bluuebunny/crossref_metadata_2025 huggingface dataset:
POLLINATION BIOLOGY OF LISTERA CORDATA (ORCHIDACEAE)
Authors: Ackerman James D. , Mesler Michael R.
Published: January 2018

Pollination biology of northern California populations of Listera cordata (L.) R. Br. is presented. The flowers are allogamous, self‐compatible, and protandrous. At anthesis, access to the stigma is blocked by the flap‐like rostellum. When an insect contacts the touch‐sensitive trigger hairs of the rostellum, the pollinia are suddenly released and become cemented to the insect's body. One to two days after the pollinia are removed, the rostellum rises and exposes the receptive stigma. Visitors are attracted to the flowers by their foul odor and minute quantities of nectar presented on the surface of the labellum. Pollination efficiency is high with 61–78% of flowers from several localities setting fruit. The most important and abundant pollinators of L. cordata at our study sites are fungus gnats (Sciaridae and Mycetophylidae). Other less frequently encountered pollinators are members of these families: Braconidae, Ichneumonidae, and Tipulidae. At present, there is no compelling evidence that the floral characteristics of L. cordata have evolved as a result of an evolutionary interaction with any specific group of insects. Nor is there any indication that the flowers are sapromyophilous, despite their putrid odor.
PHYTOTOXICITY OF FUNGICIDES AND BACTERICIDES IN ORCHID CULTURE MEDIA
Authors: Thurston Katherine C. , Spencer Sharon J. , Arditti Joseph
Published: January 2018

A number of fungicides, bactericides and dual‐action substances were screened for phytotoxicity in vitro using Cattleya aurantiaca and Stanhopea occulata (Orchidaceae) seedlings. Of the 25 compounds screened, ten (each at only one concentration) were employed in nine different combinations for nonsterile in vitro cultures of Cattleya aurantiaca seedlings: Amphotericin B, 10 ppm; Benlate, 50 ppm; Dowicide, 5 ppm; Ethirimol, 50 ppm; Gentamicin, 50 ppm; Nystatin, 25 ppm; PCNB, 100 ppm; Penicillin G, 100 ppm; Sodium omadine, 5 ppm; and Vancomycin, 50 ppm. All nine combinations prevented contamination, but had different effects on seedling development.
CONSTANCY OF RELATIVE VOLUMES OF ZONES IN SHOOT APICAL MERISTEMS IN CACTACEAE: IMPLICATIONS CONCERNING MERISTEM SIZE, SHAPE, AND METABOLISM
Authors: Mauseth James D. , Niklas Karl J.
Published: January 2018

The volumes and dimensions of shoot apical meristem zones were determined for 21 species in 10 genera of the Cactaceae. If the volumes of the central‐mother‐cell zone (CMCZ), the peripheral zone (PZ), and the pith‐rib meristem (PRM) are expressed as percentages of the total volume of the corpus, then they are remarkably constant (CMCZ = 11.1% of the volume of the corpus, PZ = 61.2% and PRM = 27.1%) regardless of the relative size of the apical meristems. The relative volume of the tunica decreases, however, as the whole apex increases. The zones have variable shapes, and whereas the PZ and PRM are always trapezoidal in longitudinal section, in apices with large volumes, these zones have a flatter, more flaring shape than they have in smaller apices. Thus large apices are flatter and less hemispherical than are small apices. The CMCZ, however, maintains a constant shape and is always relatively hemispherical regardless of its volume. A hypothesis that relates all of these shape and volume relationships as an integrated growth sequence is proposed.
MORPHOLOGY AND DISTRIBUTION OF PETIOLAR NECTARIES IN IPOMOEA (CONVOLVULACEAE)
Authors: Keeler Kathleen H. , Kaul Robert B.
Published: January 2018

The distribution of petiolar nectaries in 24 species ofIpomoeawas investigated. Petiolar nectaries were found on 12 species (8 new reports, 4 confirmations of previous reports) and quoted from the literature as being found on 3 other species; they were absent from 9 species investigated. The structure of petiolar nectaries in the genus ranges from simple beds of superficial nectar‐secreting trichomes (1 species), to slightly recessed “basin nectaries” (8 species), to “crypt nectaries,” which are structurally the most complex extrafloral nectaries known (3 species). (Structures were not determined for 3 species.) Petiolar nectaries are present in all subgenera, but all crypt nectaries occur in the same section(Eriospermum). Species with extrafloral nectaries tend to be perennial; species lacking extrafloral nectaries tend to be annual. There is no relationship between temperate or tropical habitat and presence of nectaries.
ULTRASTRUCTURE OF NECTARIES IN RELATION TO NECTAR SECRETION
Authors: Fahn A.
Published: January 2018

In the last 15–20 years, ultrastructural studies have added new important cytological information to the relatively rich literature on the morphology and light microscopy of nectaries. On the basis of these studies, the following main conclusions can be drawn regarding the relation between the ultrastructure of nectaries and the process of nectar secretion: (1) the transport of the pre‐nectar in the nectariferous tissue is mainly via the symplast; (2) the ER alone or the ER and the Golgi apparatus are involved in the process of secretion; (3) the elimination of nectar from the protoplast of the secretory cells is by reverse pinocytosis; (4) the outer walls of the secretory cells of nectaries in many plants possess wall ingrowths.
APICAL DOMINANCE: THE EFFECTS OF GROWTH REGULATORS ON THE GAMETOPHYTE OF ANEMIA PHYLLITIDIS
Authors: Reynolds Thomas L. , Corson George E.
Published: January 2018

Gametophytes of the fern, Anemia phyllitidis (L.) Sw. were aseptically cultured until nearly mature, then collected and surgically divided into meristematic and nonmeristematic halves. Indoleacetic acid, benzyladenine, abscisic acid, and the auxin inhibitor, triiodobenzoic acid, were employed to elucidate the role of growth regulators during regeneration of adventitious gametophytes. Explants possessing actively growing meristems failed to produce adventitious thalli regardless of treatment. Untreated nonmeristematic halves initiated numerous filamentous outgrowths within two weeks of excision. These outgrowths eventually developed into the cordate prothalli typical of this species. Nontoxic levels of IAA (10−4 g/1 and 10−5 g/1) promoted early regeneration by basal explants. TIBA, at 10−5 m, completely suppressed regeneration. Benzyladenine, at 10−2 g/1, exerted its most striking effect by greatly increasing the number of adventitious outgrowths formed by treated basal explants. ABA at all concentrations delayed regeneration and reduced the number of basal halves that displayed renewed mitotic activity. This evidence suggests that auxin acts as an essential promoter of regeneration, and that the maintenance of endogenous hormonal interactions is necessary to preserve the form of an intact gametophyte.
AERENCHYMA DEVELOPMENT IN WATERLOGGED PLANTS
Authors: Kawase Makoto , Whitmoyer Robert E.
Published: January 2018

Aerenchyma development in waterlogged Helianthus annuus, Lycopersicon esculentum, and Salix fragilis was studied. More than half of the root cortical tissue sometimes became an air cavity in willow roots which developed in water. There was no cortical aerenchyma in the terminal portion, but more advanced aerenchyma developed towards the base of the sunflower roots formed in water. Waterlogged sunflower and tomato plants developed lysigenous aerenchyma in the cortex of waterlogged stems within two days.
FINE STRUCTURE OF MISTLETOE POLLEN. III. LARGE‐FLOWERED NEOTROPICAL LORANTHACEAE AND THEIR AUSTRALIAN RELATIVES
Authors: Feuer Sylvia M. , Kuijt Job
Published: January 2018

Pollen of all large‐flowered neotropical loranthaceous genera and related Australian taxa (Nuytsia, Atkinsonia) were examined in the light, scanning, and transmission electron microscopes. Trilobate, deeply concave, peroblate or oblate pollen shapes are basic within the complex; triangular, slight convex, suboblate shapes are more derived features. The non‐fixiform pollen of Atkinsonia is unique within the family. Most of the large‐flowered genera possess exclusively syncolpate aperture types. However, among Psittacanthus species tricolpate, diplosynrugate and diplorugate apertures are also present, representing derived types for the complex. The inaperturate pollen of Atkinsonia appears to have developed independently within the family. Pollen sculpturing is typically non‐uniform, i.e., there are pronounced sculpturing differences in polar and equatorial regions. Uniformly sculptured pollen is restricted to Atkinsonia, Ligaria and some species of Psittacanthus. Ultrastructurally, most exine modifications have occurred in the equatoral ektexine. Here the basic organization ranges from essentially columellaless to columellate, the latter the more derived condition. Endexine is typically thick and stratified in polar areas, thin and lamellate in peripheral and apertural regions. Similar pollen morphologies of Nuytsia and Gaiadendron support the idea of a transoceanic evolutionary connection between the Old and New Worlds. Pollen characters show Gaiadendron to be the most primitive and Psittacanthus the most advanced among the large‐flowered neotropical genera.
POLLEN MORPHOLOGY IN THE GENUS MIMULUS (SCROPHULARIACEAE) AND ITS TAXONOMIC SIGNIFICANCE
Authors: Argue Charles L.
Published: January 2018

The pollen morphology of 117 species and varieties of Mimulus was examined by light and scanning electron microscopy. Five major and 8 more tentative, minor types were found based on the differential correlation of aperture type, exine morphology, pollen grain diameter and other characters: type 1—synaperturate, usually ±spiraperturate, exine perforate to microreticulate with supratectal processes; type II—trocolporate, exine microreticulate (IIa and IIb, supratectal processes absent; IIa, mean polar axis 16–19 μm; IIb, mean polar axis 25–35 μrn; IIc, supratectal processes present); type III—tricolpate, colpus membrane ±psilate. exine with supratectal processes (IIIa, exine microreticulate and 1.4–2.0 μm thick, polar axis ≥ 30 μm; 111b, exine densely perforate and 2.2–2.8 μm thick, polar axis ≤ 23 μm); type IV—tricolpate, colpus covered with spinulose granules (operculate), exine microreticulate with supratectal processes; type V—5–7 stephanocolpate (Va and Vb, colpus margins ±straight and nongranular; Va, exine microreticulate with supratectal spinules; Vb, exine perforate with supratectal spinules or spinulose verrucae; Vc, colpus margins ragged and granular, exine microreticulate with supratectal processes). The pollen data correlate well with geographical and macromorphological data and, where the latter are ambiguous, often provide important clues toward the resolution of conflicting interpretations of infrageneric classification and generic delimitation.
DEVELOPMENTAL FEATURES OF THE SPERMATOGENOUS CELL IN GINKGO BILOBA
Authors: Gifford Ernest M. , Larson Susan
Published: January 2018

A “double‐blepharoplast” originates de novo in the spermatogenous cell of Ginkgo biloba L. Initially, the double‐blepharoplast consists of two opposing hemispherical bodies comprised of densely staining material. The two blepharoplasts seemingly are pushed apart by the formation of densely packed fibrils which are oriented perpendicular to the distal, rounded edges of the two future blepharoplasts. As the latter move apart, each one develops lightly staining channels which are often organized in a hub and spoke configuration (procentrioles). Microtubules extend from the blepharoplasts as the latter move to their final position in the cell, and centrioles (probasal bodies) become organized at the periphery of each blepharoplast. Two large “osmiophilic globules,” conspicuous entities close to the nucleus of the mature spermatogenous cell, arise de novo. A fibrillogranular body in the cytoplasm, always closely associated with the nucleus, also arises de novo.
A FOSSIL EQUISETUM SP. (FAMILY EQUISETACEAE, SUBGENUS HIPPOCHAETAE) FROM THE LATE TERTIARY ASH HOLLOW FORMATION OF NEBRASKA
Authors: Thomasson Joseph R.
Published: January 2018

Silicified leaf‐sheath fragments of Equisetum sp. are described from Late Tertiary strata in west‐central Nebraska. The close affinity of these fossils to the subgenus Hippochaetae is supported by the presence of sunken stomata arranged in two regular rows on each leaf‐sheath segment. This is the first report of the genus Equisetum from the late Tertiary Ash Hollow Formation of central North America.
OBSERVATIONS ON THE ECOLOGY AND EVOLUTION OF QUAKING ASPEN, POPULUS TREMULOIDES, IN THE COLORADO FRONT RANGE
Authors: Mitton Jeffry B. , Grant Michael C.
Published: January 2018

Three protein polymorphisms and annual width increments measured from cores were used to study the ecology and evolution of quaking aspen, Populus tremuloides Michx., in the Front Range of Colorado. Correlations among elevation, age and diameter of the largest standing ramet, and sex and mean growth rate of 106 clones are reported and discussed. The variance of growth rate was apportioned within and among ramets of a clone; the majority of the variance is environmental, with broad heritability estimated as less than or equal to .32. Analyses of gene and genotypic frequencies of polymorphic proteins revealed little differentiation with elevation, but substantial differences between the sexes. For one of three pairwise tests, the genotypes are not distributed independently of one another; linkage disequilibrium between a peroxidase locus and phosphohexose isomerase is significantly different from zero. Multiple regression revealed a positive correlation between mean growth rate and degree of heterozygosity.
THE CYTOLOGY OF POLLEN ABORTION IN S CYTOPLASMIC MALE‐STERILE CORN ANTHERS
Authors: Lee Sheu‐Ling Janet , Earle E. D. , Gracen V. E.
Published: January 2018

The anther development of the S male‐sterile cytoplasm and the fertile maintainer (N) cytoplasm versions of corn inbred W182BN and the restored S cytoplasm version of inbred NY821LERf was studied by light and electron microscopy and compared to pollen abortion in the C and T types of male‐sterile cytoplasms. The S anthers did not deviate from the non‐male sterile (N) anthers until a very late stage of pollen development. Tapetal cells developed and disappeared normally in the S version which differentiates this cytoplasm from the C and T types. Although some modified membranous structures were seen in a higher frequency in the large vacuole of the sterile S pollen than in the N and restored S counterparts, the mitochondria and other organelles in the S pollen appeared normal up to the time of pollen abortion. Pollen abortion in the S cytoplasm did not occur until the developing pollen was nearly mature. At this time the pollen grains disintegrated abruptly but other anther tissues appeared unaltered. The male sterility of S plants appeared to be determined by the pollen itself without external influence from the tapetum.
FLORAL PARAMETERS, BREEDING SYSTEM AND POLLINATOR TYPE IN TRICHOSTEMA (LABIATAE)
Authors: Spira Timothy P.
Published: January 2018

Diversity in flower size and degree of exsertion of anthers and stigma from the corolla in the California species of Trichostema appear to be correlated with breeding system and pollinator type (bee vs. bird). Autogamous (self‐pollinating) species unlike xenogamous (cross‐pollinating) species lack spatially separate anthers and stigma and nototribic pollination. The outcrossing species have significantly larger flowers, significantly larger nectar volumes and significantly higher pollen‐ovule ratios than do selfing species. Because autogamous species are less reliant on flower visitors to facilitate pollination, there may be relaxed selection for large nectar producing flowers. Pollen‐ovule ratios are correlated with breeding system and reflect the efficiency of pollen transport. Data on floral parameters suggest xenogamous species expend more energy per floral unit and are less efficient seed producers than closely related autogamous species.
THE EFFECT OF TEMPERATURE AND PHOTOPERIOD ON THE DEVELOPMENT OF GEOGRAPHICALLY ISOLATED POPULATIONS OF FUNARIA HYGROMETRICA AND WEISSIA CONTROVERSA
Authors: Dietert Margaret F.
Published: January 2018

Geographically isolated populations of Funaria hygrometrica Hedw. and Weissia controversa Hedw. were cultured under controlled axenic conditions in the laboratory to determine the developmental variability found between and within two species of widespread distribution. Funaria plants were found to grow more rapidly than those of Weissia; the latter could not be induced to complete the life cycle in culture, and generally had a less broad tolerance to environmental extremes than did Funaria. Optimum temperatures of 30 C for spore germination and 25 C for protonematal growth and gametophore formation were observed in all populations of Funaria. Gametangial formation required cooler temperatures in all populations; however, optimal temperature requirements and sporophytic growth characteristics were population‐dependent. The temperature responses of the various stages of the life cycle correlate well with seasonal temperature fluctuations that might be expected in nature. The presence of ecological races in Funaria hygrometrica is demonstrated in the behavior of the reproductive stages of the life cycle.
STORAGE PRODUCTS IN SPORES OF ONOCLEA SENSIBILIS L
Authors: DeMaggio A. E. , Stetler D. A.
Published: January 2018

Lipids and proteins in substantial quantities are present as storage products in spores of Onoclea sensibilis. They fill the sparce spore cytoplasm and ultrastructurally are indistinguishable from reserve materials observed in storage tissue of higher plants. Hydrolysis of both products is correlated with early stages in spore germination.
PEARL BODIES OF A NEOTROPICAL TREE, OCHROMA PYRAMIDALE: ECOLOGICAL IMPLICATIONS
Authors: O'Dowd Dennis J.
Published: January 2018

Multicellular, spherical or club‐shaped pearl bodies characterized by large intracellular lipid vesicles are produced on leaves and stems of juvenile Ochroma pyramidale, a tree of second growth vegetation in lowland wet forest of the neotropics. Several lines of evidence suggest that pearl bodies are linked to maintenance of foraging ants on the plant: (1) their production is closely associated with foliar nectar secretion; (2) they are abundant on saplings grown in the glasshouse (averaging 402 bodies leaf–1) but were not observed in the field where ants are predictably associated with Ochroma samplings; (3) pearl bodies are energy‐ and lipid‐rich averaging 27.80 kJ/g dry wt–1 and 74.4% lipid; (4) they are constricted at the base and easily detach from the leaf; (5) four ant species collect pearl bodies from artificial depots and return them to their nests. Chelaner sp. detaches pearl bodies from the leaf and returns them to the nest. Production of pearl bodies represents about 25% of the energy allocated to foliar nectar by saplings.

Characteristics of the pearl bodies of Ochroma are consistent with those of a widespread group of trichomes and leaf emergences suggesting a common ecological role as ant food for these structures.
CHROMOSOME NUMBERS IN THE PHASEOLEAE (FABACEAE:FABOIDEAE) AND THEIR RELATION TO TAXONOMY
Authors: Lackey James A.
Published: January 2018

Chromosome numbers are reported for 33 species of the tribe Phaseoleae. Six reports are first counts for their species; one report (Ophrestia hedysaroides) is a first count for the genus. This increases the number of genera counted to 53 out of a total 84 for the tribe. A survey of base numbers shows a general pattern of numbers 10 or 11, the same base numbers as in the neighboring tribes Dalbergieae sensu lato, Galegeae sensu lato, and Abreae. The chromosomes are generally small and polyploidy is uncommon. Deviations from base numbers 10 or 11 are mostly found in those genera with morphological pecularities and puzzling taxonomic placements: Erythrina (21), Clitoria (8, 11, 12), Butea (9), Calopogonium (18), Teramnus (14), and Strongylodon (14). Two genera have base numbers which suggest derivation by polyploidy: Glycine (20) and Cologania (22).
ELECTRON MICROSCOPE STUDIES ON THE MORPHOGENESIS OF PLASTIDS. X. ULTRASTRUCTURAL CHANGES OF CHLOROPLASTS IN MORNING GLORY LEAVES EXPOSED TO ETHYLENE
Authors: Toyama Susumu
Published: January 2018

Electron microscopic studies were made on chloroplasts of morning glory leaves exposed continuously to ethylene (6.5 ppm) for 5 days. The leaves gradually became tinged with yellow and finally were shed. The chloroplasts suffered severe injury when plants were exposed to ethylene, i.e., normal thylakoidal membranes collapsed resulting in the formation of macrograna, and then the plastids became filled with many plastoglobules. With such a metamorphosis of chloroplasts, a great deal of phytoferritin was produced in the stroma. Plastid degeneration in this manner was similar, to a certain extent, to that in morning glory leaves exposed to ozone and in leaves undergoing natural senescence. Ethylene exposure rapidly induces senescence of plant organelles, especially chloroplasts.
PHYLOGENETIC IMPLICATIONS FROM CUTICULAR WAX ANALYSES IN EPILOBIUM SECT. ZAUSCHNERIA (ONAGRACEAE)
Authors: Bowman Robert N.
Published: January 2018

Analysis of n‐alkane constitutents of the leaf cuticle have been utilized to elucidate phylogenetic relationships within Epilobium section Zauschneria. Specimens representing 136 populations were greenhouse‐grown under the same conditions. Crosses were made between representatives of all taxa within the section. The resulting F1 generations were also grown under the same conditions. Cuticle samples were removed in chloroform, purified with column chromatography and analyzed using gas chromatography and mass spectrometry. Resultant data were computer analyed using discriminant function analysis. Based on percent composition of 12 n‐alkanes, each population and taxon can be characterized by a distinctive wax profile. Results suggest that the tetraploids E. canum subsp. canum and E. canum subsp. latifolium have been derived from the anastomosis of two distinct diploid genomes, E. canum subsp. canum “angustifolium” and E. septentrionale. Biochemical evidence from extant populations of E. canum are in agreement with geographic positions and ranges of the diploid species involved. Greenhouse hybridizations between the respective diploids, E. canum subsp. canum “canum” and E. septentrionale, result in F1 progeny possessing phenotypes similar to naturally occurring tetraploid E. canum populations. Wax compositions of the natural tetraploid populations are intermediate between diploids and vary depending on geographical proximity to diploid species. Past taxonomic treatments of the genus have placed the tetraploid Zauschneria arizonica within the species Z. californica (now E. canum). Analysis of wax compositions now suggets that Z. arizonica had an independent origin which involved, at least in part, the diploid species E. canum subsp. garrettii from Utah.
INFLORESCENCE AND FLOWER DEVELOPMENT IN THE PIPERACEAE. I. PEPEROMIA
Authors: Tucker Shirley C.
Published: January 2018

Flowers of Peperomia species are the simplest structurally of any of the members of the Piperaceae. The spicate inflorescences form terminally and in axillary position; in each, the apex first is zonate in configuration with a two‐layered tunica while 3‐4 leaves are initiated. Later, when the inflorescence apical meristem begins bract initiation, the biseriate tunica persists, but zonal distinctions diminish and the apex can be described in terms of a simple tunicacorpus configuration. The inflorescence apex aborts after producing 30‐40 bracts in acropetal succession an abscission layer forms across the base of the apex, and the meristem dries and drops off. Bracts are produced by periclinal divisions in T2 (and occasionally also in the third layer as well); the later‐formed floral apices arise by periclinal divisions in T2 and the third layer. Each floral apex is at first a long transverse ridge in the axil, perpendicular to the long axis of the inflorescence. This establishes bilateral symmetry in the flower, which persists throughout subsequent growth. The floral meristem becomes saddle‐shaped, and two stamen primordia are delimited, one at either end and lower than the central floral apex. A solitary carpel is initiated abaxially, and soon forms a circular rim which heightens as a tube with an apical pore. Within the open carpel, a solitary ovule is initiated from the entire remains of the floral apical meristem; it, hence, is terminal in the flower, and its placentation is basal. Carpellary closure in P. metallica results from accelerated growth of the abaxial lip, and the two margins become appressed. Species differ greatly as to whether the abaxial or the adaxial lobe predominates in late stages of carpel development. In P. metallica, the receptive portion of the stigma forms from the shorter lobe which is overtopped. Stigmatoid tissue forms internal to the receptive stigma. The prevailing bilateral floral symmetry, absence of a perianth, and the spicate inflorescence are features which distinguish Peperomia (and Piperaceae) from the magnolialian line of angiosperms.
AN UNUSUAL BOTRYOPTERID SPORANGIAL AGGREGATION FROM THE MIDDLE PENNSYLVANIAN OF NORTH AMERICA
Authors: Millay M. A. , Taylor T. N.
Published: January 2018

A new fertile species of Botryopteris (Botryopteridaceae: Filicales) is described from four incomplete Middle Pennsylvanian specimens. Fertile pinnae of B. cratis sp. n. consist of branched frond members bearing numerous globose sporangia. Surrounding the sporangial aggregations are larger sterile frond members (0.5‐1.5 mm diam). Fertile pinnae are oval in transverse section and possess an eccentrically developed cortex composed chiefly of fibers. Some frond members show the typical botryopterid xylem configuration with three protoxylem strands. Spherical sporangia are loosely aggregated on the smallest pinnae by short, broad stalks. The annulus is band‐like, two cells high, and extends transversely across the lower half of the sporangium for approximately half the circumference. Spores are oval, trilete, verrucate, and covered by a thin separable layer. Sporangium morphology is like that of Botryopteris antiqua, but the spores closely resemble those of B. globosa. The new species is unlike previously described fructifications of Botryopteris in exhibiting a small pinna system which surrounds smaller pinnae bearing sporangia in an aggregation. The new form is considered to be less specialized than previously described globosoid forms because the sporangia are much less crowded. Isolated frond members, believed to belong to the new species, have a large central arm in the pinna xylem trace that resembles the Stephanian taxon B. renaultii. Small stems attached to the adaxial surface of frond members are radial, protostelic, centrarch, and have a three‐zoned cortex. The inner cortical zone contains large elongate cells with distinctive layered deposits. Stems are covered with uniseriate multicellular hairs on multicellular bases. Stems compare closely with B. mucilaginosa in histological features.
ARCHAEOLEERSIA NEBRASKENSIS GEN. ET SP. NOV. (GRAMINEAE‐ORYZEAE), A NEW FOSSIL GRASS FROM THE LATE TERTIARY OF NEBRASKA
Authors: Thomasson Joseph R.
Published: January 2018

Archaeoleersia nebraskensis, gen. et sp. nov. was collected from the Late Miocene Ash Hollow Formation in Garden County, Nebraska. The remains consist of anthoecia (fertile lemmas and paleas) preserved as silicifications. Examination of anthoecia by scanning electron microscopy revealed prickle hairs, simple projections, and microhairs. The fossils compare most closely with living Leersia ligularis Trin. of Central and South America. Archaeoleersia nebraskensis resembles more southern living taxa and suggests that climatic deterioration during the Late Tertiary or Quaternary resulted either in a southward migration of ancestral North American forms or in the elimination of North American populations of already widely distributed ancestral forms. Associated flora and fauna indicate a mesic, lacustrine paleoenvironment for Archaeoleersia nebraskensis.
ULTRASTRUCTURE OF SPOROGENESIS IN A MOSS, DITRICHUM PALLIDUM. III. SPORE WALL FORMATION
Authors: Brown Roy Curtiss , Lemmon Betty E.
Published: January 2018

Ultrastructural evidence indicates that marked cytoplasmic polarity occurs during wall and aperture ontogeny in spores of the moss (Musci),Ditrchum pallidum(Hedw.) Hampe. Shortly after cytokinesis, an extensive system of microtubules underlies the entire distal spore surface where exine deposition is initiated. These microtubules appear to be focused on the plastid. The apposition of slips nearly of membrane dimension contributes to the forming exine. As the lamellate exine thickens and extends to the proximal surface, the plastid and associated nucleus migrate to the proximal surface where an elaborate system of microtubules involved in aperture development is generated. The exine gradually loses its stratiform character, becoming homogenous and eventually papillate. At maturity, the spore wall consists of four layers, the outermost perine, the exine, a separating layer, and the intine. The aperture is a complex, localized modification of these layers on the proximal surface. It consists of a pore containing a fibrillar material surrounded by a thin annulus.
TAXONOMY OF ZEA (GRAMINEAE). II. SUBSPECIFIC CATEGORIES IN THE ZEA MAYS COMPLEX AND A GENERIC SYNOPSIS
Authors: Iltis Hugh H. , Doebley John F.
Published: January 2018

A compromise classification of the genus Zea, reflecting both phylogeny and practical needs, recognizes six taxa, as follows: Section Luxuriantes: Zea perennis. Zea diploperennis, Zea luxurians. Section Zea: Zea mays ssp. mexicana (Neo‐volcanic Plateau), Zea mays ssp. parviglumis Iltis & Doebley ssp. n. var. parviglumis (Rio Balsas drainage, Pacific slope from Guerrero to Jalisco), Zea mexicana ssp. parviglumis var. huehuetenangensis Iltis & Doebley var. n. (Pacific slope, western Guatemala, Prov. Huehuetenango), Zea mays ssp. mays. The new subspecies is distinguished by smaller spikelets and rachis joints, the varieties by different habitats, blooming dates and their genetic behavior in relation to cultivated Zea mays. Zea mays ssp. mexicana is the ancestor of corn.
EFFECTS OF SULFUR DIOXIDE AND OZONE ON GROWTH OF HYBRID POPLAR LEAVES
Authors: Noble Reginald D. , Jensen Keith F.
Published: January 2018

Hybrid poplar plants were exposed to 0.5 ppm SO2, 0.25 ppm O3 or 0.5 ppm SO2 + 0.25 ppm O3, 12 hr/day for 24 days to ascertain their effects on leaf growth and abscission. The data revealed that both O3 alone and O3 + SO2 promoted leaf abscission, while SO2 alone had no effect. Leaf area and dry weight were reduced while leaf abscission was stimulated by ozone fumigation. The interaction found between SO2 and O3, with all the parameters measured, was an antagonistic relationship in which SO2 reduced the toxic effect of ozone. The data analyzed, in relation to leaf position, demonstrated that ozone did not affect development of the six youngest rapidly growing leaves. However, ozone significantly reduced both leaf area and leaf weight, at later stages of development.
MITROSPERMUM VINCULUM SP. NOV., A CARDIOCARPALEAN OVULE FROM THE UPPER PENNSYLVANIAN OF OHIO
Authors: Grove Gary G. , Rothwell Gar W.
Published: January 2018

Numerous anatomically preserved ovules assignable to the genus Mitrospermum have been discovered in Upper Pennsylvanian sediments of Eastern Ohio. Although basically similar to Mitrospermum compressum, the newly discovered specimens exhibit several consistent differences. Ovules are strongly platyspermic, up to 4.2 mm long, 4.0 mm wide, and 0.6 mm thick. In the minor plane, ovules are broadest at the base and taper toward the micropyle. The integument exhibits three topographic regions: endotesta, sclerotesta, and sarcotesta. The sarcotesta is extremely broad in the major plane, where it forms two membranous wings. A single terete vascular bundle enters the base of the ovule, traverses the integument, and divides to form two integumentary bundles and a conspicuous nucellar platform. Integumentary bundles extend toward the tip of the ovule at the margin of the sarcotesta and sclerotesta. A pollen chamber with a prominent nucellar beak is delimited at the tip of the nucellus. Consistent differences in vascularization, size, nature of the seed base, features of the pollen chamber, and the Late Pennsylvanian age demonstrate that the specimens represent a distinct species. The discovery of these ovules extends the stratigraphic range of Mitrospermum to the Upper Pennsylvanian of Ohio.
ULTRASTRUCTURE OF DEVELOPING AND MATURE NONARTICULATED LATICIFERS IN THE MILKWEED ASCLEPIAS SYRIACA L. (ASCLEPIADACEAE)
Authors: Wilson Kathryn J. , Mahlberg Paul G.
Published: January 2018

The ultrastructure of developing and mature nonarticulated laticifers in Asclepias syriaca L. (the common milkweed) was studied by conventional fixation and staining techniques and by osmium impregnation techniques. The mature laticifer protoplast in A. syriaca possesses a large central vacuole with an intact vacuolar membrane. Formation of this vacuole apparently results from dilation and subsequent enlargement of endoplasmic reticulum and possibly in part by fusion of smaller vacuoles and limited cellular‐lytic autophagy. Widespread digestion or autophagy of cytoplasm within vacuoles is not evident. Nuclei, mitochondria, dictyosomes, and small vesicles are the most prominent components distributed in the peripheral cytoplasm. Plastids appear to degenerate as the laticifer matures. The specialized cellular component, latex, which is the vacuolar content of the laticifer, is interpreted to be produced in the cytoplasm and subsequently incorporated into the large central vacuole. Rubber globules, the most prominent latex component, are surrounded by a membrane that does not have a trilaminate structure. Globules are associated with an electron‐dense fibrillar component in the vacuole.
BARINOPHYTON CITRULLIFORME (BARINOPHYTALES INCERTAE SEDIS, BARINOPHYTACEAE) FROM THE UPPER DEVONIAN OF PENNSYLVANIA
Authors: Brauer David F.
Published: January 2018

Barinophyton citrulliforme is definitely proven to be a tracheophyte. The vascular cylinder of the main axis is an exarch protostele composed of tracheids having a continuous secondary wall folded into protrusions into the cell lumen. These protrusions delineate the position of annular thickenings which were deposited earlier than the continuous secondary wall. Between successive protrusions, the later‐deposited secondary wall is interrupted by minute pitlike structures. It is suggested that the secondary walls of the tracheids were laid down in a two‐phase depositional sequence. The fertile system of B. citrulliforme consists of a main axis bearing spirally arranged strobili. The strobilus consists of an axis that bears two alternate rows of sporangiferous appendages. The sporangiferous appendages are borne laterally along the strobilar axis and recurve abaxially around the axis. The sporangia are attached along the inside curve of the appendages, one sporangium per appendage, each containing both microspores and megaspores. This species thus exhibits sporangial heterospory which is considered to be an adaptation to an aquatic habit and the sporangia are considered to be functional analogs of the sporocarps of Marsilea. The interpretation of the strobilus is morphologically identical to Ananiev's interpretation of the strobilus of Pectinophyton bipectinatum; consequently P. bipectinatum is here transferred to Barinophyton as B. robustius comb. nov.
THE TERMINAL VELOCITY AND DISPERSAL OF SPINNING SAMARAS
Authors: Green Douglas S.
Published: January 2018

Strobe photographs were taken of over 200 spinning samaras from seven species of trees. These were used to measure the rate of descent, angular velocity, orientation, and other parameters of the samaras as they fell. These data were then used to compare the aerodynamic behavior of samaras, helicopters, and theoretical ideal rotors. Plotting morphological data for each samara against its rate of descent showed that this rate was highly correlated with the square root of the samara's wing loading (samara weight divided by wing‐surface area). This plot demonstrated the existence of two distinct groups of samaras, distinguished by their morphology, spinning motion, and rate of descent. These results are of greatest use in characterizing local dispersal patterns.
MORPHOLOGY AND ANATOMY OF RESIN GLANDS IN SALIX LUCIDA (SALICACEAE)
Authors: Curtis John D. , Lersten Nels R.
Published: January 2018

Resin glands on the first leaves to emerge occur at the tip of each marginal dentation of the lamina and stipule, and on the adaxial surface of the stipule and lamina bases (the latter often extend onto the petiole). Successive emerging leaves show increases in number of basilaminar glands, because increasingly elaborate multiglandular stalks develop. Glands in all locations are conical or domed, with a palisade‐like epidermis subtended by 5–6 layers of parenchyma which contains druse crystals. A single vascular bundle (sometimes two or three) ends in a small knob of tracheary elements. Glands usually secrete liquid resin that covers the gland and surrounding area and under certain conditions, particularly in low humidity, resin is extruded as a filament from a pore in the gland apex, a mode of resin secretion not described previously. Glands secreting liquid resin have an apical dimple, but presence of a pore has not been established.
REPRODUCTIVE DEVELOPMENT IN LOBLOLLY PINE: I. THE EARLY DEVELOPMENT OF MALE AND FEMALE STROBILI IN RELATION TO THE LONG SHOOT GROWTH BEHAVIOR
Authors: Greenwood Michael S.
Published: January 2018

The timing and patterns of initiation and differentiation of strobili on three clones of loblolly pine located in Washington, N.C., were similar, although the cone‐producing abilities of these clones were significantly different over a 5‐yr period. Male strobili were initiated in early July and were differentiated by mid‐September. Female strobili were initiated about the last week in August and were fully differentiated by mid‐November. There were significant differences in the developmental patterns of the long shoots on these three clones.
ALLELOPATHIC INHIBITION OF NITRIFICATION AND NITRIFYING BACTERIA IN A PONDEROSA PINE (PINUS PONDEROSA DOUGL.) COMMUNITY
Authors: Lodhi M. A. K. , Killingbeck Keith T.
Published: January 2018

The dynamics of ponderosa pine (Pinus ponderosa Dougl.) stands in western North Dakota were studied to determine the influence of plant‐produced chemicals on nitrification rates and competitive interactions within the stands. Ponderosa pine accounted for more than 98% of all tree and shrub stratum stems in this climax community. Low levels of nitrate‐nitrogen relative to ammonium‐nitrogen and low numbers of Nitrosomonas and Nitrobacter in the soils indicated that nitrification rates were low. Inhibition of nitrification is often attributed to low soil pH in coniferous forests, but the slightly alkaline soils in this study (pH 7.25–7.75) suggested that another factor caused the low nitrification. Evidence obtained suggested that the reduction in nitrate synthesis was due to the production and subsequent transfer to the soil of secondary plant chemicals that were toxic to Nitrosomonas. Chemical inhibitors of nitrification, including caffeic acid, chlorogenic acid, quercitin, and condensed tannins, were found in extracts from ponderosa pine needles, bark, and A horizon soils. These extracts proved to be toxic to soil suspensions of Nitrosomonas causing reductions of from 68–93% of the control. These findings indicate that climax ponderosa pine communities minimize the conversion of ammonia‐nitrogen to nitrate‐nitrogen by chemically inhibiting nitrification.
THE POSSIBLE ROLE OF A FIBROUS BODY IN THE GENERATIVE CELL OF THE POLLEN GRAIN OF TILLANDSIA CAPUT‐MEDUSAE MORR. (BROMELIACEAE)
Authors: Brighigna Luigi , Fiordi Ambretta Cecchi , Palandri Maria R.
Published: January 2018

The occurrence of a fibrous body in the generative cell of the pollen grain of Tillandsia caputmedusae Morr. (Bromeliaceae) is pointed out and its possible role is indicated.
METABOLIC PRIORITIES WITH RESPECT TO GROWTH AND MINERAL UPTAKE IN ROOTS OF HORDEUM, TRITICUM AND LYCOPERSICON
Authors: Crapo N. L. , Ketellapper H. J.
Published: January 2018

Reduction in the supply of photosynthate to the roots of tomato, barley, and wheat plants was achieved indirectly by lowering the intensity of sunlight striking the foliage of test plants. The decrease in sugar and starch concentrations in the roots was verified by appropriate extraction and colorimetric analysis, and a corresponding reduction in the total respiratory rate of the roots was confirmed using an oxygen tension monitor. Other processes measured directly include the rate of uptake of potassium, the mitotic quotient in the root tip—a measure of growth—and the rate of accumulation of dry matter in the root. The study demonstrated that of the metabolic activities observed, root growth is the process first limited when the supply of photosynthetic fuel is decreased. Root growth was severely inhibited under conditions that did not significantly affect either the active uptake of potassium per gram of root or total respiration per gram of root. With greater restriction of photosynthesis, growth was completely halted while the uptake of potassium was strongly decreased and total respiration was still affected only moderately. As the light intensity is reduced significantly, most of the reduced energy supply in the root appears to be used in support of processes critical to maintenance of the organ and the organism.
A MORPHOMETRY STUDY OF THE ULTRASTRUCTURE OF ECHINOCEREUS ENGELMANNII (CACTACEAE). II. THE MATURE, ZONATE SHOOT APICAL MERISTEM
Authors: Mauseth James D.
Published: January 2018

The shoot apical meristems of adult Echinocereus engelmannii plants are zonate and have a tunica, central mother cells, a peripheral zone, and a pith‐rib meristem. An ultrastructural, stereological study showed that each zone has its own distinct ultrastructure, but that the differences between the zones are quite small, both on a protoplasmic basis and on a cytoplasmic basis. Furthermore, the ultrastructure present in the adult apices differed only slightly from that which had been found in seedling apices, demonstrating a long‐term stability of structure. The standard deviations found in the sample were small, indicating little variability from one plant to the next and suggesting that there are little or no cyclic changes during the plastochron or a 24‐hr photoperiod. The ultrastructures found in the shoot apical meristems differed significantly and markedly from mature tissues of the same plants.
ULTRASTRUCTURAL AND PALEOBIOCHEMICAL CORRELATIONS AMONG FOSSIL LEAF TISSUES FROM THE ST. MARIES RIVER (CLARKIA) AREA, NORTHERN IDAHO, USA
Authors: Niklas Karl J. , Brown R. Malcolm
Published: January 2018

Miocene angiosperm leaf tissues of Betula, Hydrangea, Platanus, and Quercus, and of Castanea, Persea, and gymnospermous tissues from offshore and onshore lacustrine sediments, respectively, reveal various states of ultrastructural detail in preservation which correlate with their paleobiochemical profiles. Excellent cytologic preservation of membrane‐bound organelles in offshore tissue samples is correlated with relatively mild chlorophyll and fatty acid degradation (chlorins, unsaturated hydrocarbons), while progressive deterioration of ultrastructure seen in onshore specimens is concomitant with extensive chlorophyll degradation and saturation of hydrocarbons. Comparative studies between fossils found in pyroclastic (Succor Creek Flora, Miocene) and lacustrine (Clarkia Flora) environments indicate that the degree of pre‐ and post‐depositional hydration of tissues is a less significant factor in determining preservation than redox potential and secondary metabolites (tannic acids, chlorophyll derivatives). A sequence of organelle degradation in leaf tissues is given, and it is suggested that chloroplasts and cell walls are the most stable cellular constituents, while the endoplasmic reticulum, nuclei, and mitochondria are the most labile.
THE RELATIONSHIPS BETWEEN MALE AND FEMALE FERTILITY AND AMONG TAXA IN DIPLOID WHEATS
Authors: Sharma Hari C. , Waines J. Giles
Published: January 2018

Pollen stainability appears to be a reliable indication of the ultimate seed set in diploid interspecific hybrid and backcross populations in Triticum L. The correlation between percent pollen stained and number of seeds set is positive and highly significant (r = 0.92). Estimates of male and female fertility in the hybrids and backcrosses are interpreted to indicate that the domesticated diploid Triticum monococcum L. and wild diploid T. boeoticum Boiss. em. Schiem, are one and the same species, and that T. urartu Tum. is not a variety of monococcum or boeoticum, but rather a separate species. The F1 hybrids and backcrosses between monococcum and boeoticum are normally male and female fertile. The F1 hybrids between monococcum and urartu are completely sterile and complete to partial sterility exists in backcrosses.
MORPHOLOGICAL OBSERVATIONS ON THE EARLY IMBIBITION OF WATER BY SIDA SPINOSA (MALVACEAE) SEED
Authors: Egley G. H. , Paul R. N.
Published: January 2018

The chalazal area is confirmed as the site of initial water entry into prickly sida (Sida spinosa L.) seeds. Very early during imbibition of water, a kidney‐shaped area of the seed coat separates from underlying cells forming a blister. This blister may also be induced in dry seeds (both afterripened and nonafterripened) when pressure is applied to the chalazal area. Blisters form more readily on afterripened seeds than on nonafterripened seeds, however, and the event is correlated with an increase in seed coat permeability to water. Immediately beneath the palisade layer of the blister lies a single layer of subpalisade cells. This layer is observed only in the region of blister formation. As the blister separates, the end walls of the subpalisade cells remain attached to the floor of the palisade layer. The subpalisade cells are thereby broken open, and their contents disgorged into the blister lumen. Evidence indicates that this separation of the palisade and subpalisade layers in the chalazal area initiates imbibition of water by prickly sida seeds.
FATTY ACIDS OF CUPHEA (LYTHRACEAE) SEED LIPIDS AND THEIR SYSTEMATIC SIGNIFICANCE
Authors: Graham Shirley A. , Hirsinger Frank , Röbbelen Gerhard
Published: January 2018

Fatty acid analyses of seed lipids in 46 species of Cuphea are presented, representing the first major survey of a molecular nature for the family. A remarkable diversity in composition is found, with seeds containing high amounts of several medium chain fatty acids. Lauric acid (12:0) predominates in 43% of the species studied, constituting 50–74% of the total fatty acid content. Capric acid (10:0) is the dominant fatty acid in 32% of the species, comprising as much as 87% of the total acid content. Caprylic acid (8:0) predominates in one section of the genus. The emphasis on production of fatty acids with carbon chain lengths of 12, ten, and eight carbon atoms is unique among plant genera studied to date. Among seven of the nine sections studied, one pattern of fatty acid composition predominates. Two sections have no characteristic pattern, supporting other evidence of their polyphyletic origin. The most significant systematic contribution is made by comparison of the predominate fatty acid components in the seed lipids. When used in conjunction with floral morphology, pollen studies, and chromosome number, it provides an important new basis on which to draw inferences of evolution and clarify present relationships within the genus. Additionally, a trend from the longer‐chained, unsaturated linoleic acid (18:2) as a major lipid component to shorter‐chained saturated capric and caprylic acids is correlated with increasing floral specialization. It is suggested that mutations in regulatory genes have occurred which cause fatty acid production in seeds to cease at progressively earlier stages, resulting in accumulation of large amounts of single fatty acids of progressively shorter carbon chain lengths.