE
Authors: Whiffin Trevor , Tomb A. Spencer
Published: January 2018

Seed shape has traditionally been used as a tribal character in the capsular‐fruited Melastomataceae. The seed morphology of the five neotropical tribes—Microlicieae, Tibouchineae, Rhexieae, Merianieae, and Bertolonieae—was studied with scanning electron and light microscopes. On the basis of seed morphology, five seed types are recognized: microlicioid, tibouchinoid, rhexioid, merianioid, and bertolonioid. Each of these types is illustrated and discussed, with some observations on the range of variation found. The genera of these five neotropical tribes were surveyed for seed morphology, and the results are presented here, together with a discussion of their systematic significance. On the whole, seed morphology confirms the existence of five tribes among the neotropical capsular‐fruited Melastomataceae and provides interesting evidence for generic relationships; however, it also calls into doubt the taxonomic disposition of certain genera and the delimitation of these five tribes. The seeds of most genera fit into one of these five basic types, but there are some which do not; these exceptions are discussed in terms of their seed morphology and possible relationships.
RHYTHM OF LEAF DEVELOPMENT AND SENSITIVITY TO PHOTOPERIODIC FLORAL INDUCTION
Authors: Jacobs William P.
Published: January 2018

Some plants require only one 24‐hr cycle of the appropriate photoperiod to be induced to flower; others require seven or more. To try to understand the basis for this striking difference, the length of the leaf plastochron was determined for Xanthium and Perilla in the same experiments in which their sensitivity to various numbers of photoperiodic cycles was measured. The general finding was that for full floral induction there had to be as many 24‐hr inductive cycles as there were days in the plastochron. When the total days in the plastochron were altered by environmental manipulation, the cycles required for floral induction altered in parallel.
A CYTOPHOTOMETRIC STUDY OF NUCLEIC ACIDS AND PROTEINS IN THE SHOOT APEX OF WHITE SPRUCE
Authors: Cecich Robert A. , Lersten Nels R. , Miksche Jerome P.
Published: January 2018

During the annual three‐phase growth cycle of white spruce [Picea glauca (Moench) Voss] the vegetative shoot apex changed in anatomical configuration. Relative amounts of DNA, histones, RNA, and proteins were measured in three cytohistological zones and were related to the anatomical changes during ontogeny. An extended period of DNA synthesis (S) and G2 preceded an increase in the number of apical initial cells which were part of the mammillary apex. While DNA and histones were generally synchronous during ontogeny, the ratio of DNA to histone increased on June 20. This loss of histone and subsequent increases in RNA and cytoplasmic proteins preceded the appearance of needle primordia on next year's apex. We propose that induction of the apex to reorganize and form needle primordia occurred when the DNA was in a 2C condition, following the loss of histone on June 20.
GROWTH REGULATION BY ETHYLENE IN FERN GAMETOPHYTES. II. INHIBITION OF CELL DIVISION
Authors: Edwards Maurice E. , Miller John H.
Published: January 2018

Ethylene, a natural product of sensitive fern (Onoclea sensibilis L.) gametophytes, has been demonstrated to inhibit cell division in light‐grown prothallia. When plants were grown on Knop's solution plus 1 % sucrose under 300 ft‐c or more of white light, all ethylene concentrations from 1–1000 μl/liter reduced the rate of increase of cell number by about one‐half. The over‐all rate of increase of cell number was regulated by various environmental and chemical factors, but regardless of the rate established in control cultures, ethylene treatment of 1–1000 μl/liter produced a relative 50 % depression of cell number. Ethylene was specific for inhibition of cell division and was not a general inhibitor of growth. The ethylene inhibition did not result from a reduction of photosynthesis or energy supply. Further demonstration of ethylene as the active gaseous component resulted when cultures were grown in small enclosed containers with an ethylene absorbent, mercuric perchlorate, and consequently the cell number of gametophytes was restored to the level of unenclosed controls.
THE ABPHYL SYNDROME IN ZEA MAYS. I. ARRANGEMENT. NUMBER AND SIZE OF LEAVES
Authors: Greyson Richard I. , Walden David B.
Published: January 2018

A range of phyllotactic variation in Zea mays has been obtained from progeny derived from a single ‘opposite‐leaved’ plant. Some segregants exhibit a form of alternate phyllotaxy with poor separation between nodes, while others duplicate the original decussate condition. Numerous intermediate examples have also been observed. Some have both spiral and opposite arrangements on the same plant; others, which begin their ontogeny with the normal distichous arrangement, switch at different stages of maturity to spiral or decussate arrangement. Leaves from ABPHYL plants are up to one‐half the width of comparable normal leaves although their length is similar. Since ABPHYL plants may have twice as many leaves as do normal siblings, total area and dry weight of leaf blades per ABPHYL plant are greater than in normal siblings. Leaf width of both ABPHYL and normal plants correlates well with the number rather than the width of epidermal cells.
UNUSUAL CYTOLOGICAL PATTERNS IN MICROSPOROGENESIS AND POLLEN DEVELOPMENT OF EVOLUTIONARY SIGNIFICANCE IN THE MIMULUS GLABRATUS COMPLEX (SCROPHULARIACEAE)
Authors: Tai William , Vickery Robert K.
Published: January 2018

Four populations of Mimulus glabratus var. utahensis Pennell from the Great Basin and seven of M. glabratus var. fremontii (Bentham) Grant from the New Mexico–Texas–northeastern Mexico area were intercrossed and their F1 hybrids grown. Cytology and fertility of both the parental populations and the F1 hybrids were studied. The following cytological abnormalities were observed in microsporogenesis: cytomixis, the stretching of one or more chromosomes from cell to cell; multipolar divisions, separation of the chromosome complement into two or more parts; unequal disjunction; spontaneous polyploidization; and the production of encapsulated pollen tetrads. Typically, these abnormalities were rare or not observed in the parents, were rare in the intravarietal hybrids, but were more common in the intervarietal hybrids. They were closely associated with, in fact were the probably causes of, barriers to gene exchange between these two diploid (n = 15) varieties. Thus, the apparent causes of barriers to gene exchange in intervarietal hybrids are the likely mechanisms for the evolution of aneuploidy and polyploidy so characteristic of the rest of the Mimulus glabratus complex.
EFFECTS OF S‐TRIAZINES ON PROTEIN AND FINE STRUCTURE OF COTYLEDONS OF BUSH BEANS
Authors: Singh B. , Campbell W. F. , Salunkhe D. K.
Published: January 2018

A significant increase in protein content of bean cotyledons resulted by applications of 0.5 ppm of atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine), simazine [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine], terbutryn (2‐methylmercapto‐4‐ethylamino‐6‐isobutylamino‐.s‐triazine), or GS‐14254 (2‐methoxy‐4‐isopropylamino‐6‐butylamino‐s‐triazine) to the foliage of 5‐6 week old bean plants grown in a controlled environment or field conditions. Aen electron microscopic study indicated that in the cotyledonary cells s‐triazines inducd a 2‐fold increase in the number of cisternae of rough endoplasmic reticulum. These treatments also increased the number of vesicles, which apparently contain protein, and the amount of cytoplasmic ribosomes.
THE MORPHOLOGY AND RELATIONSHIPS OF DALECHAMPIA SCANDENS (EUPHORBIACEAE)
Authors: Webster Grady L. , Webster Barbara D.
Published: January 2018

The circumtropical but preponderantly American genus Dalechampia, comprising nearly 100 species of twining vines (or rarely subshrubs), is strikingly isolated within the Euphorbiaceae because of its distinctive bibracteate inflorescences. There has been considerable taxonomic controversy with regard to the relationships of the genus, and it has been suggested that Dalechampia is allied to the tribe Euphorbieae because of a supposed analogy between its inflorescence and the cyathium in the Euphorbieae. Field and laboratory investigations of the common American species D. scandens, together with a comparative survey of related species, have thrown some light on these problems. The Dalechampia inflorescence seems best interpreted as consisting of a terminal staminate pleiochasium (with part of the lateral branches transformed for nectar production), juxtaposed to a 3‐flowered pistillate cyme. The lips of the conspicuous bilabiate involucre are formed by the hypertrophied bracts which subtend the staminate and pistillate cymes. The bisexual inflorescences appear to be distinctly proterogynous, rather than proterandrous, as has been previously suggested. The configuration of the inflorescence—a bilaterally symmetrical pseudanthium—suggests adaptation for crosspollination, but the closing movement of the bracts makes self‐pollination probable in the absence of visits by pollinators. The similarity of the Dalechampia inflorescence to the cyathium of the Euphorbieae appears to be entirely superficial, and both reproductive and vegetative data suggest that Dalechampia is related to taxa of tribe Plukenetieae.
THE SHOOT APICAL ONTOGENY OF THE PICEA ABIES SEEDLING. I. ANATOMY, APICAL DOME DIAMETER, AND PLASTOCHRON DURATION
Authors: Gregory Robert A. , Romberger J. A.
Published: January 2018

Developing embryos in immature Picea abies seeds already have well‐delineated shoot apical meristems with clearly evident cytohistological zonation. During early seedling development the zonation characteristic of gymnospermous apical meristems is attained. Seedling development is also accompanied by an approximately threefold increase in apical dome diameter. The latter approaches a steady state about 140 days after germination. Seedlings display a spiral phyllotaxis consisting of a contact parastichy system, usually of the primary Fibonacci series. As the seedlings age and apical domes enlarge, higher Fibonacci number‐pairs characterize their phyllotaxis. Mathematical analysis of the relation between cumulative leaf number and age revealed that the length of the plastochronic time interval declines from about 18.5 hr to 5.7 hr as seedling age increases from 20 to 140 days.
THE ULTRASTRUCTURE AND PHYSIOLOGY OF PROTEIN BODIES AND LIPIDS FROM HYDRATED DORMANT AND NONDORMANT EMBRYOS OF SETARIA LUTESCENS (GRAMINEAE)
Authors: Rost Thomas L.
Published: January 2018

Embryo protein bodies in S. lutescens have a uniform matrix and contain no globoid or crystalloid inclusions. Their digestion pattern consists of peripheral pitting, and the occurrence of vesicles along the margin of the formed invaginations suggests a controlled release mechanism. Protein bodies from both dormant and nondormant embryos were observed to be in all stages of digestion. Total protein decreases in both during the first 6 hr of hydration. Lipids do not decrease in hydrated dormant florets although a significant reduction does occur in germinating nondormant florets. Dormancy, therefore, may involve a mechanism that does not control processes already derived (protein body digestion) but does inhibit processes first begun by germination.
THE ONTOGENY OF CARBONIFEROUS ARTICULATES: THE APEX OF SPHENOPHYLLUM
Authors: Good Charles W. , Taylor Thomas N.
Published: January 2018

Twig apices of Sphenophyllum lescurianum, S. constrictum, and two new Sphenophyllum taxa are described in transverse and longitudinal section from middle and upper Pennsylvanian age specimens. In all of the species the single apical cell has the shape of a tetrahedron, with a triangular upper surface and three internal cutting faces. Segment cells are produced from each of the cutting surfaces in a dextrorse or sinistrorse direction, depending upon the species. The central portion of each segment cell contributes to the initiation of the procambium, while the remaining outer portion undergoes a vertical and subsequent horizontal division to form segment cells. Segment cells are aligned in vertical tiers beneath the respective apical cell cutting faces, with the individual leaves positioned directly beneath a tier of segment cells. Leaf primordia are first observed as a series of surface undulations below the apex, with an intercalary meristem located directly beneath each primordium. The vegetative apical organization of Sphenophyllum is demonstrated to be very similar to the type of organization found at the stem tips of Catamites and Equisetum.
INFLORESCENCE CHARACTERS AND REPRODUCTIVE PROFICIENCY IN DANTHONIA SERICEA POPULATIONS
Authors: Quinn James A. , Rotsettis James , Fairbrothers David E.
Published: January 2018

The purpose of this research was the comparison of inflorescence and fruiting characters of populations of Danthonia sericea in relation to both latitude and habitat. Mature panicles were collected in 1969 and 1970 from six New Jersey (three well drained and three bog) and four Georgia (two in well‐drained sites and two in seepage areas adjacent to granite outcrops) populations. Data analyses showed significant differences between population groupings based on latitude (New Jersey vs. Georgia) and habitat (well drained vs. wet). Populations from the wetter sites had significantly longer lemmas; populations from the well‐drained sites had a significantly greater number of spikelets per panicle. Number of spikelets per panicle in Georgia populations significantly exceeded that of New Jersey populations, while caryopses in the New Jersey populations were significantly heavier. In both New Jersey and Georgia, populations from the relatively drier sites had significantly heavier caryopses and a greater percentage of florets with caryopses. Since the well‐drained group and the Georgia group both had a greater number of florets and a greater percentage of florets with caryopses, these two groups were shown to have the greatest reproductive proficiency. Possible adaptive significance of differences in number of seed produced and in seed weight is discussed.
INFLUENCE OF PHLOEM BLOCKAGE ON CAMBIAL GROWTH OF SUGAR MAPLE
Authors: Evert R. F. , Kozlowski T. T. , Davis J. D.
Published: January 2018

Circular patches of bark were surgically isolated on the sides of sugar maple (Acer saccharum Marsh.) trees at breast height at various times during the dormant and growing seasons. Subsequently, samples of wood and attached bark were taken from isolated and control sites to determine the effects of isolation of the bark on cambial activity and xylem and phloem development. In control sites cambial activity and xylem and phloem development occurred normally. Isolation of bark during the dormant season (in November, February, or March) prevented initiation of cambial activity and xylem and phloem development in isolated areas of half of the trees. Varying degrees of cambial activity (periclinal divisions) occurred in the remaining isolated areas, but normal cambial activity and xylem and phloem development were prevented. Isolation of bark after initiation of cambial activity and phloem differentiation, but prior to initiation of xylem differentiation, resulted in the formation of very narrow xylem and phloem increments with atypically short vessel members and sieve‐tube members, respectively. The xylem increments consisted primarily of parenchyma cells. Isolation of bark after initiation of xylem differentiation resulted in curtailment of secondary wall formation in the last‐formed part of many increments. The last‐formed vessel members of all these xylem increments were atypically short. Similarly, the last formed sieve‐tube members of corresponding phloem increments were atypically short. The atypically short cells in the xylem and phloem of isolated areas reflected the effect of isolation on the cambial region, viz., the subdivision of all fusiform cells into strands of cells. Ultimately, the strands of short fusiform cells lapsed into maturity, leaving only strands of parenchymatous elements between xylem and phloem.
THE SHELL ZONE: ITS DIFFERENTIATION AND PROBABLE FUNCTION IN SOME DICOTYLEDONS
Authors: Shah J. J. , Patel J. D.
Published: January 2018

Thirty‐five species belonging to various dicotyledonous families were investigated to study the origin, development, and probable function of the shell zone, which is defined as an arcuate zone of cambiform cells delimiting the early axillary bud meristem. It is present in the majority of the investigated plants and five intergrading patterns of origin are described: (i) from the parenchymatized derivatives of the cells of the peripheral meristem of the shoot apex, adaxial to the bud meristem, (ii) from the peripheral meristem of the shoot apex along with the initiation of the early bud meristem, (iii) from the adaxial cells of the bud meristem, (iv) from the derivatives of the cells of the bud meristem at its base, and (v) partly from the parenchymatized cells of the peripheral meristem adaxial to the bud and partly from the adaxial derivatives of the bud meristem. The shell zone loses its identity at different stages of bud development in various species. Its cells ultimately contribute to the ground meristem, procambium, and pith cells of the axis. In Cuminum cyminum and lpomoea cairica the shell zone contributes in bringing about the axillary position of the bud from its early lateral position. In Solarium melongena, derivatives of the shell zone initiate the internodal elongation between the flower or inflorescence and the shoot apex, ultimately shifting the bud to an extra‐axillary position on the internode.
APICAL DOMINANCE, POLARITY, AND ADVENTITIOUS GROWTH IN MARCHANTIA POLYMORPHA
Authors: Binns A. N. , Maravolo N. C.
Published: January 2018

Benzylaminopurine, indoleacetic acid, and the auxin inhibitors transcinnamic acid, triiodobenzoic acid, and dinitrophenol were employed to elucidate the role of apical dominance and hormones during regeneration of thalli and gemmae of Marchantia polymorpha L. The cytokinin suppressed normal gemma germination and led to the development of nodular, callus‐like growths. When removed from the influence of benzylaminopurine, the site and magnitude of normal thallus outgrowths varied with the length of time that the tissue had remained on the cytokinin‐containing medium. This aberrant germination was not influenced by the incorporation of indoleacetic acid into the medium. Exogenous auxin neither accelerated nor inhibited the regeneration of normal thallus growth on excised vegetative discs. Transcinnamic acid and dinitrophenol inhibited regeneration. Auxin reversed this suppression. Triiodobenzoic acid did not significantly affect regeneration. Autoradiographs demonstrated a pronounced accumulation of labelled auxin in the midribs and the acropetal regions of excised thallus discs. This evidence suggests that there is an endogenous, basipetal auxin gradient in Marchantia; that the maintenance of this gradient is vital to normal growth and regeneration of the thallus; and that high endogenous concentrations of cytokinin destroy this polarity by increasing the auxin‐synthesizing capacity of the tissue.
THE LIGHT FACTOR IN THE GERMINATION ECOLOGY OF DRABA VERNA
Authors: Baskin Jerry M. , Baskin Carol C.
Published: January 2018

The majority of the seeds of the winter annual Draba verna L. require light for germination, but light can be given before they are fully after‐ripened and as long as 4 months before temperature and moisture conditions are favorable for germination. Seeds that are exposed to light in late spring, or in late spring and early summer, and then removed to darkness can germinate under favorable temperature and moisture conditions in autumn, even after passing through a long unfavorable (for germination) wetting and drying period at high summer temperatures in darkness. The light requirement for germination probably is not an important factor restricting D. verna to open, well‐lighted habitats.
THE ROLE OF A CYTOPLASMIC GLUCAN DURING MORPHOGENESIS OF SEX ORGANS IN ACHLYA
Authors: Faro Sebastian
Published: January 2018

A water‐soluble polysaccharide extracted from the cytoplasms of Achlya ambisexualis and A. heterosexualis appeared to be a beta‐1,3‐glucan. This conclusion was based on data obtained by subjecting the glucan to infrared spectrophotometry, using Laminarin as a reference standard, and to enzymatic and acid hydrolysis followed by chromatographic examination. During the vegetative phase of the life cycle the glucan accumulates in the cytoplasm. That it could serve as a stored source of energy was indicated by its disappearance (1) from Achlya transferred from a glucose‐containing to a glucose‐free medium and (2) during the initiation, development, and maturation of sex organs. When development of sex organs was blocked by the addition of dimethylsulfoxide (0.1 % v/v) the consumption of stored glucan ceased, but vegetative growth and glucan accumulation continued. These effects of dimethylsulfoxide could be reversed by the addition of an excess of calcium ions.
GERMINATION ECOLOGY OF DANTHONIA SERICEA POPULATIONS
Authors: Lindauer Lawrence L. , Quinn James A.
Published: January 2018

Seed were collected from nine populations of Danthonia sericea on either wet or well‐drained, sandy sites ranging from Georgia to New Jersey. Germination tests were conducted in the laboratory and in field plots established on contrasting habitat types. Factors considered were temperature, light, prechilling, scarification, and after‐ripening. The majority of freshly harvested seed from all nine populations exhibited innate dormancy the intensity of which decreased with age. Dormancy was removed by scarification and prechilling treatments of 60 days. Seed from wet habitats showed significantly greater germination in light (alternating night‐day) than in dark, while seed from well‐drained habitats had a higher germination percentage in dark than in light. Both responses are considered to be physiological adaptations of the populations to their respective habitats. Alternating night‐day temperatures of 15–25 C produced the greatest overall germination for the nine populations; 15–20 and 10–25 C produced the next highest responses. Field observations confirmed that peak germination occurred in the spring, at the time soil temperatures were in the same range found to be optimum in the laboratory. A comparison of the germination responses obtained from six New Jersey populations in field plots on contrasting habitat types further revealed distinctive physiological adaptations for populations from differing habitats.
SCANNING ELECTRON MICROSCOPY AND ELECTRON MICROPROBE ANALYSIS OF SILICIFICATION PATTERNS IN INFLORESCENCE BRACTS OF AVENA SATIVA
Authors: Kaufman Peter B. , LaCroix J. Donald , Rosen Jonathan J. , Allard Lawrence F. , Bigelow Wilbur C.
Published: January 2018

Using scanning electron microscopy, we determined the kinds and distribution of epidermal cell types in Avena inflorescence bracts (glume, lemma, and palea). Electron microprobe analysis of silica deposition in these epidermal cells showed that silica cells constitute one of the important deposition sites. Probe ratio data indicate that the silica deposited is 74 % pure. Significant amounts of silica also become deposited in the trichomes and lesser amounts in the walls of long epidermal cells. None could be detected in the stomata. The possible functional significance of silica deposition in epidermal cells of these bracts is discussed.
INHIBITION OF NITRIFICATION BY CLIMAX ECOSYSTEMS
Authors: Rice Elroy L. , Pancholy Sunil K.
Published: January 2018

Three plots representing two stages of old‐field succession and the climax were selected in each of three vegetation types in Oklahoma: oak‐pine forest, post oak‐blackjack oak forest, and tall grass prairie. Soil samples from the 0–15 and 45–60 cm levels were analyzed every other month for 1 yr for exchangeable ammonium nitrogen and for nitrate. On alternate months numbers of Nitrosomonas and Nitrobacter were determined in the 0–15 cm level. The amount of ammonium nitrogen was lowest in the first successional stage, intermediate in the second successional stage, and highest in the climax stand. This trend was remarkably consistent throughout all sampling periods, all vegetation types, and both sampling levels in the soil. The amount of nitrate was highest in the first successional stage, intermediate in the second successional stage, and lowest in the climax stand in both sampling levels, all vegetation types, and virtually all sampling periods. The numbers of nitrifiers were high in the first successional stage, generally, and decreased to a very low level in the climax. In fact, there was often no Nitrobacter in the climax stands. These results indicate that the nitrifiers are inhibited in the climax so that ammonium nitrogen is not oxidized to nitrate as readily in the climax as in the successional stages. Evidence from other geographic areas and vegetation types strongly supports this conclusion. This would certainly appear to be a logical trend in the evolution of ecosystems because of the increased conservation of nitrogen and energy. The ammonium ion is positively charged and is adsorbed on the negatively charged colloidal micelles, thus preventing leaching below the depth of rooting. On the other hand, nitrate ions are negatively charged, are repelled by the colloidal micelles in the soil, and thus readily leach below the depth of rooting or are washed away in surface drainage. There is growing evidence also that many plant species can use ammonium nitrogen as effectively or more so than nitrate nitrogen. If ammonium nitrogen is used directly, this eliminates four chemical steps because nitrogen which is oxidized to nitrite and then to nitrate must be reduced back to nitrite and then to ammonium nitrogen before it can react with keto‐acids in the formation of amino acids. The two reduction reactions require considerable expenditure of energy.
HORMONE‐INDUCED ENDOREDUPLICATION PRIOR TO MITOSIS IN CULTURED PEA ROOT CORTEX CELLS
Authors: Libbenga Kornelis R. , Torrey John G.
Published: January 2018

One‐mm‐thick cortical explants excised aseptically from 10‐11 mm behind the tip of 3‐day‐old roots of the garden pea, Pisum sativum, cv. ‘Little Marvel’ were cultured on a synthetic nutrient medium supplemented with auxin or auxin and cytokinin. Nuclear DNA contents were measured in cells of the explants at the outset and at specified times during culture up to seven days. Fixed and sectioned preparations were stained with the Feulgen method using the DNA‐specific dye auramin‐O. Fluorescent microspectro‐photometric measurements of individual nuclei were made from each cortical population. At day zero all cortical nuclei measured were either 2c or 4c with respect to their DNA content. In the presence of the auxins, indoleacetic acid and 2,4‐dichlorophenoxyacetic acid, and the cytokinin, kinetin, DNA values increased to multiples of the 2c level with populations at the 8c and 16c level predominating after three days of culture as well as at seven days. In the presence of auxins alone no change in DNA values was observed during three days. Kinetin concentrations as low as 0.01 ppm were already effective. The data are interpreted to show that cytokinin, in the presence of auxin, induces two rounds of DNA synthesis prior to the first mitoses, the first round being connected with chromosome doubling by endoreduplication and the second one with normal mitosis. From this we inferred that tetraploid cells in leguminous root nodules might have arisen in the same way, i.e., by endoreduplication prior to the first mitoses induced by the rhizobial division stimulus, unless the chromosome number of root cortical cells had already been doubled by endoreduplication in the normally differentiating root systems.
THE PSILOPEZIOID FUNGI. III. THE GENUS PSILOPEZIA (PEZIZALES)
Authors: Pfister Donald H.
Published: January 2018

The genus Psilopezia is treated in a restricted sense, limited to three species. Psilopezia is characterized by its flat, appressed apothecia, large ascospores, non‐amyloid asci, and bent or deformed paraphyses. The relationship between Psilopezia and Pachyella is discussed. Species are distinguished by the presence or absence of gel in the apothecium, anatomy of the apothecium, size of the apothecium, and by ascospore size. Descriptions, illustrations, and a key are provided for the included species.
IBYKA AMPHIKOMA, GEN. ET SP. N., A NEW PROTOARTICULATE PRECURSOR FROM THE LATE MIDDLE DEVONIAN OF NEW YORK STATE
Authors: Skog J. E. , Banks H. P.
Published: January 2018

Ibyka gen. n. is described from late Middle Devonian compressions and petrifactions collected in eastern New York State. It is a robust plant of which three orders of branching and ultimate appendages (leaves) are known. The latter dichotomize up to five times, are arranged spirally on all orders of branching, are three‐dimensional, and all orders are terete in cross section. Fertile appendages, homologous with the sterile, are terminated by sporangia. The protostele has five or six arms, the maturation is mesarch, and the protoxylem disintegrates leaving lacunae at the tips of the arms. Traces to appendages are terete and arise spirally from the tips of the arms. The primary xylem consists of tracheids only, the phloem of thin‐walled cells and probable tanniniferous cells. The cortex consists of parenchyma and groups of sclereids. Secondary xylem is lacking. Ibyka is placed in a new order, Ibykales, close to the Hyeniales (protoarticulates) and to the Pseudosporochnales all three of which probably evolved from Trimerophytina.
PHENOLIC COMPOUNDS ASSOCIATED WITH DEVELOPMENT IN THE LIVERWORT MARCHANTIA POLYMORPHA
Authors: Reynolds A. C. , Maravolo N. C.
Published: January 2018

Extracts of Marchantia polymorpha contain substances which, in vitro, strongly inhibit or enhance indoleacetic acid oxidation by both horseradish peroxidase and an IAA oxidase enzyme from M. polymorpha. The extracts can be partially freed of such activity by dialysis, passage through a column of polyvinylpyrrolidone powder, or extraction with an anion exchange resin. Chromatographic separation of the extract revealed the presence of four as yet unidentified phenolic compounds. Two inhibited and two enhanced IAA oxidase activity. Inhibitory activity was not destroyed by horseradish peroxidase in the absence of IAA. The level of these compounds in various regions of thallus was measured. Inhibitors were present throughout the tissue, with some localization in the basal and apical areas; there was an acropetal gradient of increasing cofactor concentration.
SEED DEVELOPMENT IN CITRUS WITH SPECIAL REFERENCE TO 2X X 4X CROSSES
Authors: Esen Asim , Soost Robert K.
Published: January 2018

Comparative cytological and histological studies during embryogenesis of seeds from 2x X 2x and 2x x 4x crosses indicate that the ratio of ploidy level between embryo and endosperm is the most important factor affecting the course of seed development. The crosses produced seeds with the expected ploidy relationships between embryo, endosperm, and maternal tissue of 2:3:2 and 3:4:2 as well as the anomalous relationships 3:5:2, 4:6:2, and 6:10:2. All but 3:4:2 resulted in normal, germinable seeds. The ploidy level of the maternal tissue in relation to that of the embryo or endosperm did not appear to have any effect on seed development. About 92–99 % of seeds from 2x x 4x crosses containing triploid embryos with tetraploid endosperm aborted at different stages of embryogenesis. The abortion in all cases was preceded by abnormalities in the tetraploid endosperm. It is postulated that the unbalance of chromosome number between embryo and endosperm disturbs physiological relationships between these two tissues, leading first to the abortion of the endosperm and then of the embryo.
A NEW VOLTZIALEAN CONE BEARING SEEDS WITH EMBRYOS FROM THE PERMIAN OF TEXAS
Authors: Miller Charles N. , Brown John Thomas
Published: January 2018

Description of the new cone is based on a single specimen from the Lower Permian Leonard Series of west Texas. The cone is 2.0 cm in diam. It has numerous fertile dwarf shoots subtended by ovate nonbifurcate bracts arranged in a compact spiral around the axis. The dwarf shoots are free from their subtending bracts and equal them in length. Each dwarf shoot is dorsiventrally flattened and bears about 30 sterile scales each of which is ovate and has a single vascular strand. These sterile scales are in spiral sequence but are lacking on the medial adaxial side of the dwarf shoot. A single flattened erect ovule is attached at the base on the adaxial side of the dwarf shoot and equals it in length. Tracheids and elongate parenchyma cells enclosed by the megaspore wall of one seed give evidence of the oldest embryos on record. Their occurrence in seeds that remain in the cone indicates that the kind of development in most modern plants, in which embryo growth precedes seed dispersal, had evolved by Lower Permian time. Moyliostrobus texanum gen. et sp. n. combines features typical of the Lebachia and Ernestiodendron types of cones.
POLLEN STUDIES IN THE GENUS CORDIA (BORAGINACEAE)
Authors: Nowicke Joan W. , Ridgway John E.
Published: January 2018

The pollen of 40 species of Cordia L. was studied by light microscopy and scanning and transmission electron microscopy. Three major types were found, 3‐porate with a reticulate sexine, 3‐colpate to 3‐colporoidate with a striatoreticulate sexine, and 3‐colpate to 3‐colporate with a spinulose sexine. These pollen types are correlated with significant differences in the inflorescence, flower, and fruit structures found in the sporophyte. The following revisions are suggested and discussed: that Cordia sect. Varronia P. Br. be elevated to generic status; that Cordia sebestena L. and a few close allies be treated as generically distinct; and that Cordia myxa L. be conserved as the lectotype for the genus, thus continuing a wide application of the epithet Cordia.
CHROMOSOME NUMBERS IN MEXICAN ASTERACEAE
Authors: Turner B. L. , Powell A. M. , Watson T. J.
Published: January 2018

Chromosome numbers are reported for 100 collections distributed among 68 species and 46 genera of Mexican Asteraceae. Included are systematic discussions regarding chromosome numbers of the following taxa: Haplopappus spinulosus var. scabrellus (n = 4, 8); Hofmeisteria fasciculata (n = 19), Malperia tenuis (n = 10), and Pleurocoronis laphamioides (n = 9); Cymophora pringlei (2n = 16); Plummera (n = 15); and Porophyllum tridentatum var. crassifolium (n = 15) as related to Chrysactinia and Nicolletia.