bluuebunny/crossref_metadata_2025 huggingface dataset:
APERTURE EVOLUTION IN THE POLLEN OF PRIMITIVE ANGIOSPERMS
Authors: Walker James W.
Published: January 2018

Diversity of pollen apertures in 35 families of the ranalean complex is compared through a series of representative scanning electronmicrographs, and the evolution of pollen aperture types in primitive angiosperms is outlined. A classification of pollen apertures found in the ranalean complex is presented, and ten basic aperture types are recognized: anasulcate, anatrichotomosulcate, zonasulculate, anaulcerate, catasulcate‐cataulcerate, inaperturate, disulculate‐diulculate, forate, colpate, and porate. Evidence is adduced for the primitive (ancestral) status of anasulcate pollen, and transitional stages in the evolution of other pollen aperture types in the ranalean complex are examined. From an early stock of ranalean angiosperms with anasulcate pollen, there appears to have been development of a number of interesting but evolutionally dead‐end lines, represented among others by zonasulculate, anaulcerate, and catasulcate‐cataulcerate pollen types. The most important evolutionary trend in early angiosperm pollen seems to have been the development of inaperturate pollen grains in many families of primitive angiosperms, from which there was a second major radiation of aperture types, including evolution of disulculate and forate pollen. Comparative study of pollen apertures observed in living primitive angiosperms suggests a de novo origin of the uniquely angiospermous (dicotyledonous) colpate pollen type from such inaperturate pollen.
THE GEOGRAPHICAL DISTRIBUTION OF B‐CHROMOSOMES OF XANTHISMA TEXANUM DC. (ASTERACEAE). I. SURVEY OF THE RANGE
Authors: Semple John C.
Published: January 2018

The distribution of B‐chromosomes throughout the range of Xanthisma texanum has been determined from approximately 750 individuals from 80 wild populations in Texas, Oklahoma, and New Mexico. Counts of meiotic chromosome figures of n = 4II + 1 BI and n = 5II (4II + IBII) are reported for the first time for subsp. texanum var. texanum and for subsp. texanum var. orientalis. The wide occurrence of B‐chromosomes in natural populations of subsp. drummondii is also documented. B‐chromosomes are present in 22 (27.2%) randomly distributed populations whose characteristics are in no way distinct from populations without B‐chromosomes. In populations with B‐chromosomes present, 19.8% of the plants contained one or two B‐chromosomes, but in total only 5.8 % of all plants contained one or two B‐chromosomes. All populations in one isolated population group of subsp. drummondii lack B‐chromosomes.
CAULINE VASCULATURE AND LEAF TRACE PRODUCTION IN MEDULLOSAN PTERIDOSPERMS
Authors: Basinger James F. , Rothwell Gar W. , Stewart Wilson N.
Published: January 2018

Medullosa and Sutcliffia specimens from the Paleozoic of North America and Europe are examined to determine the architecture of the cauline vasculature and mode of leaf trace production. Emphasis is placed on the identification and characterization of protoxylem strands and their relationship to leaf trace production. Organization of the primary xylem varies from a single protostele to a dissected stele composed of two to many more or less independent bundles. In Medullosa the bundles of primary xylem are each surrounded by secondary xylem, forming separate segments of vascular tissue (‘steles’ of previous workers). These vascular segments may divide and fuse at different levels in the stem. A definite number of protoxylem strands occur near the periphery of the primary xylem. The protoxylem strands divide at intervals producing protoxylem to the departing leaf traces. Leaf traces thus formed arise from all the vascular segments in a coordinated and predictable way and pass outward through emission areas in the secondary xylem. This type of cauline vascular architecture is compared to that of other seed plants. The vascular system of Medullosa stems is interpreted as a dissected monostele. Sympodial vascular architecture has apparently evolved from a protostele separately within the medullosan pteridosperms.
A CYTOGEOGRAPHIC STUDY OF ERIOPHYLLUM LANATUM (COMPOSITAE, HELENIEAE)
Authors: Mooring John S.
Published: January 2018

Analysis of 368 plants derived from 239 natural populations showed that this taxonomically perplexing and wide‐ranging species‐complex consists of diploids (n = 8), tetraploids, hexaploids and octoploids. Microsporocytes were the source of most of the chromosome counts. Meiosis was basically regular. Multivalent formation was uncommon, but 11 % of all the plants examined had one or more full‐sized extra chromosomes. The frequency of plants with extra chromosomes varied significantly among the taxa, from 0 (five varieties) to over 20 % (two varieties). Except in one instance, where one population yielded a diploid and a triploid, different ploidy levels were not found in the same population. The frequency of diploid, tetraploid, hexaploid and octoploid populations was, respectively, 71, 22, 4 and 2%. Variety obovatum appears to be exclusively diploid, and var. aphanactis exclusively tetraploid. Diploids and one or more polyploid levels occurred in the other taxa. No correlation was found between polyploidy and geological history, soils, topography or climate, nor were the polyploids more widely distributed than the diploids. Some of the polyploid populations seem to have been derived from inter‐varietal hybridizations, but others do not. The complex has a “pillar” structure in which 10 diploid taxa support a three‐level polyploid superstructure. The available evidence suggests that the major role of polyploidy here has been to stabilize the products of intra‐ and inter‐varietal hybridizations.
A NEMATODE‐DESTROYING HYPHOMYCETE FORMING PARALLEL MULTISEPTATE HYALINE CONIDIA IN CIRCULAR ARRANGEMENT
Authors: Drechsler Charles
Published: January 2018

In several Petri plate cultures that had been inoculated with decaying plant detritus from central Maryland, a fungus developed which attacks nematodes by extending a rather wide infection‐tube either from an adhesive hyphal protuberance, or, more often, from a subglobose adhesive cell produced terminally on its elongate‐ellipsoid pluriseptate hyaline conidia. A number (sometimes three) of these conidia are borne simultaneously in peripheral positions on the broadly rounded tip of the colorless condiophore, and are directed upward, parallel to the conidiophore axis. From the segment immediately below its adhesive cell, each conidium puts forth laterally a flexible unicellular tubular appendage that grows downward approximately to the level of the spore attachment. The fungus is described as Haptocara latirostrum gen. n., sp. n. Although presumably belonging in the Moniliaceae, it shows no close kinship with the numerous interrelated clampless Hyphomycetes that have been made known as subsisting through capture of nematodes.
SIZE‐CLASS STRUCTURE OF THREE STREAMSIDE FORESTS
Authors: Johnson Forrest L. , Bell David T.
Published: January 2018

Analysis of size‐class distribution in three streamside forest stands in central Illinois shows close agreement of observed data with the negative power curve model of tree size‐class distribution. However, examination of the size‐class distribution of selected species reveals a number of deviations from the model. Most of the deviations from the model can be explained in terms of disease and land use.
HISTOLOGY AND INHERITANCE OF THE CLOSED FLOWER IN CARTHAMUS TINCTORIUS (COMPOSITAE)
Authors: Dillé John E. , Knowles P. F.
Published: January 2018

Three different closed flower types were identified in safflower and were classified as arrowhead, bar, and cage. Histological observations revealed that the closed flower condition is caused by a differentiation of epidermal cells into papillae that become interdigited. The primary difference between the three types is the length of the fused edge along the petal lobe. The papillae are pointed and have thickened walls of cutin. Reduced seed set results from changes in the internal environment during microsporogenesis. The expression of each closed flower type is governed by a single gene; the arrowhead, bar, and cage types have, respectively, the genotypes arar, baba, and coca.
INHERITANCE OF SEX IN ACHLYA BISEXUALIS
Authors: Lasure Linda L. , Griffin David H.
Published: January 2018

Parental crosses, backcrosses, repeated backcrosses, and sib matings with several strains of Achlya bisexualis Coker and Couch have been made. Progeny were tested for sexual reaction with the parental strains. The distribution of sex observed could not be explained on the basis of any simple gene or chromosomal mechanism. Two factors were suggested which may affect the distribution of sex. They are selfing in the female and the complexity of the hormonal system which controls the expression of sex. The inheritance of a cycloheximide‐resistant mutant argues against selfing; however, further studies with other genetic markers are needed.
STOMATAL MOVEMENTS ASSOCIATED WITH POTASSIUM FLUXES
Authors: Dayanandan P. , Kaufman Peter B.
Published: January 2018

Association of potassium ions with stomatal movements is reported here for 22 different plants. These include Ophioglossum engelmanni, Ginkgo biloba, and Pinus sylvestris. In all 22 plants potassium migrates into the guard cells when stomata open in response to light. In addition, potassium migration into guard cells also occurs with night opening in Crassula argentea and with rhythmic opening in Mimosa pudica. Potassium inside the guard or subsidiary cells, conventionally detected through light microscopic observations of epidermal peels treated with sodium cobaltinitrite reagent, may also be mapped by x‐ray microanalysis of such histochemically treated peels, as was the case in this study. In addition to the potassium migration, we also show the movement of chloride as an accompanying anion in Ophioglossum engelmanni, Ginkgo biloba, Plantago rugelii, Begonia sp., and Avena sativa. Eight plants are shown to accumulate potassium inside the stomatal initials or cells of immature stomatal apparatuses; ordinary, immature epidermal cells do not show such an accumulation of potassium. A list in the discussion indicates all the plants in which potassium fluxes associated with stomatal movements have so far been established, including the new examples reported in this paper.
COMPARATIVE ELECTROPHORESIS AND ISOZYME ANALYSIS OF SEED PROTEINS FROM CULTIVATED RACES OF SORGHUM
Authors: Shechter Yaakov , de Wet J. M. J.
Published: January 2018

Comparative disc electrophoresis of acidic proteins, basic proteins, and isozymes of esterase, MDH, and peroxidase were performed with aqueous extracts of seeds from seven cultivars belonging to five races of Sorghum bicolor ssp. bicolor: bicolor, caudatum, durra, guinea, and kafir. Two disc electrophoretic systems were employed. Acidic proteins were electrophoresed in an anionic system (tris‐glycine buffer, pH 8.3). Basic proteins were electrophoresed in a cationic system (β‐alanin‐acetate buffer, pH 4.5). Soluble proteins were stained with Coomassie brilliant blue. Isozyme activity was detected by using specific enzyme stains and substrates. Each cultivar yielded reproducible, characteristic patterns of distinct acidic and basic proteins. Cultivars belonging to the same race produced identical protein and isozyme patterns. The degree of electrophoretic similarity among races was estimated by calculating similarity index values for each of the 10 possible pairs of races. Bicolor, caudatum, durra, and guinea produced very similar acidic and basic protein patterns and esterase, MDH, and peroxidase isozyme patterns. Differences, however, were observed among all races. All of kafir patterns were significantly different from the patterns of other races. Comparative electrophoresis may provide a new source of taxonomic characters for investigating phenetic and phylogenetic relationships in Sorghum.
DNA CONTENT AND EVOLUTION IN THE MICROSERIDINAE
Authors: Price H. James , Bachmann Konrad
Published: January 2018

Relative 2C nuclear DNA contents were microphotometrically determined from nuclei isolated from eight species of Microseris, four species of Agoseris, and Phalacroseris Bolanderi. The thirteen species are diploid (2n = 18) western North American members of the subtribe Microseridinae, tribe Cichorieae, of the family Compositae. A 7.7‐fold variation in DNA content was detected. Phalacroseris has the highest DNA content and Agoseris heterophylla has the lowest. Within the genera Microseris and Agoseris, a 2.8‐ and 3.1‐fold range in DNA content was detected. The higher values were from perennial species, and the lower values were from annual inbreeding species. Both evolutionary increases and decreases in nuclear DNA content have apparently occurred during the differentiation of the subtribe.
STUDIES OF PACIFIC ISLAND PLANTS. XXIX. BLEASDALEA AND RELATED GENERA OF PROTEACEAE
Authors: Smith Albert C. , Haas Judith E.
Published: January 2018

The genus Kermadecia (Proteaceae), originally described as endemic to New Caledonia, has been expanded in recent decades to include three species from the New Hebrides and Fiji. Specialists on the Proteaceae have suggested that the three Melanesian species were generically misplaced, and careful reexamination supports this viewpoint. It is now apparent that a distinct group within the subfamily Grevilleoideae is composed of the genera Euplassa (endemic to South America), Sleumerodendron (a monotypic New Caledonian genus), Gevuina (based on a single South American species but recently expanded to include two other species from Queensland and New Guinea), and the three questionable Melanesian species. A review of this cluster of taxa indicates that Gevuina should again be interpreted as restricted to South America and that the generic name Bleasdalea F. v. Muell. ex Domin should be adopted for a group of five species extending from Queensland and New Guinea to the New Hebrides and Fiji. The relationships of the four genera are discussed and within Bleasdalea four new combinations are proposed: B. bleasdalei (F. v. Muell.), B. ferruginea (A. C. Sm.), B. vitiensis (Turrill), and B. lutea (Guillaumin). Kermadecia, very distinct from the four genera under present consideration, is again interpreted as a New Caledonian endemic.
FLORAL ANATOMY IN THE SAXIFRAGACEAE SENSU LATO. I. INTRODUCTION, PARNASSIOIDEAE AND BREXIOIDEAE
Authors: Bensel Carolyn R. , Palser Barbara F.
Published: January 2018

The floral morphology and anatomy of one representative of the Parnassioideae and two of the Brexioideae are described, and some of the recent literature dealing with the Saxifragaceae sensu lato is reviewed. Comparison of the floral structure in Parnassia to that typical of the Saxifragoideae, the subfamily constituting the Saxifragaceae sensu stricto and which, therefore, may be considered to show the basic saxifragaceous characteristics, reveals little similarity. Parnassia differs in pattern of both sepal and androecial vascularization, vascularization and degree of connation of the carpels, height in the gynoecium to which ventral bundles remain compound, possession of nectariferous staminodia, and the absence of epidermal appendages. Brexia and Ixerba (both of the Brexioideae) are strikingly dissimilar in floral structure and probably should be dissociated. While the position of Ixerba is problematical, it shares more floral characters with the Escallonioideae than with either Brexia or the Saxifragoideae and is better associated with that taxon. In both Parnassia and Brexia the vascular pattern suggests derivation of the androecium from a fascicled condition: the vascular supply of each filament consists of a cylinder of closely associated collateral bundles, and each staminodial set receives a single vascular complex which subsequently divides into as many vascular strands as there are staminodia in the set.
CENTRUM DEVELOPMENT IN DIDYMOSPHAERIA SADASIVANII (PLEOSPORALES)
Authors: Luttrell E. S.
Published: January 2018

Development of a typical pseudoparaphysate centrum in Didymosphaeria sadasivanii Ramachandra‐Reddy indicates that this ascomycete is properly placed in the Pleosporaceae despite the fact that forcible discharge of ascospores from bitunicate asci has not been demonstrated. The relatively thin‐walled asci releasing ascospores within the ascocarp in D. sadasivanii, as in Cochliobolus spp., probably were derived by reduction from the bitunicate type. Ascocarps matured on malt agar slants but developed more rapidly and normally on autoclaved alfalfa stems inoculated in medicine bottles and transferred to moist filter paper in large petri dishes when covered by mycelium.
NATURAL HYBRIDIZATION AND EXTINCTION OF A POPULATION OF PHYSALIS VIRGINIANA (SOLANACEAE)
Authors: Hinton W. Frederick
Published: January 2018

A population of Physalis virginiana (Solanaceae) in Durham Co., North Carolina, which comprised about 40 individual plants in 1968, was reduced in size to four depauperate plants which were collected and studied in 1973. Concomitant with this reduction in population size is an increase in the proportion of individuals showing evidence of hybridization with the closely related P. heterophylla, also growing in the vicinity, from no evidence of hybridization in 1968 to 75% hybrid individuals (3 out of 4 surviving plants) in 1973. Two possible reasons are postulated for this hybridization: scarcity of P. virginiana pollen for cross‐fertilization in this self‐incompatible species and superiority of vegetative growth of hybrids in a changing habitat that has become unsuited for the survival of P. virginiana.
EQUISETUM CLARNOI, A NEW SPECIES BASED ON PETRIFACTIONS FROM THE EOCENE OF OREGON
Authors: Brown John Thomas
Published: January 2018

Equisetum clarnoi is described from four silicified stem fragments and numerous small roots from the Eocene Clarno Chert of Jefferson County, Oregon. Stems are up to 8.0 mm in diam and have sunken stomata arranged vertically in a single line flanking each of the external biangulate stem ridges, features that clearly ally this species with the subgenus Hippochaete. External stem ridges are equal in number to the carinal hypodermal bands. The hypodermis is composed of fibers and has prominent carinal bands up to 0.75 mm long and shorter vallecular bands. Cortical parenchyma cells enclose prominent vallecular canals which are lined by specialized thick‐walled parenchyma cells. The double, common endodermis has prominent casparian strips. Vascular bundles are composed of four to seven metaxylem tracheids flanking each side of the phloem and protoxylem tracheids which occur singly on the internal surface of the small carinal canals. Leaf sheaths in cross section have an adaxial fibrous layer and an external or near external fibrous bundle. Roots are up to 2.0 mm in diam and have paired cuboidal epidermal cells from which root hairs arise. The stele of the root is central and shows exarch primary xylem maturation. Equisetum clarnoi most closely resembles the extant Equisetum hyemale var. affine.
DEVELOPMENTAL ANATOMY OF CORALLOID ROOTS IN CYCADS
Authors: Milindasuta Boon‐earn
Published: January 2018

Coralloid roots of cycads were found to originate endogenously from the pericycle of apogeotropic secondary roots or adventitious roots that have become exposed or nearly exposed to the soil surface. All mature coralloid roots are susceptible to infection by algal endophytes, which seem to enter from the soil through a break in the dermal layers.

In the coralloid roots the algae inhabit intercellular spaces in a definite zone that arises from the protoderm, and in which the cells elongate radially following algal infection. The zone is completely surrounded by a persistent rootcap which is interpreted by most authors as a secondary cortex. The secondary cortex was shown to be derived from the rootcap in this investigation.
THE GLYCOCALYX AND INITIATION OF EXINE SPINULES ON MICROSPORES OF CANNA
Authors: Rowley John R. , Skvarla John J.
Published: January 2018

Spinules of Carina generalis pollen are initiated within a tridimensional network during the microspore tetrad period. The network is stained selectively with the hydrazide‐silver proteinate method of Thiéry following periodate oxidation and by phosphotungstic acid at low pH, demonstrating the presence of polyanions. Protein is indicated as a component of the network by positive staining with PTA in acetone. These results suggest the presence of polysaccharides and proteins, possibly as mucopolysaccharides or glycoproteins. The network may be considered as a part of the glycocalyx because of its composition and association with the plasma membrane. Sporopollenin accumulates on the tridimensional network or in meshes of the net. The beaded fine structure of spinules resists the acetolysis mixture of Erdtman. Our results imply that the plasma membrane and its glycocalyx are part of the system which mediates genetic expression of exine form. The implication is compatible with formation of specific exines on all pollen grains of a plant and on aborted microspores, diminutive spores with depauperate chromosome complements, and enucleate bodies of cytoplasm resulting from meiotic abnormalities.
PHOTOSYNTHETIC AND CHLOROPLAST ULTRASTRUCTURAL CONSEQUENCES OF MANGANESE DEFICIENCY IN SOYBEAN
Authors: Weiland R. Timothy , Noble Reginald D. , Crang Richard E.
Published: January 2018

Soybean plants (Glycine max ‘Harasoy’) grown in horticultural perlite with a manganese‐deficient nutrient solution, developed typical deficiency symptoms of interveinal chlorosis and necrosis. A decrease in photosynthetic rate, dry leaf weight, leaf area, chlorophyll content, and chloroplast number was observed in plants displaying the deficiency. Transmission electron microscopy of manganese‐deficient leaf tissue revealed disorganization in the chloroplast lamellar network, nonhomogeneous distribution of the stroma, and a reduction in quantities of starch, which became increasingly more acute from nodes three to five in plants 28 days postgermination. The data suggest that manganese functions both as a requirement in the photosynthetic apparatus and as a structural component in the lamellar membrane.
DNA CONTENT OF SEVEN SPECIES OF ASTEREAE AND ITS SIGNIFICANCE TO THEORIES OF CHROMOSOME EVOLUTION IN THE TRIBE
Authors: Stucky Jon , Jackson R. C.
Published: January 2018

Relative amounts of nuclear DNA were determined in root tip cells of seven species of Astereae: Aster hydrophilus Greene, A. oblongifolius Nutt., A. riparius H.B.K., Machaeranthera boltoniae (Greene) Turner and Home, M. brevilingulata (Sch‐Bip.) Turner and Home, M. parviflora Gray, and M. tenuis (S. Wats.) Turner and Home. The results show that A. hydrophilus and M. brevilingulata, with a chromosome number of n = 9, have less nuclear DNA than other closely related species which are either n = 4 or n = 5. Cytological analyses of meiosis in the intergeneric hybrid M. parviflora X A. hydrophilus showed cells with two or more small chromosomes of the latter species pairing with single large chromosomes of the former. Pachytene cells of the hybrids M. parviflora X A. hydrophilus, M. parviflora X A. riparius, and M. boltoniae X M. tenuis showed some unpaired chromosome segments. The significance of these results to chromosome evolution in the tribe Astereae is discussed.
THE ORIGIN OF AGROPYRON SMITHII
Authors: Dewey Douglas R.
Published: January 2018

The hypothesis that North American octoploid Agropyron smithii Rydb., 2n = 56, originated by hybridization between tetraploid Agropyron and Elymus species, followed by chromosome doubling, was tested by observing chromosome pairing in hybrids of A. smithii with an induced amphiploid, 2n = 56, derived from E. canadensis L., 2n = 28, X E. dasystachys Trin., 2n = 28, F1's. Chromosome pairing in A. smithii averaged 0.52I, 27.70II, 0.01III, and 0.01IV in 184 metaphase‐I cells; and the amphiploid averaged 1.13I and 27.44II in 195 cells. Chromosome pairing in A. smithii X amphiploid hybrids averaged 8.20I, 23.38II, 0.34III, and 0.05IV in 101 metaphase‐I cells. It was concluded that A. smithii was genomically similar to the E. canadensis‐E. dasystachys amphiploid. The basic genome formula of the amphiploid is SSHHJJXX, with the SSHH genomes coming from E. canadensis and the JJXX genomes coming from E. dasystachys. Consideration of the morphological, ecological, and reproductive characteristics of all North American species that contain the basic SSHH and JJXX genomes led to the conclusion that A. dasystachyum (Hook.) Scribn., SSHH, and E. triticoides Buckl., JJXX, are the probable progenitors of A. smithii.
EVOLUTION OF THE LATICIFER IN EUPHORBIA AS INTERPRETED FROM STARCH GRAIN MORPHOLOGY
Authors: Mahlberg Paul G.
Published: January 2018

The morphology of plastid starch grains from several succulent and nonsucculent species of Euphorbia was examined in parenchyma and in non‐articulated laticifiers. Several classes of grains were identified: small oblong‐round, rod, somewhat osteoid, osteoid, lobed osteoid, discoid, and round grains. Parenchyma possessed only small oblong‐round grains, whereas grains of different morphology were present in laticifers. Different species of this genus can be characterized by the morphology of the large, or mature, starch grains present in the laticifer. The rod‐shaped grain, which was somewhat wider at the midregion than at the ends, was present in several nonsucculent forms, E. terracina, E. pulcherrima and E. heterophylla. The somewhat osteoid grain was represented by the succulent species E. viguieri, E. milii, and E. mauritanica, where the mature grains developed somewhat enlarged ends. Grains with much enlarged ends were represented in the succulent species of E. abyssinica, E. pseudocactus, and E. tirucalli. Alteration of the pattern of starch deposition in which several lobes were formed at the ends of the grain has given rise to a lobed osteoid class (E. inconstantia). Lobes also may be formed with greater frequency along the midregion of the grain in this than in other species. Euphorbia lactea had the most complex grain in which lobing was frequent at the ends as well as along the midregion, resulting in a large discoid grain. Subclasses in which grains differed significantly in length between species were evident in all classes containing several species. The average length of grains in any subclass was similar for subclasses between the classes. The study suggests that the elongated grain of the laticifer was derived from the round or oblong grain present in the more primitive parenchymatous cell. Progressive changes in the pattern of starch deposition have given rise to osteoid and discoid grains of increasing morphological complexity which is interpreted to represent trends in laticifer evolution between different species of Euphorbia as reflected by subtle changes for starch deposition within the plastids of this cell.
SEED DISPERSAL IN VIOLA (VIOLACEAE): ADAPTATIONS AND STRATEGIES
Authors: Beattie A. J. , Lyons N.
Published: January 2018

Surveys of Viola dispersal mechanisms result in the distinction of two major adaptive syndromes: one purely myrmecochorous for the exploitation of seed‐transporting ants, the other partially myrmecochorous (= diplochorous) for the explosive ejection of seeds followed by ant exploitation. Diplochory is exhibited by the majority of Viola species, but myrmecochory is exhibited only by eleven species with limited Eurasian distribution. Morphological and experimental evidence suggests the hypothesis that Viola is basically myrmecochorous but that different selective pressures, especially seed predation, have produced a clear divergence in dispersal systems. The majority of species, the diplochores, have evolved a system which combines ballistic and ant seed dispersal with predator avoidance. Diplochory itself may be a response to predation pressure. The minority of species are purely myrmecochorous, possibly highly coevolved with specific ant species, thus limiting the distribution of the Viola species concerned.
PHOTOSYNTHESIS AND RESPIRATION OF ARCEUTHOBIUM TSUGENSE (LORANTHACEAE)
Authors: Miller J. Roger , Tocher R. D.
Published: January 2018

Dark respiration rates of the aerial shoots of Arceuthobium tsugense, obtained by manometric and IRGA techniques, show production of CO2 to range between 155–300 μl CO2 g‐1hr‐1 with evidence of seasonal variation. Experiments with 14CO2 indicate that the aerial shoots are capable of some photosynthetic CO2 fixation, with 10–15 % of the available 14C incorporated by the plant tissue in one hr. Biochemical characterization of the products of photosynthesis reveals that 80–90 % of the incorporated 14C is ethanol soluble. Ten percent of the ethanol soluble fraction is lipoidal in nature, the rest is H2O soluble. IRGA experiments indicate an apparent photosynthetic CO2 fixation capacity of 80–90 μl CO2 g‐1hr‐1, or 25–30% of the amount of CO2 produced by respiration. The significance of these findings is discussed with respect to nutrition of the parasite and effects upon the host.
A TECHNIQUE FOR THE ANALYSIS OF EPISTATIC GENE ACTION II. THE APPLICATION OF THE METHOD
Authors: Clevenger Sarah , Hagen Charles W.
Published: January 2018

With a method based on probability of phenotypic ratios being produced by crosses involving two pairs of interacting genes, data from genetic studies of Impatiens Sultana Hook. f. (Balsaminaceae) were analysed. Nine genes postulated to control floral color are: P, purple; I and W, white; R, red; O, orange; F, fuchsia; D, red; E, red; S, salmon. Epistatic action was evaluated, but progeny counts were too small for linkage to be determined.
KARYOTYPES OF FIVE PLANT SPECIES WITH DISJUNCT DISTRIBUTIONS IN VIRGINIA AND THE CAROLINAS
Authors: Blair Aaron
Published: January 2018

Five species (Actaea pachypoda, Aralia nudicaulis, Cornus alternifolia, Panax quinquefolius, and Symplocarpus foetidus) display a disjunct distribution between the Mountains and Piedmont in North Carolina, South Carolina, and Virginia. The Piedmont populations are small and have apparently been isolated from the Mountain populations for several thousand years. Karyotype differences among populations were found only in A. pachypoda, and even in this species the differences were slight. The absence of population differences in four species, and the moderate differentiation found in A. pachypoda, indicate considerable cytological stability in these species.
ULTRASTRUCTURE OF THE SUBGLANDULAR CELLS FROM THE FOLIAR NECTARIES OF COTTON IN RELATION TO THE DISTRIBUTION OF PLASMODESMATA AND THE SYMPLASTIC TRANSPORT OF NECTAR
Authors: Wergin William P. , Elmore C. Dennis , Hanny Barbara W. , Ingber Bruce F.
Published: January 2018

Foliar nectaries on the midveins of 7‐cm leaves from cotton (Gossypium hirsutum L., cv. Stoneville 213) were examined by light and electron microscopy. The nectaries consist of external multicellular papillae and internal subglandular tissue that extends from the bases of the papillae to the vascular tissue of the midveins. The subglandular tissue is composed of small parenchyma cells; it does not contain sieve elements or xylem vessels. The parenchyma cells are rich in mitochondria, and their walls contain numerous pit fields having a high concentration of plasmodesmata. The absence of vascular tissue and the significance of the pit fields in the subglandular tissue are discussed in relation to symplastic transport of nectar secretions.
A FERTILE AXIS OF TRILOBOXYLON ASHLANDICUM, A PROGYMNOSPERM FROM THE UPPER DEVONIAN OF NEW YORK
Authors: Scheckler Stephen E.
Published: January 2018

A partially petrified impression of Triloboxylon ashlandicum (Aneurophytales) is the first recognized fertile axis of the genus. Identification of the fertile axis rests on the similarity of its anatomy with that of previously described vegetative specimens. Fertile organs replace some vegetative branches along part of the main axis. Fertile organs are twice dichotomized in one plane and bear elongate sporangia arranged pinnately. Vegetative branches differ in that they bear the ultimate appendages of the plant helically. The latter organs dichotomize many times in one plane. Although similar in size and morphology to the ultimate appendages, the fertile organs are homologous by position and vascular supply to the vegetative branches which they replace. Sporangia of T. ashlandicum dehisce longitudinally and terminate in an apiculate tip. Spores are unknown. Fertile organs of T. ashlandicum resemble those of other Aneurophytales and support the earlier placement of Triloboxylon in the order on anatomical grounds. T. ashlandicum differs from other Aneurophytales, however, by bearing vegetative organs at the distal end of its fertile axis.
ROLE OF ALLELOPATHY AS EXPRESSED BY DOMINATING TREES IN A LOWLAND FOREST IN CONTROLLING THE PRODUCTIVITY AND PATTERN OF HERBACEOUS GROWTH
Authors: Lodhi M. A. K.
Published: January 2018

Low productivity rate and relatively bare areas occur under sycamore, hackberry, red oak, and white oak trees, even though several herbaceous species may grow well under elm trees in the same community which cast just as dense shade. No significant differences were found in amounts of most mineral elements and pH sampled under sycamore, hackberry, red oak, and white oak trees as compared with control soils under elm trees in the adjacent plots. Percent soil moisture was consistently higher under all test trees than under elm trees throughout the growing season. Thus the low productivity rate and relatively bare areas under sycamore, hackberry, red oak, and white oak trees were not due primarily to the factors stated above. Decaying leaves, leaf leachate of all four test species, and soil collected from under test trees significantly reduced seed germination, radicle growth, and seedling growth of selected herbaceous species. Several growth inhibitors, chiefly phenolics, were isolated and identified from sycamore, hackberry, red oak, and white oak leaves and the soils under them. Thus it appears that the low productivity rate and destitute growth under test tree species are due to allelopathy. Ecological significance of allelopathy in a community is discussed.
THE DIATOMS OF TIMPANOGOS CAVE NATIONAL MONUMENT, UTAH
Authors: Clair Larry L. St. , Rushforth Samuel R.
Published: January 2018

The diatom flora of the cavern system of Timpanogos Cave National Monument was investigated. Diatoms were found throughout the cave system and were distributed according to moisture and natural openings. Twenty‐six species were identified and described, including eight not previously collected from caves and four new records for the state of Utah.
CELLULAR SLIME MOLDS OF SOUTHEAST ASIA. I. DESCRIPTION OF NEW SPECIES
Authors: Cavender James C.
Published: January 2018

Sixteen species of cellular slime molds were isolated from Southeast Asian forest soils. Ten of these, Dictyostelium mucoroides Brefeld, D. purpureum Olive, D. polycephalum Raper, D. lacteum van Tieghem, D. rhizopodium Raper and Fennell, D. lavandulum Raper and Fennell, D. vinaceo‐fuscum Raper and Fennell, D. coeruleo‐stipes Raper and Fennell, Polysphondylium violaceum Brefeld, and P. pallidum Olive have been previously described and are well‐recognized species occurring in other parts of the world. Two, one in the genus Dictyostelium and one belonging to the family Guttulinaceae, are considered species by the author but have not been formally described. Four are described in this paper as new: Dictyostelium intermedium, D. multi‐stipes, D. bifurcatum, and Acytostelium subglobosum. A new variety papilloideum of D. lacteum is also described. One other discovery of special interest is an isolate of Polysphondylium violaceum which produces abundant macrocysts, now known to be the sexual stage in the life cycle of cellular slime molds.
THE RELATIONSHIPS AMONG UMBELLIFERONE, GROWTH, AND PEROXIDASE LEVELS IN CUCUMBER ROOTS
Authors: Jankay Peter , Muller Walter H.
Published: January 2018

Umbelliferone decreases the elongation rate and initiates a swelling response in cucumber roots. Associated with these growth effects are increases in peroxidase activity in water soluble, salt soluble, and wall bound fractions. The effect on elongation is reversible and is separated in time from the swelling response. Increased peroxidase levels appear after the elongation rate has been reduced but coincident with the swelling response. It is suggested that umbelliferone effects axial elongation and radial expansion through different mechanisms.
THE EARLY ACTION OF THE FLORAL STIMULUS ON MITOTIC ACTIVITY AND DNA SYNTHESIS IN THE APICAL MERISTEM OF XANTHIUM STRUMARIUM
Authors: Jacqmard A. , Raju M. V. S. , Kinet J. M. , Bernier G.
Published: January 2018

Vegetative plants of Xanthium strumarium (a short‐day species) were induced to flower by exposure to a single 16‐hr long night. By cutting off the induced leaf (half‐expanded leaf) at various times, it was established that, by 8 hr after the end of the long night, a sufficient amount of floral stimulus had reached the meristem to induce a flowering response. The following sequence of events occurred in both the peripheral and central zones of the apical meristem of induced plants: 1) a rise in the mitotic index beginning at 28 hr after the end of the long night and culminating at 36 and 56 hr; 2) a stimulation of DNA synthesis starting at 32–36 hr and reaching a maximum at 60 hr; 3) an increase in nucleolus diameter starting at 32 hr. The cell population in the meristems of both vegetative and induced plants displayed a similar distribution, with about 80 % of the nuclei with the 2C amount of DNA. The comparison of the kinetic data concerning the mitotic index and DNA synthesis indicated that one of the early effects of the floral stimulus in the peripheral and central zones was the release in mitosis of cells whose nuclei were in the postsynthetic (G2) phase of the mitotic cycle. In the pith‐rib meristem, the following events were recorded: 1) a stimulation of DNA synthesis starting at 20 hr; 2) a rise of the mitotic index beginning at 28 hr; 3) the vacuolation and elongation of cells starting at 48 hr. All these events occurred well before the initiation of bract and flower primordia, which began at 96 and 136 hr, respectively. Neither stimulation of mitotic activity nor flowering occurred in the meristems of plants subjected to a long night interrupted at its midpoint by a 5‐min light break. The results are discussed in relation to the early events which are known to occur in the meristems of other photoperiodic species in transition to flowering.
ONTOGENETIC REORGANIZATION OF THE ROOT MERISTEM IN THE COMPOSITAE
Authors: Armstrong J. E. , Heimsch C.
Published: January 2018

The organization of the root meristem in selected Compositae was investigated to determine whether changes in the pattern of cell arrangement occurred during root growth in species other than Helianthus annuus. Embryonic, short, and long primary roots of one species of each of twelve genera were prepared for microscopic examination. Additional intermediate growth stages were prepared for Echinacea pallida. The meristem of embryonic roots showed layers of initials typical for dicotyledons. The meristem in many of the short roots of eight species was reorganized by the development of a secondary columella. The long roots showed patterns similar to the embryonic roots. In three species which maintained closed meristems, two layers of cortical initials were common in the embryonic root, and as a general trend, a single layer of cortical initials became more common during root elongation. The cellular changes that resulted in the initiation of a secondary columella are characterized by the conversion of cortical initials to secondary columella initials by a shift in their plane of cell division. It is proposed that the size and shape of the quiescent center changes as the conversion takes place. No intermediate stages were observed which could account for the reduction of two layers of cortical initials to one layer.
OBSERVATIONS ON THE SHAPE AND EXPOSURE OF STYLE BRANCHES IN THE ASTEREAE (COMPOSITAE)
Authors: Jones Almut G.
Published: January 2018

A survey of over 30 species of Aster and 61 species in other genera of Astereae indicates that the somewhat flattened style branches of perfect disk florets characteristically unfold and spread in a pronate, rather than a supinate manner. While not exhibited in all genera (Baccharis and Conyza are among the exceptions), this phenomenon appears to be restricted to and, therefore, diagnostic for the tribe. The slender style branches of pistillate ray florets display the supinate expansion which is regularly observed in other tribes of Compositae.
MORPHOLOGY, EVOLUTION, AND TAXONOMIC SIGNIFICANCE OF THE INFLORESCENCE IN CORDYLANTHUS (SCROPHULARIACEAE)
Authors: Chuang Tsan‐Iang , Heckard Lawrence R.
Published: January 2018

The genus Cordyhmthus has considerable diversity in its inflorescences while the other genera of tribe Rhinantheae (Scrophulariaceae) uniformly have racemes or spikes. Four distinct inflorescence types are recognized and their homologies and evolutionary history are postulated. Thus it is suggested that the basic florescence type, the elongated spike (Type I), has undergone evolutionary reduction to a few‐flowered spike and ultimately to a single‐flowered florescence (Type II). Further evolution involving processes of compaction and clustering of the single‐flowered florescences has resulted in glomerulate clusters (Type III) and spiciform clusters (Type IV). Knowledge of inflorescence homologies and distribution of the four inflorescence types in the genus has been of considerable aid in formulating a new infrageneric classification. Using evidence primarily from inflorescence, floral, and seed morphology, as well as from geographical distribution and ecology, a classification is proposed establishing three subgenera, namely subg. Dicranostegia, subg. Hemistegia, and subg. Cordylanthus, the last with three sections, sect. Cordylanthus, sect. Anisocheila, and sect. Ramosi.
SEED PROTEIN PROFILES IN THE NARROW‐LEAVED SPECIES OF CHENOPODIUM OF THE WESTERN UNITED STATES: TAXONOMIC VALUE AND COMPARISON WITH DISTRIBUTION OF FLAVONOID COMPOUNDS
Authors: Crawford Daniel J. , Julian Edward A.
Published: January 2018

Water soluble seed proteins from 69 populations representing seven species of Chenopodium were separated electrophoretically. Very little or no intraspecific variation was detected. The use of seed proteins as taxonomic characters was evaluated and compared to data from flavonoid chemistry. Seed proteins are of value in distinguishing C. atrovirens and C. leptophyllum, something which could not be done with flavonoids. Proteins and flavonoid data demonstrated that C. hians and C. leptophyllum are distinct. An analysis of storage proteins failed to differentiate C. desiccatum from C. atrovirens and C. pratericola even though the species are distinct in flavonoids and other characters. Chenopodium atrovirens and C. pratericola produce similar or identical seed proteins, just as they are identical in flavonoids. Seed proteins indicated that plants referable to C. incognitum represent two biological entities, one apparently a minor morphological variant of C. atrovirens and the other conspecific with C. hians. The same interpretation had been given on the basis of flavonoid chemistry. The protein data suggest a close relationship between C. subglabrum on the one hand and C. atrovirens and/or C. desiccatum on the other.
SEASONAL CHANGES IN LEAF SURFACE WAXES OF PICEA PUNGENS
Authors: Reicosky David A. , Hanover James W.
Published: January 2018

The morphological and chronological development of epicuticular waxes and their effects on the boundary layer of blue spruce needles were studied with a scanning electron microscope. Structural or crystalline‐like waxes develop first in the epistomatal chambers of needles in an expanding bud. However, as the needles emerge from the bud the structural waxes develop over the entire needle surface on glaucous foliage but are mainly restricted to the stomatal areas on non‐glaucous foliage. The epistomatal chambers are occluded with surface waxes as the needles emerge from the bud and they remained occluded. Structural waxes occlude the epistomatal chambers but as these waxes degrade the occlusion becomes amorphous in appearance. Structural waxes are degraded to an amorphous layer over the entire needle surface by weathering. Calculations reveal that the surface waxes of blue spruce are too small to have a significant effect on the boundary layer of the needle.
EFFECT OF THE CALYPTRA ON INTERCALARY MERISTEMATIC ACTIVITY IN THE SPOROPHYTE OF FUNARIA (MUSCI)
Authors: French J. C. , Paolillo D. J.
Published: January 2018

The removal of the calyptra from the sporophyte of Funaria causes the seta to thicken dramatically. The growth patterns of the seta‐thickened and normal sporophytes are similar in that in either case elongation proceeds from the activity of an intercalary meristem in the subapical region. The absence of the calyptra during elongation does not inhibit growth. The first effect of removing the calyptra is to allow for increased lateral expansion of the cells produced from the meristem. Subsequently, there is an increase in the number of cells seen in transverse sections, compared to what is seen in normal sporophytes.

Improved procedures for surface sterilization and in vitro culture have allowed the growth of young, excised sporophytes to maturity. Using these culture procedures it is shown for the first time that thickened setae are capable of long term (indeterminate) growth if capsules do not form.

The normal seta is shown to be doubly tapered, with the maximum diameter reached after the first ⅓ of the length of the seta is attained. The tapering of the normal seta seems to result from an interaction between the intercalary meristem and the calyptra, which is also tapered.
STUDIES OF SPERMATOGENESIS IN THE HEPATICAE V. BLEPHAROPLAST DEVELOPMENT IN MARCHANTIA POLYMORPHA
Authors: Kreitner Gerald L. , Carothers Zane B.
Published: January 2018

Coaxial centrioles and a microtubule organizing center (MTOC) constitute each centrosome in spermatid mother cells of Marchantia polymorpha. During cell division the centrosome separates at its midregion and the two centrioles undergo a planar rotation that brings them to lie somewhat staggered and nearly parallel with their proximal ends embedded in osmiophilic granular material similar in appearance to that of the MTOC. Microtubules of the multilayered structure (MLS) arise in this material below the posterior centriole and parallel to its long axis. The rotation of centrioles and the initiation of S1 tubules below the posterior centriole determine polarity of the incipient blepharoplast. Lower MLS strata are formed under the anterior centriole by the compaction of granular, osmiophilic matrix. Formation and growth of S2 vertical lamellae occur at the left front edge of the MLS in association with MTOC‐like matrix localized near the cell membrane. The MLS enlarges to about 0.4 μm wide by 0.6 μm long and is ovoid in outline except for a short distal projection underlying the posterior centriole. Subsequently the lamellae are transformed into homogenous, osmiophilic matrix that contributes directly to the expansion of all MLS strata including microtubules. The stratum of lamellae is interpreted as a planar MTOC subject to morphogenetic control. Each of the four strata grows proximally while the tapering distal projection lengthens beneath the posterior basal body. Dense matrix above the MLS, apparently elaborated by the S2 layer, is organized into cartwheel and triplet components of the basal bodies’ proximal extensions. Organization of triplet tubules proceeds from proximal to distal toward preexisting triplets. Osmiophilic matrix contributes to the formation of microtubule keels and osmiophilic crests and may serve as a cementing material that stabilizes the spatial relationships of blepharoplast components. After full expansion of the MLS’ lower strata, the S2 layer is reorganized into lamellae. Flagellar growth in Marchantia is postulated to involve a process whereby subunits or their precursors are elaborated by the MLS, translocated to the distal end of the flagellum and incorporated into the axonemal tubules. When MLS microtubules elongate to form a long, narrow band, the distal half of the S2 layer is again in the osmiophilic matrix state.