bluuebunny/crossref_metadata_2025 huggingface dataset:
THE CYTOLOGY OF POLLEN ABORTION IN C‐CYTOPLASMIC MALE‐STERILE CORN ANTHERS
Authors: Lee Sheu‐Ling Janet , Gracen V. E. , Earle E. D.
Published: January 2018

Anther development of the C‐cytoplasmic male‐sterile (cms C) and the normal cytoplasm version (N) in the W182BN corn inbred was studied by light and electron microscopy. Deviation from normal pollen development was first observed in the tapetal cells at the tetrad stage of development. Two types of tapetal abnormalities were observed in plants with C cytoplasm. The first behaved like the N anther until the tetrad stage, when numerous small vacuoles appeared in the tapetal cells. Inner and radial tapetal cell walls broke down normally, but irregular Ubisch body deposition was observed, and exine development was inhibited and delayed. The tapetum and microspores disintegrated at the intermediate microspore stage. The second type of tapetum was highly vacuolated at the early tetrad stage, with dense inner and radial cell walls that remained intact and enlarged when the tetrads aborted. No organellar abnormalities, such as the mitochondrial changes observed in cms T, were observed in C anthers.
SITE‐SPECIFIC CHANGES IN THE BARK TEXTURE OF QUERCUS FALCATA MICHX. (SOUTHERN RED OAK)
Authors: Glitzenstein Jeff , Harcombe P. A.
Published: January 2018

A method of measuring bark texture is described. This method is used to show that bark roughness in Quercus falcata Michx. (southern red oak) increases from mesic to xeric sites. This change does not appear to be explained by variability in tree size and age, or by changes in the relative abundances of varieties falcata and pagodaefolia. We suggest that it may be due to postulated relationships between bark texture (or the associated property of outer bark thickness) and tree fire resistance, nutrient conservation or susceptibility to pathogens.
VARIATION IN CALLOSE DEPOSITION IN THE LIGULES OF SEVEN SPECIES OF SELAGINELLA
Authors: Jagels Richard , Garner John
Published: January 2018

The deposition of ligular callose, as defined and measured by fluorescence microscopy, was found to vary among different species of Selaginella. Species from dry, sunny habitats possessed greater quantities of callose in leaf ligules than did those species native to wet, shaded habitats.
FINE STRUCTURE OF PARAMOEBIDIUM (TRICHOMYCETES) AND A NEW SPECIES WITH VIRUSLIKE PARTICLES
Authors: Dang Si‐Nan , Lichtwardt Robert W.
Published: January 2018

The amoeba‐cyst cycle of Paramoebidium (Amoebidiales) is described as it develops in the rectum of its larval insect hosts and in the external aquatic environment. Numerous wall channels with associated vesicles aggregated at the apical end of the cystopores may allow rapid extrusion of holdfast material through the wall, in a manner resembling holdfast formation by sporangiospores of Amoebidium parasiticum. It is suggested that the cysts, in addition to their possible resistance to adverse environmental conditions, may function as timing devices to insure establishment of thalli in the proper location in the rectum. A new species is described, P. curvum Lichtwardt, which was found to contain polyhedral viruslike particles scattered in the cytoplasm.
MORPHOMETRY OF ORCHID SEEDS. I. PAPHIOPEDILUM AND NATIVE CALIFORNIA AND RELATED SPECIES OF CYPRIPEDIUM
Authors: Arditti Joseph , Michaud Justine D. , Healey Patrick L.
Published: January 2018

Examination of differences in morphology, size and color between seeds of the genera Paphiopedilum and Cypripedium (family: Orchidaceae; subfamily: Cypripedoideae) and among several Cypripedium species confirm present taxonomic relationships. Additionally, the shape, size and relatively large air volume in the testae (79–96% of available space) provide an explanation for their long flotation periods in the atmosphere, which is an adaptation for dispersal by wind.
CHATTAWAYA (STERCULIACEAE): A NEW GENUS OF WOOD FROM THE EOCENE OF OREGON AND ITS IMPLICATIONS FOR XYLEM EVOLUTION OF THE EXTANT GENUS PTEROSPERMUM
Authors: Manchester Steven R.
Published: January 2018

A new sterculiaceous wood, Chattawaya paliformis gen. et sp. n., was collected from a Middle Eocene locality in the type area of the Clamo Formation of north central Oregon. The wood differs from all known extant woods in having very large and irregularly shaped tile cells. However, other features of the xylem indicate a close natural relationship between Chattawaya and the extant paleotropical genus, Pterospermum. It is suggested that the xylem organization of the Eocene fossil represents a more primitive condition than that observed in Pterospermum. Comparative xylotomy indicates three evolutionary trends within the complex to which Chattawaya and Pterospermum belong: development of storied structure, increased uniformity in shape and size of tile cells and loss of multiseriate rays. Chattawaya is part of a growing body of paleobotanical evidence indicating that the Sterculiaceae was well differentiated by the early Tertiary, but that the lineages leading to extant genera have undergone an appreciable amount of evolutionary change since the Eocene.
SHOOT VASCULAR SYSTEM AND PHYLLOTAXIS OF CASUARINA (CASUARINACEAE)
Authors: Flores Eugenia M.
Published: January 2018

In species of Casuarina with multileaved whorls, each stem vascular bundle divides radially into two at the site of a leaf trace separation, and the same two bundles rejoin acropetally to where the trace supplies a leaf. Such divisions are divisions of a single vascular bundle, and the rejoining of bundles forms a single bundle. Proposals that the extant primary vascular systems of dicotyledons may have been derived as in conifers are incorrect in so far as Casuarina is concerned, or the system has evolved beyond that so far proposed for dicotyledons. Reasons are offered, however, for considering that fernlike leaf gaps are not present. Leaf traces supply leaves at the first nodes distal to their origins. The ways by which an increase or decrease of stem bundles occur are described. Phyllotactic patterns range from helical (rare) to whorled. In the embryo, where leaves occur decussately, of certain species with multileaved whorls, and in the shoot apices of species with tetramerous whorls, slight differences in the levels of leaf attachments and the bending of leaf traces indicate the probable evolution of extant whorled phyllotaxies from one or more helical arrangements. Stages in the evolution are suggested. The leaves in most species with multileaved whorls are in true whorls. The original periderm of branchlets lies internally to the internodal traces and chlorenchyma, but is otherwise external to the vascular system. It is concluded that each leaf originates at its level of separation from the axis despite several structural features suggesting that the leaf bases have become congenitally adnate to the stem.
REPRODUCTION AND VARIATION IN ACONITUM COLUMBIANUM (RANUNCULACEAE), WITH EMPHASIS ON CALIFORNIA POPULATIONS
Authors: Brink Donald E.
Published: January 2018

Nectary depth in Aconitum columbianum Nutt. in T. & G. shows little variation within populations but much continuous variation among populations. Mean nectary depth in populations studied ranges from 3.4 mm (SD = ±0.32) to 9.4 mm (SD = ±0.75). Correlations of nectary depths with the foraging behaviors and tongue lengths of bees visiting A. columbianum flowers indicate that populations with shallow nectaries are adapted to pollination by both short‐ and long‐tongued bees. Bumblebee species with short tongues are not usually pollinators of flowers in populations with deep nectaries. Nectary depth is geographically correlated in California, and populations over large areas have similar nectary depths. Nectary depth is also correlated with bulbifery. Bulbiferous plants have strictly shallow nectaries, and are confined to two regions near the western extreme of the range of A. columbianum. The range of bulbiferous Aconitum in California is contiguous with the range of non‐bulbiferous populations with shallow nectaries.
CYTOGEOGRAPHICAL STUDIES IN THE GENUS ARNICA (COMPOSITAE: SENECIONEAE). I
Authors: Wolf Steven J.
Published: January 2018

A total of 134 chromosome counts representing 21 taxa of the genus Arnica are presented. Counts are published here for the first time for A. lonchophylla (n = 38) and A. nevadensis (n = 38). Ten previously unreported counts representing 9 taxa are also presented. The basic chromosome number of the genus is x = 19. With respect to chromosome number, the genus exhibits maximum diversity in the Rocky Mountains of Colorado and Wyoming. Arnica angustifolia, A. cordifolia and A. mollis are recognized as mature polyploid complexes, containing several wide ranging polyploid races and only a few highly restricted or scattered diploid races. Within the genus in general, diploids tend to be restricted to unglaciated areas while polyploids are much wider ranging, particularly in unglaciated areas.
THE FATE OF VIOLA SEEDS DISPERSED BY ANTS
Authors: Culver David C. , Beattie Andrew J.
Published: January 2018

Experimental plantings of the seeds of the two species Viola odorata and V. hirta were carried out to determine relative importance of three effects of myrmecochory: 1) clumping of seeds, 2) scarification of the testa and elaiosome removal, and 3) relocation into ant nests. The study site was a beech‐larch wood in southern England. Data show that clumping slightly reduces seedling emergence, scarification and elaiosome removal slightly enhances it, while the nest environment significantly increases the rate of seedling emergence. Only the last effect is statistically significant. Seedlings from nests have larger first adult leaves. The possible impact of ant manipulation of seeds on seedling recruitment into myrmecochorous populations is discussed.
GERMINATION AND GROWTH OF CELOSIA CRISTATA L., UNDER VARIOUS LIGHT AND TEMPERATURE REGIMES
Authors: Okusanya Olubukanla T.
Published: January 2018

Continuous light or alternating light and dark appear to be necessary for good germination of Celosia cristata L. As temperature increased up to 31 C so did germination; thereafter, it decreased. There appears to be a preference for high constant or high alternating temperatures in germination. As light intensity decreased so did growth in terms of leaf area, dry weight and relative growth rate. Proportionally more leaf is also made and leaf:area ratio increased. However, root weight ratio decreased. Although both high light intensity and high temperature are required for the good growth of Celosia, temperature appeared to be more important than light. A reduction of less than one‐third of full light may not cause a significant reduction in growth. The results explain the observed differences in the nature of C. cristata in the field as well as its distributional limits.
FLOWERING BEHAVIOR OF THE NEOTROPICAL GENUS ANTHURIUM (ARACEAE)
Authors: Croat Thomas B.
Published: January 2018

The genus Anthurium (Araceae) is one of the most taxonomically complex genera in the neotropics. Studies of living material have shown modes of behavior which probably have a direct influence on pollination biology and evolution. Separation of the sexes is generally accomplished by marked protogyny. Considerable differences also exist in the rate of development of flowers, the presence, source and amount of stigmatic nectar, as well as the method of pollen presentation. The genus exhibits an unusual pattern of staminal emergence. In all species studied, the lateral pair of stamens are first to emerge, usually one at a time, followed by the anterior, then the posterior stamens of the alternate pair. There are also differences in the degree of exsertion, the disposition with respect to the stigma, degree of retraction and changes in pollen color. Some species have stamens which are retracted completely after opening: others have stamens which scarcely emerge but instead force the pollen out in long ribbons. Important differences also exist in flower aromas with both fly and bee pollination syndromes exhibited. All of these aspects of flowering behavior are natural phenomena believed to be important in pollination biology.
MICROSPOROCYTE GROWTH AND MEIOSIS IN PHYLLOSPADIX TORREYI, A MARINE MONOCOTYLEDON
Authors: Stewart J. G. , Rüdenberg L.
Published: January 2018

In this paper we demonstrate spindle rotation during meiosis in filiform microsporocytes of a dioecious marine monocotyledon.

Extensive populations of Phyllospadix torreyi, a seagrass, cover intertidal and shallow subtidal rocks in southern California. Flowering plants are unevenly distributed, being found only in patches within these beds, and apparently are disproportionally few relative to plants that do not produce flowers. Reduction division in male flowers occurs in an already elongate microsporocyte (pollen mother cell), where the chromosomes at metaphase lie in a plane across the narrow axis of the filamentous cell. However, the poles and spindles then rotate through 90° during anaphase of first and second meiotic divisions so that the cells divide longitudinally to produce tetrads which develop into filamentous pollen. Nine bivalents were counted in diakinesis figures. The presence of a heteropycnotic X‐chromosome in male flowers is suggested by certain observations of prophase‐anaphase figures.
TAXONOMY OF ZEA (GRAMINEAE). I. A SUBGENERIC CLASSIFICATION WITH KEY TO TAXA
Authors: Doebley John F. , Iltis Hugh H.
Published: January 2018

The genus Zea is here divided into the Sect. Luxuriantes Doebley & litis sect. n., including the perennials Z. diploperennis (2n = 20) and Z. perennis (2n = 40) and the annual Z. luxurians (2n = 20); and Sect. Zea, including the wild Z. mays ssp.parviglumis and Z. mays ssp. mexicana (both 2n = 20), and Z. mays ssp. mays (2n = 20), the highly domesticated and tremendously variable derivate of the latter. This division is verified by a multivariate analysis of a large number of morphological characters of the male inflorescence. Cytogenetic and chemotaxonomic evidence supports the morphological conclusions. A consideration of the phylogeny of Zea within the conceptual framework offered by this new sectioning of the genus points convincingly to annual teosinte (Z. mays ssp. mexicana) as the ancestor of cultivated maize.
CHROMOSOME NUMBERS AND SATELLITE CHROMOSOME MORPHOLOGY IN ASTER AND LASALLEA
Authors: Semple John C. , Brouillet Luc
Published: January 2018

Chromosome numbers were determined from more than 241 populations of 46 species and five interspecific hybrids of Aster L. (X = 9, 8, 7) and from 48 populations of nine species and one interspecific hybrid of the redefined genus Lasallea Greene (X = 5). Seventeen first reports are listed for Aster and four for Lasallea. The Nucleolar Organizer Region chromosome of the species of Aster examined had a satellite either equal to or longer than the short arm region, while all nine species of Lasallea had a very small satellite. The retention of the species of subg. Oxytripolium (X = 5) in Aster was found questionable on cytological grounds, and it was done so for nomenclatural reasons only.
POPULATION VARIATION AND HYBRIDIZATION IN SEA‐ROCKETS (CAKILE, CRUCIFERAE): SEED GLUCOSINOLATE CHARACTERS
Authors: Rodman James Eric
Published: January 2018

In a study of intra‐ and interpopulation variation in seed glucosinolates, remarkable uniformity was found among individuals within the two chemically distinct subspecies of East Coast Cakile edentula. Glucosinolates were used as taxonomic markers in a study of hybridization between ssp. edentula and ssp. harperi where they form mixed populations on the Outer Banks of North Carolina. Thirteen plants with hybrid chemical profiles were detected in a sample of 89 individuals from four populations; the zone of hybridization is narrow, and has persisted for at least eight years. Artificial hybrids of the two subspecies are additive for kinds and intermediate for proportions of seed glucosinolates, and families of F2's show a range of recombinant chemical profiles. Natural hybridization was confirmed by recovering hybrid and parental types in 47 progeny of three presumptive wild hybrids. Glucosinolate profile characteristics segregated independently of the segregation patterns for fruit length and seed weight. Selection against particular glucosinolate phenotypes is one possible mechanism maintaining this narrow hybrid zone on the Outer Banks.
AUTOGAMOUS ALLOHOMOPLOIDY IN ALSOPHILA AND NEPHELEA (CYATHEACEAE): A NEW HYPOTHESIS FOR SPECIATION IN HOMOPLOID HOMOSPOROUS FERNS
Authors: Conant David S. , Cooper‐Driver Gillian
Published: January 2018

Morphological and chemosystematic studies demonstrate that three endemic Puerto Rican tree ferns, Alsophila bryophila, A. dryopteroides and Nephelea portoricensis have been hybridizing and have produced a hybrid swarm. Three distinct hybrids are present, one of which is strikingly uniform in its morphology. The population ecology of species and hybrids indicates that the most uniform hybrid is more abundant and has a narrower ecological adaptation than its parents. The hybrids are fertile diploids and are producing F2 segregates which resemble species from other islands in the Greater Antilles. An hypothesis for the stabilization of hybrid reproduction at the homoploid level, autogamous allohomoploidy, is proposed. The hypothesis explains the sharing of unique characters between sympatric species pairs of Alsophila and Nephelea in the Greater Antilles and in Central and South America. It is suggested that other genera of homosporous ferns have also speciated by autogamous allohomoploidy.
PARALYCOPODITES MOREY & MOREY, FROM THE CARBONIFEROUS OF EURAMERICA—A REASSESSMENT OF GENERIC AFFINITIES AND EVOLUTION OF “LEPIDODENDRON” BREVIFOLIUM WILLIAMSON
Authors: DiMichele William A.
Published: January 2018

A study of the morphologies and evolutionary relationships of Upper Carboniferous coal swamp lycopods indicated that plants traditionally treated as Lepidodendron hrevifolium were distinct from Lepidodendron at the generic level, and were not part of a morphological cline between Lepidodendron and Lepidophloios. The description of a new genus and species by Morey and Morey (1977), based on a specimen identical to L. brevifolium distal branches, results in the inclusions of L. brevifolium in Paralycopodites, in which it has nomenclatural priority over P. minutissimus. The small trees or shrubs had deciduous lateral branches and permanently retained leaves; in these characters, Paralycopodites is most similar to the compression‐impression genus Ulodendron as delimited by Thomas. Bisporangiate Lepidostrobus cones are closely associated with the vegetative remains; the cones can be assigned to three stratigraphically complementary species throughout the range of Paralycopodites—Visean to Westphalian D (Middle Pennsylvanian). Extreme evolutionary conservatism is indicated by the low vegetative morphological variability and the great similarities in morphology of associated cones; in combination with the sudden Visean appearance of P. brevifolius and the lack of intermediates among major lycopod genera, this lends support to punctuated equilibria hypotheses. Paralycopodites was generally rare in coal swamps, possibly related to its production of megaspores lacking specialized adaptations for flotation. Its pattern of late Middle Pennsylvanian extinction parallels Lepidodendron and Lepidophloios.
ULTRASTRUCTURE OF THE DINOFLAGELLATE PERIDINIUM CINCTUM F. OVOPLANUM. II. LIGHT AND ELECTRON MICROSCOPIC OBSERVATIONS ON FERTILIZATION
Authors: Spector D. L. , Pfiester L. A. , Triemer R. E.
Published: January 2018

Fertilization inPeridinium cinctumf.ovoplamtmhas been investigated at both the light and electron microscopic levels. Gamete formation occurs when vegetative cells are placed into nitrogen deficient media. The majority of gametes observed possess thin thecal plates; however, some are naked. Gametes have few chloroplasts as compared to vegetative cells, numerous membrane bounded storage bodies, many starch grains, and chromosomes which appear slightly unwound. Gamete fusion is observed to peak 7–10 days after inoculation into nitrogen deficient media. Fusion occurs in an area of the sulcus devoid of reticulate thecal plates at or adjacent to the flagellar pores. A fertilization tube is formed and proceeds to widen along the sulcus. Karyogamy occurs within the fertilization tube before plasmogamy is completed. The resulting planozygote is a two walled structure containing two longitudinal flagella. It enlarges over a 2‐week period giving rise to the hypnozygote.
CRYSTALLOGRAPHY OF THE TWO HYDRATES OF CRYSTALLINE CALCIUM OXALATE IN PLANTS
Authors: Frey‐Wyssling Albert
Published: January 2018

Crystal forms and crystal structure of the metastable polyhydrate (weddellite) and the stable monohydrate (whewellite) occurring in plant cells are described and their formation as well as their physiological bearing are discussed.
NUCLEAR MIGRATION AND ASYMMETRIC CELL DIVISION IN ONOCLEA SENSIBILIS SPORES: AN ULTRASTRUCTURAL AND CYTOCHEMICAL STUDY
Authors: Bassel Alix R. , Kuehnert Charles Carroll , Miller John H.
Published: January 2018

A method of preparation for electron microscopy of fern spores in early stages of germination is presented. The cytochemistry and fine structure of Onoclea spores during the early stages of germination are described. The cytoplasm of the hydrated spore is filled with lipid droplets, protein granules and chloroplasts. During the early stages of development ribosomes and mitochondria increase in the area surrounding the central nucleus, and a new peripheral wall forms around the protoplast. Microtubules and large, branching mitochondria are associated with the nucleus during migration from its original central position in the spore to the proximal face and then to one end of the spore. There is no morphological polarization of cytoplasmic organelles of the spore before migration of the nucleus.
ZOOSPORE STRUCTURE OF THE MYCOPARASITIC CHYTRID CAULOCHYTRIUM PROTOSTELIOIDES OLIVE
Authors: Powell Martha J.
Published: January 2018

The subcellular organization of zoospores released from sessile, parasitic sporangia ofCaulochytrium protostelioideswas studied with light and electron microscopy. A single flagellum is posteriorly directed but laterally inserted into the cylindrical motile zoospore. A striated rhizoplast attaches the proximal end of the kinetosome to a specialized region of the nuclear envelope. A system of rough endoplasmic reticulum, smooth endoplasmic reticulum, dictyosomes and bristle‐coated vesicles are associated with the one to several pulsating vacuoles typically located near the flagellar apparatus. The microbody‐lipid globule complex (MLC) comprises one to many lipid globules. An extensive microbody branches around each lipid globule and encloses a portion of the rhizoplast. A reticulum of smooth surfaced cisternae interdigitates among the branches of the complex microbody, and cisternae are opposed to the surface of lipid globules opposite the microbodies. Mitochondria with predominantly circular profiles are scattered throughout the zoospore body, but several are always adjacent to the microbody, and hence, are also part of the MLC. Ribosomes are uniformly distributed throughout the zoospore, and one to several cisternae of rough endoplasmic reticulum are adjacent to the nuclear envelope. Zoospores ofC. protostelioidesare similar to several other chytrid zoospores, which also have the same type of microbody‐lipid globule complex, but yet are structurally distinct from any other chytrid zoospore.
OBSERVATIONS ON PTYXIS, PHENOLOGY, AND TRICHOMES IN THE CYCADALES AND THEIR SYSTEMATIC IMPLICATIONS
Authors: Stevenson Dennis Wm.
Published: January 2018

Ptyxis, phenology, and leaf trichomes are described for 43 species representing all ten genera in the Cycadales. The typical annual growth sequence is: leaf flush production, cataphyll production, reproductive production, and finally cataphyll production in all taxa except Stangeria which does not have cataphylls and produces leaves one at a time throughout the year. The leaf and cataphyll bases are slightly winged except in Zamia and Ceratozamia, which have well developed stipules, and in Stangeria, which has a distinctive adaxial, stipular hood on the leaf bases. Longitudinal ptyxis of the whole leaf is of four types: circinate (only in Bowenia); erect (Cycas, Dioon, Encephalartos, Lepidozamia, Macrozamia, Microcycas, and some Zamia spp.); inflexed (Stangeria, Ceratozamia, and some Zamia spp.); and reflexed (rarely found in Cycas and Dioon). The pinnae are oriented so that the horizontal ptyxis is conduplicate in all taxa except Bowenia and Cycas where it is involute. The individual pinnae are circinate in Bowenia and Cycas, conduplicate in Stangeria, and flat in all other taxa. The pinnules of Bowenia are also flat. Leaf trichomes are of six types: transparent unbranched; transparent branched; colored unbranched; colored branched; colored idioblastic; and short colored curved. Cycas has only transparent branched (unequally) and unbranched. Ceratozamia, Dioon, Encephalartos, and Stangeria have transparent and colored trichomes, both unbranched. Bowenia, Lepidozamia and Macrozamia have short colored curved hairs and transparent unbranched hairs. Macrozamia is the only taxon with colored idioblastic trichomes. Zamia and Microcycas have transparent and colored hairs. Both trichome types occur branched and unbranched. Because of its decompound leaf, circinate ptyxis, cones on short determinate branches and other distinct characters the family Boweniaceae D. Stevenson fam. nov. is described. This family contains one genus: Bowenia.
CHANGES IN EPILOBIUM PHYLLOTAXY INDUCED BY N‐1‐NAPHTHYLPHTHALAMIC ACID AND α‐4‐CHLOROPHENOXYISOBUTYRIC ACID
Authors: Meicenheimer Roger D.
Published: January 2018

Preliminary studies establishing relationships between leaf plastochron index and Epilobium hirsutum L. shoot growth provide a method for rigorous selection of plants utilized in experiments designed to test the working hypothesis that endogenous auxin gradient interactions are factors of phyllotactic control in this species. Application of N‐1‐naphthylphthalamic acid (NPA), an auxin transport inhibitor, to one of the youngest bijugate primordia on the shoot meristem results in increased growth of the treated primordium. Fasciation between the treated primordium and one of the next primordia to be initiated alters relative vertical spacing of primordia. Angular shifts between subsequent primordia result in spiral transformation of Epilobium bijugate phyllotaxy. Application of α‐4‐chlorophenoxyisobutyric acid (CPIB), an auxin antagonist, to one of the youngest bijugate primordia on the shoot meristem results in decreased growth of the treated primordium that alters both radial and vertical spacing of primordia. This is followed by angular shifts between subsequent primordia resulting in spiral transformation of the bijugate phyllotaxy. Changes in the growth parameters of NPA‐ and CPIB‐treated shoots are similar. Relative plastochron rates of radial and vertical shoot growth of induced spiral shoots are about half those of lanolin paste control shoots, as are the plastochrons and relative plastochron rates of leaf elongation. Treated shoot meristems have eccentricities of 0.5 as compared to bijugate control meristem eccentricities of 0.7. No significant difference is apparent between basal transverse areas of treated and control shoot meristems. The relative chronological rates of growth of treated shoots are not significantly different from those rates of control shoots. Spiral transformation results from changes in relative positions of leaf primordia insertion on the shoot meristem, not from changes in growth of treated shoots. These changes are accompanied by an increased rate of leaf initiation on a more circular shoot meristem. Existing theoretical models of phyllotaxy are discussed in relation to these chemically induced changes of Epilobium leaf arrangement.
MITOTIC ACTIVITY IN THE ROOT APEX OF THE WATER FERN MARSILEA VESTITA HOOK. AND GREV.
Authors: Kurth Eva
Published: January 2018

Roots of Marsilea vestita ranging from 1–120 mm in length, as well as root primordia, were analyzed to determine mitotic activity and ploidy levels in the apical cell, five well‐defined regions of the root proper, and two regions in the root cap. The mitotic index of the apical cell tended to be above the overall mean mitotic index for the entire apical meristem. No diurnal rhythm in mitotic index was apparent. The cell‐cycle duration of the apical cell ranged from 12.1–25.2 hr, that of other regions of the root from 16.1–41.5 hr. There was no indication of polyploidy in any part of the apical meristem except in a few procambial cells. Thus, the results support the classical concept that the apical cell is the ultimate source of cells in the root.
MORE EVIDENCE FOR CONIFER DIVERSITY IN THE UPPER TRIASSIC OF NORTH CAROLINA
Authors: Delevoryas T. , Hope R. C.
Published: January 2018

An ovulate strobilus from the Upper Triassic Deep River Basin, North Carolina, has helically arranged, loosely aggregated, elongated, spatulate bracts with axillary ovule‐bearing appendages with about 8–10 ovules attached in two lateral rows, with outwardly directed micropyles. The axillary ovuliferous appendage is homologous with the voltzialean fertile dwarf shoot, but probably not directly evolved from it. More credible is a suggested origin from a completely fertile axillary appendage such as that of the Lower Permian Trichopitys. The occurrence of this cone, Metridiostrobus palissyaeoides, gen. and sp. nov., along with Compsostrobus neotericus and Voltzia andrewsii, reflects considerable diversity among conifer ovulate cones during the Upper Triassic.
THE BALANCE OF FORCES GENERATED BY THE WATER POTENTIAL IN THE CELL‐WALL‐MATRIX—A MODEL
Authors: McClendon John H.
Published: January 2018

A cell in contact with air is considered. The nature of the water within a cell wall is assumed (with citations in support) to be that of free water and essentially free of diffusible solutes, so that the air‐water interface generates negative pressures (Pf) (at all relative humidities less than 100%), equal to the overall cell‐water‐potential. At the inner wall‐surface, the turgor pressure (Pt) is balanced by the sum of Pf and a pressure resisting collapse of the wall matrix (Psi); at the outer wall‐surface, Pf is balanced only by a similar pressure (Pso). Under all circumstances, Psi = Pt – Pf, and the osmotic term of the internal cell‐water‐potential (Ψis) = –Psi. At full turgor, Pso is zero, and it rises as water is lost, equalling Psi when Pt is zero (Psi = –Pf).

In cells in contact with solutions of solutes which penetrate the wall, Pf and Pso are zero and Psi follows Pt.

In either case, the hoop stress, tending to enlarge the cell surface, is proportional to Pt, but the cell‐in‐contact‐with‐air has radial stresses not found in submerged cells.

The nature of the forces resisting radial compression of the wall is discussed, and thought to be a combination of mechanical elastic forces and osmotic forces due to non‐diffusible polysaccharides of the wall.
SVALBARDIA BANKSII SP. NOV. FROM THE UPPER DEVONIAN (FRASNIAN) OF NEW YORK STATE
Authors: Matten Lawrence C.
Published: January 2018

Svalbardia banksii sp. nov., is described from the Upper Devonian (Frasnian) Fish Cabin Creek locality near Pond Eddy, New York. The compression consists of ultimate branches bearing spirally arranged, unwebbed leaves. The unwebbed leaves are up to 3.2 cm long, are somewhat flexuous, and dichotomize in more than one plane. The new species is similar to the reconstruction of Actinoxylon banksii from the Middle Devonian (Givetian) of New York and strengthens the supposed relationship between Svalbardia polymorpha and Actinopodium nathorstii from Mimerdalen, Spitzbergen.
INTERGENERIC HYBRIDIZATION, INDUCED POLYPLOIDY, AND THE ORIGIN OF THE HAWAIIAN ENDEMIC LIPOCHAETA FROM WEDELIA (COMPOSITAE)
Authors: Rabakonandrianina Elisabeth , Carr Gerald D.
Published: January 2018

The genetic relationships of the Hawaiian endemic genus Lipochaeta and the nearly cosmopolitan but extra‐Hawaiian genus Wedelia were assessed by way of experimental hybridization. Hybrids between Wedelia biflora and diploid species of Lipochaeta consistently exhibited 15 pairs of chromosomes at meiosis, whereas the modal and maximum configuration seen in hybrids between W. biflora and tetraploid species of Lipochaeta was 15II + 11I. Meiotic pairing in microsporocytes of the intergeneric hybrid combinations involving Wedelia trilobata and both sections of Lipochaeta is lower than in intergeneric hybrids involving W. biflora. All of the intergeneric F, hybrids produced had relatively low pollen stainabilities ranging from less than 1–16% and, although they were vegetatively vigorous, they failed to produce viable achenes. The effects of chromosome doubling by colchicine in one species and several hybrids in Lipochaeta and in one intergeneric hybrid between Lipochaeta and Wedelia were studied. Chromosome doubling of the diploid species caused a decrease in pollen stainability and resulted in lack of achene production, whereas doubling the chromosomes of sterile intersectional and intergeneric hybrids restored female fertility and effected a dramatic increase in pollen stainability. Cytological analysis of the microsporocytes at diakinesis and metaphase I revealed pairs and quadrivalents in the induced polyploids. Pollen measurements indicated that pollen size in Lipochaeta is correlated with doubling of the chromosomes. Statistical analyses revealed that there is no significant difference in pollen size between the diploids and natural tetraploids, whereas both groups have pollen grains that are significantly smaller than the induced autotetraploid, the intergeneric allotetraploid, and the intersectional allohexaploid. The cytogenetic evidence indicates a relatively close genetic relationship between Wedelia and Lipochaeta and supports the view that the ancestry of the diploid section Aphanopappus of Lipochaeta (n = 15) is to be found in a species akin to Wedelia biflora (n = 15) and that this or a similar 15‐paired wedelioid species and an unknown 11‐paired wedelioid taxon are involved in the alloploid hybrid origin of the tetraploid section Lipochaeta (n = 26) of Lipochaeta.
SYSTEMATICS OF SOUTH AMERICAN TRIPSACUM (GRAMINEAE)
Authors: de Wet J. M. J. , Timothy D. H. , Hilu K. W. , Fletcher G. B.
Published: January 2018

The genus Tripsacum is widely distributed between 42°N and 24°S latitude. In South America, the genus extends around the Amazon and Orinoco basin, and from the Caribbean coast south to Brazil and Paraguay. The most common South American taxon is T. dactyloides (L.) L. var. meridonale de Wet and Timothy (2n = 36), which differs from North American representatives of the species in having subdigitate recemes usually appressed with the apical male sections typically curved. Closely related to T. dactyloides, but usually occupying more seasonally moist and dry habitats, is T. australe Cutler and Anderson. This species is typically robust with the basal leaf sheaths tomentose, and the much elongated culms becoming decumbent in older plants. Smaller plants, with essentially erect culms and leaf sheaths on the culms hirsute rather than tomentose, are recognized as T. australe var. hirsutum de Wet and Timothy. The two varieties of T. australe are both diploid (2n = 36) and they cross to produce fertile hybrids. They also cross with T. dactyloides var. meridonale (2n = 36), but these hybrids are partially sterile. Tripsacum cundinamarce de Wet and Timothy (2n = 36) is a robust species with glaucus leaves. It resembles robust specimens of T. dactyloides in having glabrous leaf sheaths, but can always be recognized by inflorescences that are composed of racemes arranged along a several‐noded primary axis. This species is confined to moist habitats, while T. dactyloides occupies a range of habitats in South America. Tripsacum peruvianum de Wet and Timothy is a gametophytic apomict with 2n = 72, 90 or 108 chromosomes. It is characterized by an erect growth habit and strongly hirsute leaf sheaths. The cultivated Guatemala grass, T. andersonii Gray, occurs spontaneously in the mountains of Venezuela, Colombia, and Peru. This sexually sterile species is characterized by 2n = 64, and may combine 54 Tripsacum and 10 Zea chromosomes in its genome. Electrophoretic patterns of seed storage proteins confirm the validity of recognizing T. cundinamarce as distinct from T. dactyloides, and T. peruvianum as distinct from T. australe.
POLLEN MORPHOLOGY AND ULTRASTRUCTURE OF KRAMERIA (KRAMERIACEAE): UTILITY IN QUESTIONS OF INTRAFAMILIAL AND INTERFAMILIAL CLASSIFICATION
Authors: Simpson B. B. , Skvarla J. J.
Published: January 2018

The genus Krameria is currently recognized as an enigmatic, monotypic family of dicotyledons. Previous studies of morphology, anatomy, and cytology have been unable to establish unequivocably its phyletic affinities. We report here the results of an intensive investigation of the pollen of Krameria using light, scanning electron (SEM), and transmission electron microscopy (TEM). Pollen characteristics of the genus were compared to those of all families referred to the Polygalales and to selected species of the Leguminosae‐Caesalpinoideae, both groups with which Krameria has historically been allied. Superficially, the pollen of Krameria resembles that of the legumes more than that of genera in the Polygalales. However, in ultrastructure, it differs from the pollen of all taxa investigated from both groups. Within Krameria, several variations of a basic type of 3‐colporate pollen are discernible. Species with similar pollen variants appear, on the basis of other morphological data, to represent natural groups within the genus. Nevertheless, an arrangement of groups of species of Krameria from “least” to “most” specialized, based on a logical sequence of modification of the pollen morphology, does not agree with any sequence of specialization using other morphological or ecological characters. It is concluded that pollen morphology and ultrastructure has systematic value for intrafamilial groupings of the Krameriaceae but that palynological modifications are incongruous with trends of specializations of other characters and, like many other lines of investigation, pollen studies do not provide significant data as to the phylogenetic affinities of the family.
FUNCTION OF MENTZELIA NUDA (LOASACEAE) POSTFLORAL NECTARIES IN SEED DEFENSE
Authors: Keeler Kathleen H.
Published: January 2018

Mentzelia nuda is a coarse, short‐lived perennial of the High Plains of North America. The flowers secrete nectar which serves as an attractant for pollinating bees. Postfloral nectar secretion attracts ants whose presence significantly enhances seed set. This is the first demonstration of advantage to postflowering activity of a floral nectary.
AIRFLOW PATTERNS AROUND SOME EARLY SEED PLANT OVULES AND CUPULES: IMPLICATIONS CONCERNING EFFICIENCY IN WIND POLLINATION
Authors: Niklas Karl J.
Published: January 2018

Aerodynamic analyses showing characteristic airflow patterns and the potential for wind‐mediated pollination are presented for models of Paleozoic (Carboniferous) ovules and ovulate cupules (i.e., Genomosperma kidstoni, G. latens, Salpingostoma dasu, Physostoma elegans, Eurystoma angulare, and Stamnostoma huttonense). Lobes on ovules and cupules are shown to produce localized regions of turbulent flow with a concomitant reduction in airflow velocity. Data based upon models that mimic the characteristics of windborne pollen (= pseudopollen) show that these regions of turbulent flow correspond to those in which suspended pseudopollen impact with ovule and/or cupule surfaces. These data have bearing on a sequence of ovule morphologies purported to show the evolution of the integument by the progressive reduction in length of “preintegumentary” lobes and their acropetal fusion. As the preintegumentary lobes of the models studied consolidate around the megasporangium, regions of turbulent flow and high pseudopollen impact become localized around the pollen chamber or salpinx. The general morphologic trend envisioned for the evolution of the ovule is seen to be associated with an aerodynamic streamlining and an increased potential for wind‐mediated pollination. Data for hair‐bearing ovules and for ovulate cupules are discussed within the context of possible selective pressures favouring streamlining.
THE FLORAL MORPHOLOGY OF ASCLEPIAS SPECIOSA (ASCLEPIADACEAE) IN RELATION TO POLLINATION AND A CLARIFICATION IN TERMINOLOGY FOR THE GENUS
Authors: Bookman Susan Stone
Published: January 2018

The profusion of terms for floral parts inAsclepiasis summarized in tabular form to clarify previous literature. In cases of synonymy, a preferred term is selected. These terms are then used in an illustrated description of the floral morphology and pollination mechanism of a representative species,Asclepias speciosa.
COMPARATIVE PALEOBIOCHEMISTRY OF SOME FOSSIL AND EXTANT FAGACEAE
Authors: Giannasi David E. , Niklas Karl J.
Published: January 2018

A Fagus‐like leaf fossil (cuticular compression) with an attached fruit, differing from any known Fagus species (fossil or extant) or other fagoid taxa, has been discovered from the Miocene Clarkia Lake deposits of northern Idaho. Because of its unusual morphology (especially the fruit) the fossil taxon has been described as a new genus and species, Pseudofagus idahoensis Smiley and Huggins. The successful previous use of paleobiochemistry in studies of fossil taxa from the Miocene Succor Creek Flora of Oregon suggested that chemical data might help clarify the taxonomic affinities of Pseudofagus. Indeed, examination of the chemistry of the fossil, Pseudofagus idahoensis, and comparison with extant Fagus species and related fagoid genera indicate that: 1) based on steroid chemistry, Pseudofagus idahonesis does belong in the Fagaceae; 2) like all extant species of Fagus, the fossil lacks the tannin component, ellagic acid, which separates it from other extant fagoid genera, and 3) its simple flavonoid pigment profile places it closest to the extant North American Fagus grandifolia or the European/Eurasian Fagus sylvatica. However, the exclusive presence of an isorhamnetin (3'‐methoxyquercetin) 3‐0‐glycoside, onocerane, and 5α‐cholestane imparts a species‐specific chemical character to Pseudofagus idahoensis, which also sets it apart from extant species of Fagus. While the chemistry does not decide the taxonomic level to be accorded to the fossil, it certainly supports, along with morphology and anatomy, the distinctness of Pseudofagus and its proposed relationships within the Fagaceae.
SPATIAL PATTERNING AND COMPETITION IN AN ASPEN‐WHITE PINE SUCCESSIONAL SYSTEM
Authors: Squiers Edwin R. , Klosterman Jane E.
Published: January 2018

The spatial patterning of and competition between established large‐toothed aspen (Populus grandidentata) and invading white pine (Pinus strobus) were examined in a 65‐yr‐old forest system at the AuSable Trails Institute of Environmental Studies, Kalkaska County, Michigan. Density, diameter, and distance measures were recorded for tree species on two 40 × 40 m grids containing 64 quadrats each 5 × 5 m. Several indices of dispersion were used to assess pattern and regression analysis of nearest neighbor distance to tree diameter provided an index of competition. The results indicate strong aggregation for both aspen and pine on a large scale, but regularity of pattern for pines in relation to their nearest neighbor. This regularity appears to be due to competition with established aspens and suggests that the spatial patterning of the aspens acts to control the spacing and subsequent development of the invading white pines.
SPORE MORPHOLOGY IN THE DICKSONIACEAE. I. THE GENERA CYSTODIUM, THYRSOPTERIS, AND CULCITA
Authors: Gastony Gerald J.
Published: January 2018

The most mature spores available in herbarium specimens of the dicksoniaceous genera Cystodium, Thyrsopteris, and Culcita were studied by scanning electron microscopy and light microscopy, and representative specimens were analyzed to determine the number of spores produced per sporangium. Thyrsopteris and Culcita feature 64‐spored sporangia, but Cystodium is consistently 32‐spored. Spores were analyzed both in their native state as found on the specimens and in a perine‐free state achieved by treatment with sodium hydroxide or acetolysis mixture. The sodium hydroxide assay demonstrated the presence of a perine in Cystodium, Thyrsopteris, and Culcita subgenus Culcita, but no evidence of a perine so defined was found in Culcita subgenus Calochlaena. Spores of Cystodium feature a nearly psilate exine overlain by a striate inner perine and a granular outer perine and are in several respects similar to those of Metaxya in the cyatheoid‐dicksonioid complex and to those of Saccoloma in the dennstaedtioids. The most mature Thyrsopteris spores available may not have been fully mature. They feature a sparsely distributed, granular perinous layer over a microverrucate sculptine. The latter topography is taken as largely perinous since treatment with sodium hydroxide left a nearly psilate exine. The spore morphologies of Cystodium and Thyrsopteris reinforce the taxonomic distinctness of these monotypic genera indicated by their other characters. The two subgenera of Culcita are very dissimilar in their spore morphologies. The exine in subgenus Culcita ranges from psilate to slightly microverrucate proximally and distally, with varying margo development. Spores of subgenus Calochlaena are strongly differentiated from those of subgenus Culcita by their exine of broad spinules which vary in their degree of lateral fusion to each other and in the granular appearance of their distal surfaces. Spore morphology in Culcita strongly supports the argument of those who would raise its subgenera to generic rank.
COMPONENTS OF REPRODUCTIVE EFFORT AND YIELD IN GOLDENRODS
Authors: Primack Richard B. , Rittenhouse Ann R. , August Peter V.
Published: January 2018

Four components of reproductive yield (the weight of reproductive tissue) were examined in relation to their effect on reproductive effort and their relative contributions to reproductive yield in five species of goldenrods (Solidago, Compositae). The yield components were number of flowing stems per plant, number of flowering branches per stem, number of flowering heads per branch, and number of seeds per seed head. Individuals within populations increase their reproductive effort by increasing their reproductive weight, not by decreasing their vegetative weight. Each species shows a different pattern of positive correlations of yield components with reproductive yield and reproductive effort, indicating that each species has its own mechanisms for regulating reproduction. The yield components were not significantly intercorrelated.
SEM SURVEY OF POLLEN MORPHOLOGY AND CLASSIFICATION IN HYDROPHYLLACEAE (WATERLEAF FAMILY)
Authors: Constance Lincoln , Chuang Tsan Iang
Published: January 2018

A general survey of pollen morphology in Hydrophyllaceae, using scanning electron microscopy, is presented. Hydrophyllaceous pollen grains are relatively homogeneous, tricolpate or tricolporate, and with a tectate‐perforate to semitectate exine structure. Surface ornamentation is basically reticulate, but varies sufficiently from genus to genus, and sometimes from species to species, to permit interesting comparisons, but not to draw profound phylogenetic conclusions.