bluuebunny/crossref_metadata_2025 huggingface dataset:
COMPARATIVE FECUNDITY AND POPULATION COMPOSITION OF HETEROSTYLOUS AND NON‐HETEROSTYLOUS SPECIES OF VILLARSIA (MENYANTHACEAE) IN WESTERN AUSTRALIA
Authors: Ornduff Robert
Published: January 2018

Several species of Villarsia in Western Australia are distylous, but their floral morphology is variable and mostly differs from the expected positional relationships of stigmas and anthers. Villarsia albiflora is non‐heterostylous but self‐incompatible. In the distylous V. calthifolia, V. capitata, and V. lasiosperma, morph ratios were 1:1, but in some populations of V. parnassiifolia the short morph was present in excess. Ovule production per flower of the two morphs of the distylous species varied between populations, but within most populations was equal. In nine populations of the distylous species, percentage seed‐set of Longs and Shorts was equal. In the five populations of the distylous species in which percentage seed‐set differed between the morphs, seed‐set of Longs exceeded that of Shorts. In four populations of V. parnassiifolia with Shorts in excess, percentage seed‐set of the two morphs was equal; in a fifth, that of Longs exceeded that of Shorts. Percent seed‐set of V. albiflora did not differ from that of the distylous species and remained constant during the flowering season despite a substantial decrease in ovule production during this period. This study demonstrated no reproductive advantage of distyly over monomorphism in the species studied.
FATE MAP OF THE ORGANIZING SHOOT APEX IN GOSSYPIUM
Authors: Christianson M. L.
Published: January 2018

Chimeral seedlings from a “semigametic” strain of cotton were used as the basis for a clonal analysis of events in the progressive organization of the nascent shoot apex. At the time the proembryo becomes a globular stage embryo with a distinct dermatogen, the surface of the embryo contains an eight‐celled compartment for each cotyledon, a two‐celled compartment for the first leaf, a one‐celled compartment for the second leaf, and a three‐celled compartment for the apical initials and all subsequent leaves and aerial structures. The developmental history of the first two leaves differs in a fundamental way from that of all the other leaves.
LEAF TRICHOMES OF SOME PARTHENIUM SPECIES
Authors: Healey Patrick L. , Mehta Indira J. , Westerling Karin E.
Published: January 2018

Guayule (Parthenium argentatum), a native shrub of the Chihuahuan desert, contains rubber. Guayule has been crossed with other Parthenium species in an attempt to improve its agronomic characteristics. The resulting hybrids show intermediate morphologies. Each Parthenium species has a characteristic combination of leaf trichomes. In order to recognize the contribution of each parent in future studies of hybrids, characteristics of leaf trichomes of the following Parthenium species were studied: P. tomentosum, P. fruticosum, P. Schottii and P. rollinsianum. All species studied had two or more types of trichomes, and, in some species, trichomes of upper and lower epidermal surfaces were different. The prominent trichomes on upper epidermis of P. tomentosum and P. fruticosum were simple, uniseriate, conical trichomes, which also were observed on both epidermal surfaces of P. Schottii. Extremely long, narrow, simple, whiplike, trichomes formed a dense cover on both surfaces of P. rollinsianum and on the lower surfaces of P. tomentosum and P. fruticosum. Simple, uniseriate, cylindrical trichomes, and biseriate, glandular trichomes were observed in all four species.
LEAF OPTICAL PROPERTIES OF RAINFOREST SUN AND EXTREME SHADE PLANTS
Authors: Lee David W. , Graham Rita
Published: January 2018

The optical properties of the leaves of twelve tropical sun species and thirteen tropical extreme shade species were examined with an integrating sphere attached to a spectroradiometer. Measurements of diffuse reflectance and transmittance allowed calculations of absorptance, 350–1,100 nm. Although some shade species absorbed higher percentages of quantum flux densities for photosynthesis (400–700 nm, PPFD) than the mean for the sun species, the sun and shade species as groups were not significantly different from each other: 90.2, S.D. 3.6% for shade species and 88.6, S.D. 2.4% for the sun species. The groups of species did not differ in total absorptance of energy 350–1,100 nm. Furthermore, the sun and shade species were identical in their shift of absorptance at wavelengths between 650 and 750 nm. The anthocyanic coloration of the leaf undersurfaces of two species polymorphic for this characteristic (Trionela hirsuta and Ischnosciphon pruinosus) is correlated with increased absorptance at the upper end of the action spectrum of photosynthesis. Although sun and shade species have similar optical properties, the energy investment (as documented by dry wt per unit area of leaf surface) is much less for the shade species.
PERMINERALIZED PINACEOUS LEAVES FROM THE UPPER CRETACEOUS OF HOKKAIDO
Authors: Stockey Ruth A. , Ueda Yayoi
Published: January 2018

Three fragments of fascicles of a possible five‐needle pine are described from the Upper Cretaceous Yezo Group (Santonian/Senonian) of Hokkaido. Specimens from the Omakizawa, Oyubari, Yubari City, the Koyanozawa, Ikushumbetsu, Mikasa City, and the Sankebetsugawa, Haboro are preserved in calcium carbonate nodules containing abundant ammonites. Leaves borne in apparent fascicles of five measure 0.7–0.8 mm in radial and 0.8–1.0 mm in tangential diam and are represented by short fragments of isolated needles. Thick‐walled epidermal cells on these amphistomatic leaves resemble the underlying uniform hypodermis. Two external resin canals are situated near the lateral corners toward the adaxial surface. Only slightly plicate mesophyll cells in a layer one to two cells thick border on an elliptical endodermis with thickened outer cell walls. Two to three layers of transfusion tissue surround the double vascular strand. Two vascular bundles are separated by one cell layer of sclerenchyma fibers. Small patches of abaxial and adaxial sclerenchyma fibers have also been observed. Leaves most closely resemble those of Pinus leiophylla Schl. et Cham. Subgenus Pinus, Section Pinea, Subsection Leiophyllae and P. montezumae Lamb. Subgenus Pinus, Section Pinus, Subsection Ponderosae and are described as a new species P. hokkaidoensis sp. nov. Stockey and Ueda. Close anatomical comparisons are made with this leaf and previously described permineralized Upper Cretaceous pine needles from Hokkaido and eastern North America.
XYLEM STRUCTURE IN BOTRYCHIUM DISSECTUM SPRENGEL AND ITS RELEVANCE TO THE TAXONOMIC POSITION OF THE OPHIOGLOSSACEAE
Authors: Chau Robert I.
Published: January 2018

The radially seriate xylem of Botrychium dissectum Sprengel resembles secondary xylem, particularly that of gymnosperms, in many important details. It is derived from a layer of cells which strongly resembles a vascular cambium. Presumptive cambial initials are fusiform, and derivatives are radially seriate. The walls of the initials and derivatives have a beaded appearance when viewed in tangential section. The number of xylem elements increases in seasonal increments. Circular‐bordered pit pairs occur where tracheids abut other tracheids, and specialized cross‐field pit pairs occur where they abut the radially‐aligned parenchyma or rays.

Cambial activity in Botrychium differs from that found in seed plants and progymnosperms in not producing secondary phloem. Tracheids are less similar to those known in progymnosperms than previously assumed, and some supposed similarities may be less significant than previously assumed. The significance of these dissimilarities is unclear. The recognition that the bulk of the xylem is secondary and that protoxylem strands are arranged as sympodia suggests that Botrychium may be eustelic rather than siphonostelic.
EARLY INFLORESCENCE AND FLORAL DEVELOPMENT IN ZEA DIPLOPERENNIS, DIPLOPERENNIAL TEOSINTE
Authors: Sundberg Marshall D. , Orr Alan R.
Published: January 2018

This study uses SEM and LM to investigate the ontogeny and histogenesis of the tassel and ear spikes, spikelets and florets of diploperennial teosinte, Zea diploperennis litis, Doebley, and Guzman. The pattern of development observed in this teosinte is compared to the literature descriptions of corresponding development in Zea mays L. The data indicate two distinct developmental patterns in teosinte: one characteristic of the male and mixed inflorescences; the other the female inflorescence. The branching pattern we observed in male and mixed inflorescences of diploperennial teosinte is identical to that described in both the male and female inflorescences of Z. mays. The initial primordium, a bract produced along the primary axis, subtends an axillary branch which bifurcates unequally, forming two spikelets, pedicellate and sessile. The sessile spikelet is interpreted as a branch of the pedicellate spikelet. The first bract produced on each spikelet is the outer glume. The developmental pattern of a mixed inflorescence shows a transition from distichous four‐rowed staminate spikelets to distichous two‐rowed cupulate fruitcases. At the transition node, a staminate pedicellate spikelet and a pistillate sessile spikelet is observed. In the pistillate spikelet, the outer glume becomes part of the cupulate fruitcase. In the female inflorescence, only a single spikelet forms in the axil of the initial primordium: the axillary branch primordium becomes the spikelet apex; and the initial primordium becomes the outer glume, eventually a part of the cupulate fruitcase. The first bract produced by the spikelet apical meristem is the inner glume. There is only one observable spikelet and no recognizable rudimentary spikelet, pedicellate or sessile. Therefore, while the cupulate fruitcases of female and mixed inflorescences appear identical at maturity, they do not have the same ontogeny. The evidence supports a hypothesis that the progenitor of a Z. mays ear may be a mixed teosinte inflorescence rather than a pure male tassel or pure female spike. The developmental morphology of male and female inflorescences of other Zea species should be examined.
ACID‐INDUCED FILAMENT ELONGATION IN IPOMOEA NIL (CONVOLVULACEAE)
Authors: Koning Ross E.
Published: January 2018

It has been known for some time that morning glory filaments elongate in response to increases in concentration of gibberellins (Murakami, 1973) and decreases in ethylene production (Koning and Raab, in press), but many other aspects of their growth have remained unstudied. In the present work, the possible role of gibberellin‐stimulated proton efflux in filament growth was examined. Although applied gibberellins stimulated extensive filament growth in vitro and the pH of the incubating medium became acidified during growth, gibberellin also induced growth in media buffered at alkaline pH values. Acidic buffers alone elicited only a very small amount of growth. Fusicoccin, a potent stimulator of proton efflux, initially stimulated the rate of filament growth but elicited only a small increment of growth. In fact, continued presence of fusicoccin poisoned sustained gibberellin‐induced growth. Vanadate ions, believed to inhibit proton efflux, had little effect upon gibberellin‐induced growth except at extremely high concentrations. Based upon these results, it appears that the acid‐induced component of growth stimulation by gibberellin is relatively minor in Ipomoea filaments. These results are quite different from those reported for filament elongation in Gaillardia (Koning, 1983a).
PHOTOSYNTHESIS IN THE FEMALE GAMETOPHYTE OF GINKGO BILOBA
Authors: Friedman William E. , Goliber Thomas E.
Published: January 2018

The female gametophyte of Ginkgo biloba is the only seed plant gametophyte known to contain chlorophyll. Measurements of photosynthetically active radiation (PAR) indicate that a gametophyte growing within an ovule can receive significant quantities of light (70 μmol photons m–2 s–1). Under the conditions of our experiments, whole gametophytes dissected free from ovules were capable of gross photosynthesis, but not net photosynthesis. On a dry wt basis, the maximum rate of carbon fixation under near saturating light intensities was 3.64 × 10–3 μmol CO2g–1 s–1. The unique ability of the female gametophyte of Ginkgo biloba to produce chlorophyll and engage in photosynthesis appears to result from its exposure to sufficient levels of light and a predisposition to react to this stimulus by the development of a functional photosynthetic apparatus.
FIELD GERMINATION AND SEEDLING GROWTH OF CH AND CL PROGENY OF IMPATIENS CAPENSIS (BALSAMINACEAE)
Authors: Antlfinger Ann E.
Published: January 2018

The germination behavior and early growth of chasmogamous (CH) and cleistogamous (CL) progeny of Impatiens capensis were investigated in two eastern Nebraska stands. Field germination of families of buried seeds was scored in mid‐April. In one stand a significantly higher proportion of CL seeds germinated than CH seeds while no significant differences were observed in the second stand. Among‐family variation in germination rates was significant in both stands. The time course of field germination was similar for CL and CH seeds. A sample of the germinated CL and CH seedlings, matched in size, was planted individually in pots and grown in the greenhouse for five wk. Early growth of CL and CH seedlings was similar. In addition, CL seedlings were as variable as CH seedlings for four morphological traits. Overall, a large fitness advantage for CH progeny was not detected in the germination and early growth of Impatiens capensis seedlings.
VARIATIONS IN MICROSPORANGIA AND MICROSPORE DISPERSAL IN SELAGINELLA
Authors: Koller Alan L. , Scheckler Stephen E.
Published: January 2018

Fifty‐three species of Selaginella were examined for variations in microsporangium anatomy and microspore dispersal strategies. Five anatomically different kinds of microsporangia were observed, displaying three different strategies for microspore dispersal. Xeric species, including all isophyllous species, have microsporangia that only dry and shrink as they dehisce, resulting in microspores being passively dispersed. Among anisophyllous species from tropical and subtropical habitats some species actively eject their microspores, while others of the series Articulatae eject the entire microsporangium. These two types of active ejection both utilize a mechanism similar to that found in fern leptosporangia.
POLLEN MORPHOLOGY AND SYSTEMATIC RELATIONSHIPS AMONG NEW WORLD SPECIES IN TRIBE ANTIRRHINEAE (SCROPHULARIACEAE)
Authors: Elisens Wayne J.
Published: January 2018

The morphology of mature pollen grains among 12 New World genera in tribe Antirrhineae has been examined with light and scanning electron microscopy. Pollen from 29 American species have mean polar diam that range from 17 to 26 μm, have a tectate structure with perforate, microreticulate, or reticulate surface pattern, and are subspheroidal to prolate, and trizonocolporate with fusiform or narrowly oblong colpi that are free or occasionally fused at the poles. Among the genera, pollen size is positively associated with style length but not haploid chromosome number. Three major morphological categories are recognized based on grain shape, exine structural pattern, and colpus shape. Two of these morphotypes each characterize individual genera (Mohavea, Linaria). The other morphological category includes ten New World genera and has been divided into three subcategories based on variation in lumina diam and intermittent occurrence of fused colpi. Only Antirrhinum and Pseudorontium have species or populations with pollen in more than one subcategory. Concordance of morphological, anatomical, chromosomal, and palynological data suggests that Linaria and Mohavea are best placed in separate subtribes from other native American genera. Compared to Old World taxa in tribe Antirrhineae, the most common pollen type (subspheroidal, microreticulate, apocolpate, fusiform colpi) may be the most primitive. Pollen grains with fused colpi (Antirrhinum p.p., Pseudorontium) and perforate (Mohavea) or reticulate (Holmgrenanthe) structural patterns probably represent derived types.
OBSERVATIONS ON “VAMPYRELLA PENULA‐STYLODINIUM SPHAERA” AND THE ULTRASTRUCTURE OF THE REPRODUCTIVE CYST
Authors: Timpano Peter , Pfiester Lois A.
Published: January 2018

“Vampyrella‐Stylodinium,” an artificial name for a predaceous organism of uncertain taxonomic position, has at least three distinct phases in its life history: the amoeboid phase, both free‐floating and attached; the feeding cyst or immobile phase; and flagellated gymnodinoid swarmers. The orange free‐floating amoeba has unbranched, filose pseudopodia and several contractile vacuoles. When feeding on the filamentous green alga Oedogonium, the pseudopodia shorten and rearrange. After dissolution of part of the Oedogonium cell wall, the amoeba ingests the host protoplast. Then a stalked reproductive cyst may form. This cyst changes color from green to light orange as it matures. At the time of excystment, the cyst has a smooth outer wall, a spinose inner wall, and a well‐delineated phagocytic vacuole. As this vacuole moves from its central position to the cyst's periphery, the walls rupture and 2‐4 amoebulae emerge. With TEM observations, the reproductive cyst is shown to be multinucleate. Each nucleus is eukaryotic in organization and possesses one nucleolus. Mitochondria have tubular cristae and no structures unique to the division Pyrrhophyta are observed. Although this stage of the life history does not have a dinokaryotic nucleus, the gymnodinoid swarmers that can emerge from the reproductive cyst, do. Like other parasites which have been assigned to the division Pyrrhophyta, “Vampyrella‐Stylodinium” does not conform well to the generalized concept of a dinoflagellate.
GLANDULAR HAIRS IN THE ARBUTUS XALAPENSIS COMPLEX IN RELATION TO HERBIVORY
Authors: Becerra Judith , Ezcurra Exequiel
Published: January 2018

The morphological boundaries between Arbutus xalapensis and A. glandulosa are diffuse. Many individuals share traits of both species. The character most commonly used to distinguish the species is the presence of glandular hairs in A. glandulosa. Comparisons in the field of the number of colonies and level of defoliation by Eucheira socialis (Lepidoptera, Pieridae), an Arbutus‐specific herbivore, showed that the damage is greater for glabrous than pilose trees and greater for pilose than glandular trees. Additionally, the geographic distribution of glandular trees is strongly correlated with that of E. socialis while that of non‐glandular trees is not. We suggest that the glandular and non‐glandular forms could belong to one single polymorphic species in which the glandular characteristic is maintained by differential herbivory.
PROANTHOCYANIDINS IN NEEDLES FROM SIX GENERA OF THE TAXODIACEAE
Authors: Stafford Helen A. , Lester Hope H.
Published: January 2018

Proanthocyanidin contents of needles ranged from a mean of 150 to 300 μg per mg dry wt in five species from five genera of the Taxodiaceae, Sequoiadendron giganteum (Lindl.) Bucch., Metasequoiaglyptostroboides H. Hu and Cheng, Sequoia sempervirens (D. Don) Endl., Taxodium distichum L. Rich., and Sciadopitys verticillata Siebold and Zucc. However, significantly lower amounts (70 μg per mg dry wt) were found in Cryptomeria japonica (L.f.) D. Don. This latter species as well as Sciadopitys verticillata, contained little or no prodelphinidin, while the other four species contained a ratio of procyanidin to prodelphinidin up to about 1:5. These data were based on analyses from three trees from each species. In addition, one tree from each species was examined in more detail. The major flavan‐3‐ol in all cases was (+)‐catechin, with only non‐detectable or trace amounts of (–)‐epicatechin. The triphenolic flavan‐3‐ol, (+)‐gallocatechin, was a minor constituent in all species, except Sciadopitys and Cryptomeria. The (–)‐epigallocatechin was detected in Metasequoia, Sequoiadendron and Sequoia. All contained either (–)‐epicatechin‐(+)‐catechin or (+)‐catechin‐(+)‐catechin as the major procyanidin dimer. Prodelphinidin dimers were only tentatively identified.
FEMALE FREQUENCIES IN GYNODIOECIOUS POPULATIONS CORRELATED WITH SELFING RATES IN HERMAPHRODITES
Authors: Sun M. , Ganders Fred R.
Published: January 2018

Gynodioecious populations consist of separate hermaphroditic and female individuals. Females are at a selective disadvantage because they contribute genes to the next generation only through ovules, while hermaphrodites contribute genes through ovules and pollen. For females to be maintained in populations they must have some compensating selective advantage. The outcrossing hypothesis postulates that females are maintained because their progeny result from obligate outcrossing, whereas some of the progeny of hermaphrodites result from self‐fertilization and are less fit because of inbreeding depression. If correct, the frequency of females should be positively correlated with selfing rates of hermaphrodites in populations. We found a strong positive correlation between female frequency and selfing rates of hermaphrodites (r = 0.91, P < 0.01) in eight gynodioecious populations of Hawaiian species of Bidens. Our results confirm that the obligate outcrossing of females is a major factor maintaining females in gynodioecious populations. However, the observed selfing rates are insufficient by themselves to account for the frequency of females in these populations.
CYTOLOGY OF SOME WESTERN CANADIAN ALLIUM SPECIES
Authors: Chinnappa C. C. , Basappa G. P.
Published: January 2018

Cytology of four species of Allium from western Canada was studied. Three species viz: A. acuminatum 2n = 14, A. cernuum 2n = 14, and A. schoenoprasum 2n = 16 were found to be diploids with normal meiosis. Some populations of A. cernuum and A. schoenoprasum contained a high number of B‐chromosomes. Diploid (2n = 14) and tetraploid (2n = 28) populations were encountered in A. textile. While the diploid meiosis was regular, the tetraploids showed 1–5 quadrivalents at metaphase I, suggesting their possible autoploid origin.
OCCURRENCE AND PHYLOGENETIC SIGNIFICANCE OF “SPECIAL WALLS” AT MEIOSPOROGENESIS IN COLEOCHAETE
Authors: Graham Linda E. , Taylor Claude
Published: January 2018

Within germinating zygotes ofColeochaete pulvinata,meiospores are individually surrounded by chamber walls which are ultrastructurally and chemically different from vegetative cell walls of the same species. Meiospore chamber walls exhibit the staining reactions typical of callose. They thus resemble the “special walls” present during sporogenesis in embryophytes. Their presence suggests that the charophycean green algal ancestors of land plants may have possessed spore development preadaptations influential in the evolution of walled spores, an important plant adaptation to terrestrial life.
QUANTITATIVE PATTERNS OF LEAF EXPANSION: COMPARISON OF NORMAL AND MALFORMED LEAF GROWTH IN VITIS VINIFERA CV. RUBY RED
Authors: Wolf Sue D. , Silk Wendy Kuhn , Plant Richard E.
Published: January 2018

Developmental patterns produced during normal expansion of the leaf of Vitis vinifera cv. Ruby Red are quantitatively characterized from the distribution of relative growth rates and growth velocity vectors and are compared to patterns produced during the development of an abnormally shaped leaf. The bilateral symmetry of the V. vinifera leaf, which is present in the normal leafand absent in the malformed leaf, is shown during growth by the patterns of velocity isolines. Ellipses formed by the isolines around the midrib during normal development are distorted during development of the malformed leaf. During normal growth, tissue elements are displaced in rather straight lines, resulting in streamlines which radiate outward from the petiole. Element motion in the abnormally developing leaf causes curving of streamlines. Relative growth in area of elements located in an area in the normal leaf are higher than those in the malformed leaf. The most frequently observed category of relative area growth in the normal leaf is 40%‐59% d~1, while 20%–39% d−‐1 predominates in the abnormal leaf. A spatial gradient in growth appears during normal development with lowest relative growth (20%–39% d−‐1) present in the tip region, intermediate values (40%–59% d−‐1) in the midsection, and maximum growth (> 60% d−‐1) appearing in the basal region. During development of the abnormally shaped leaf, the gradient along the midrib is disrupted with low magnitudes of growth (<20% d−‐1) appearing in the midsection of the leaf where intermediate values are expected. The theoretical and numerical distinctions between two common expressions for relative growth (relative elemental growth and exponential growth rate) are discussed. Relative elemental growth is shown to become increasingly larger than the exponential growth rate as the magnitude of growth increases relative to initial size of the tissue element. Numerical methods for evaluating relative growth based on finite element areas are compared to methods based on displacement and velocity gradients and are shown to produce similar results.
POLLEN TUBE DISTRIBUTIONS IN NICOTIANA GLAUCA: EVIDENCE FOR DENSITY DEPENDENT GROWTH
Authors: Cruzan Mitchell B.
Published: January 2018

I hand sectioned styles of Nicotiana glauca at intervals along their length and counted the number of pollen tubes in each section using fluorescence microscopy. Evidence of density dependent growth was found for three stages of pollen growth. Pollen germination on the stigma increased with increasing pollen population size. Pollen tube penetration in the stigma was unaffected by increasing density from low to moderate levels but was reduced at high densities. Pollen tube penetration in the style was enhanced by increasing density. This enhanced growth in the style was apparently confounded by interference among pollen tubes growing at high densities. In particular, the area of tissue able to support pollen tube growth decreases from the stigma into the lower style, which could cause overcrowding of pollen tubes growing at high densities. Enhanced pollen tube penetration with increasing density combined with interference among pollen tubes growing at high densities resulted in greater mean pollen tube lengths for populations with moderate densities. The shift from density independent growth in the stigma to positively density dependent growth in the style may represent a shift from autotrophic to heterotrophic growth stages of pollen.
DINITROGEN FIXATION BY CYANOBACTERIA AND ASSOCIATIVE RHIZOSPHERE BACTERIA IN THE ARAPAHO PRAIRIE IN THE SAND HILLS OF NEBRASKA
Authors: Kapustka Lawrence A. , DuBois John D.
Published: January 2018

Free‐living and lichenized cyanobacterial (cyanolichen) colonies occupy 12–29% of the surface area in the Sand Hills grasslands on the Arapaho Prairie in southwestern Nebraska. During brief periods of favorable conditions (i.e., moderate temperature and high moisture), these diazotrophs are capable of high rates of dinitrogen fixation. Maximum rates of acetylene reduction measured during 1981 and 1982 were 2,237 μg N m‐2 hr‐l. The duration of dinitrogen fixation activity is dependent upon moisture conditions; rates of acetylene reduction were shown to decline 90% in as little as three hr. Desiccated colonies resumed acetylene reduction activity within one hr and achieved equilibrium rates within four hr following rehydration.

Associative, heterotrophic diazotrophs were isolated from the rhizospheres of several grass species. These bacteria exhibited a range of culturing characteristics which may reflect differing plant‐bacterial interaction potentials important to the establishment and maintenance of the plant species. None of the field assays for heterotrophic dinitrogen fixation performed over the two‐yr period indicated a capacity of this group to provide ecologically significant levels of N in this grassland.

Our gross estimate of the annual contribution was 3.5 kg N ha‐1 from cyanolichens and 0.8 kg N ha‐1 from associative heterotrophs.
DIFFERENTIAL GERMINATION OF RAY AND DISC ACHENES IN HEMIZONIA INCRESCENS (ASTERACEAE)
Authors: Tanowitz Barry D. , Salopek Paul F. , Mahall Bruce E.
Published: January 2018

The differential germination responses of ray and disc achenes of Hemizonia increscens (Asteraceae) were compared in field and laboratory investigations in order to gain insight into the ecological and evolutionary significance of heterocarpy.

In the field, 200 ray and 200 disc achenes were placed in native, sterilized soil in a series of cleared, randomized, replicated plots. In a nearby plot a similar number of achenes were placed in plastic petri dishes in which high moisture conditions were maintained. Disc achene germination occurred under relatively minimal moisture conditions (<1 cm rainfall for 19 days) and relatively mild temperature regimes (21–7 C). Disc achene germination began three days after planting in the field plot and four days after they were put into the field petri dishes. In contrast, the onset of ray achene germination occurred 21 days after planting in the field plot and 19 days after planting in the field petri dishes. Averages of 2.05 and 2.71 disc achenes/day germinated in the field plot and field petri dishes, respectively. These contrasted with averages of 0.57 and 0.50 ray achenes/day germinated in the field plot and in the field petri dishes, respectively. A total of 67.5% and 69% disc achenes germinated in the field plot and the field petri dishes, but only 18% and 16.5% ray achenes germinated in the field plot and field petri dishes, respectively.

Three separate treatments, using 100 ray and 100 disc achenes in each, were performed in laboratory growth chambers: 1) nicking the fruit coat, 2) excising the embryo, and 3) leaving the fruit coat intact. Onset of germination for all disc achene treatments occurred after three days. No significant differences were found among the three disc achene treatments in timing, rate, or germination percentage. All three disc treatments in the laboratory closely paralleled those for disc achenes in the field plots in time and germination percentage, but rates of germination were not as high. Germination of the nicked and excised ray achenes treatments began after four days, while germination of the untreated ray achenes began after 27 days. Untreated ray achenes in the laboratory paralleled the ray achenes in both field experiments in rate and germination percentage, but were delayed in time of germination. The nicked and excised ray achene treatments, however, were similar to the disc achene treatments in time of germination, and were not significantly different from disc achenes in rate of germination. These data suggest 1) that ray and disc achenes are markedly different in germination under identical conditions in field and laboratory experiments, and 2) this difference in germination response may be due to the thicker pericarp of the ray achenes.
WILD GAMETOPHYTES OF PHANEROSORUS MAJOR (MATONIACEAE)
Authors: Yoroi Reiko , Kato Masahiro
Published: January 2018

The gametophytes of Phanerosorus major collected from wild populations in Seram Island are described. Young gametophytes are slender, ribbon‐like and uniformly one cell thick. They develop to old gametophytes with a broad thick cushion and coarsely ruffled wings. The gametophytes are monoecious and protandrous, although archegonia‐bearing thalli occasionally become antheridia‐bearing. Massive antheridia form on the ventral surface of young and old gametophytes while archegonia are borne on the cushion of old ones. Both young and old gametophytes reproduce vegetatively. The gametophytic characters are compared with those of Matonia. The life cycle of P. major is discussed with reference to its ecology.
CRYPTIC SELF‐INCOMPATIBILITY AND THE BREEDING SYSTEM OF CLARKIA UNGUICULATA (ONAGRACEAE)
Authors: Bowman Robert N.
Published: January 2018

Analysis of 2,117 segregating progeny from competitive pollinations involving self and foreign pollen reveals that Clarkia unguiculata possesses a cryptic self‐incompatibility mechanism. This mechanism promotes outcrossing when foreign pollen is available, yet allows for high fecundity through selling in marginal or catastrophically reduced populations. Competitively based self‐incompatibility in the species suggests that discrimination against genetically similar siblings may also be possible. The preferential self‐exclusion system insures that a seed crop of maximal size and genetic heterogeneity will be produced despite unpredictable environmental perturbations.
MECHANISMS OF APOMIXIS IN ELYMUS RECTISETUS FROM EASTERN AUSTRALIA AND NEW ZEALAND
Authors: Crane Charles F. , Carman John G.
Published: January 2018

Megasporogenesis was examined in cleared ovaries of 23 accessions of hexaploid Elymus from southeastern Queensland, northeastern New South Wales, the Australian Capital Territory, and the South Island of New Zealand. Apomixis was confined to the 17 accessions that morphologically corresponded to E. rectisetus (Nees in Lehm.) Löve et Connor. Female meiotic development followed the Polygonum type. Apomeiotic development was delayed relative to meiotic development because of a lengthy period of MMC vacuolation and nuclear stretching that occurred in place of meiosis I. Amitosis was evident in up to possibly five percent of the MMC's during nuclear stretching. A subsequent mitotic division facultatively functioned as meiosis II or the first embryo‐sac mitosis to yield a 2n megaspore dyad, a hemidyad with an incomplete crosswall, or a directly binucleate embryo sac. Nuclear stretching generally resumed in the chalazal daughter nucleus from the apomeiotic division, but was not seen later in embryo sac development. When a dyad formed, its chalazal member would enlarge and develop into the embryo sac. The organized embryo sac was of the conventional eight‐nucleate, seven‐celled structure prior to antipodal proliferation, regardless of meiotic or apomeiotic origin. Microsporocyte meiosis was normal in both sexuals and apomicts. Deposition of a slightly birefringent substance, possibly callose, was deficient around megasporocytes, megaspores, and microsporocytes in the apomicts.
PARAMETERS OF FILAMENT ELONGATION IN IPOMOEA NIL (CONVOLVULACEAE)
Authors: Koning Ross E. , Raab Mandy M.
Published: January 2018

It has been thought for some time that morning glory filaments elongate in response to changes in concentrations of gibberellins (Murakami, 1973), but many other aspects of their growth have remained unstudied. In the present work, the interacting roles of gibberellin and ethylene in filament growth were examined. Filaments elongated ten‐fold by epidermal cell elongation accompanied by ten‐fold increases in fresh and dry weight. Applied gibberellins could stimulate filament growth in vitro, but gibberellin biosynthesis inhibitors had no effect. The putative gibberellin action inhibitor, ancymidol, reduced growth but the inhibition could be removed by blocking ethylene biosynthesis. Stimulators of the ethylene biosynthesis pathway and applied ethylene precursor (ACC) strongly inhibited filament elongation; ethylene biosynthesis inhibitors elicited as much growth as applied gibberellin. The filaments produced little ethylene at the time of the onset of growth. While the filaments produced ethylene rapidly before and after growth initiation, the closed flower bud had a relatively constant level of ethylene. It seems likely that in situ production of ethylene negatively influences filament growth.
STRUCTURALLY PRESERVED FOSSIL PLANTS FROM ANTARCTICA III. PERMIAN SEEDS
Authors: Taylor Thomas N. , Taylor Edith L.
Published: January 2018

Small, anatomically preserved gymnospermous seeds are detailed from late Permian age silicified specimens collected in the Beardmore Glacier region of Antarctica. The seeds are platyspermic with prominent, sarcotestal wings and a simple pollen chamber. The integument consists of a narrow endotesta, a two‐parted sclerotesta and a complex sarcotesta. In mature seeds, the nucellus is present as a papery layer, separated from the endotesta by a nucellar and endotestal cuticle. Cellular megagametophytes are present in many of the seeds and commonly contain two archegonia. A multicellular embryo is present within each archegonium. The embryos are at a similar stage of development and provide evidence of simple polyembryony in these seeds. Although the affinities of the seeds are not presently known, they are discussed in the context of other seeds described from Gondwana deposits, as well as the known flora from the Beardmore Glacier area.
INTERACTING ROLES OF GIBBERELLIN AND ETHYLENE IN COROLLA EXPANSION OF IPOMOEA NIL (CONVOLVULACEAE)
Authors: Raab Mandy M. , Koning Ross E.
Published: January 2018

The relatively rapid and extensive corolla expansion in Ipomoea nil (L.) Roth cv. ‘Scarlett O'Hara’ appears to be initiated by a shift in the balance between a growth promoter (gibberellin, GA) and a growth inhibitor (ethylene) two days before anthesis. The effects of applied growth regulators in vitro, were measured as a change in area of segments from whole young corollas 16–17 mm long. Applied gibberellic acid (GA3) strongly promoted growth, while a GA action inhibitor (ancymidol) reduced growth. Inhibitors of GA biosynthesis (AMO‐1618, paclobutrazol, tetcyclasis, and chlorocholine chloride) had little effect, implying that the GAs were not being synthesized within the corolla segments, at least at this stage of corolla growth. Both the level of endogenous GAs and response of the segments to sucrose increased as the corolla size also increased from 15 to 20 mm in length. Applied 1‐aminocyclopropane‐l‐carboxylic acid (ACC), an ethylene precursor, inhibited the response of corollas to applied GA3. Applications of ethylene biosynthesis inhibitors (AVG and cobalt ions) promoted growth of the corolla segments. Rapid ethylene production by corollas 15–17 mm long (48 hr before flower opening) appeared to inhibit the growth that may have been induced by low levels of endogenous GAs. Older corollas (longer than 18 mm) had very low levels of ethylene production and much higher levels of GA‐like substances; these changes apparently allow the corollas to begin to expand in vivo and to strongly respond to sucrose applications alone in vitro. Acid‐induced growth does not seem to be an important component of corolla expansion; applied fusicoccin (a proton efflux promoter) and sodium orthovanadate (a proton efflux inhibitor) had no significant effect on growth of the 16–17 mm long corollas. Buffers (Good's and phosphate) over a wide pH range had no effect on corolla expansion. Taken together, our results indicate that the regulation of corolla expansion depends (at least in part) on compensatory shifts in the levels of two plant growth regulators [PGRs], ethylene and GA.
ORIGIN OF SEED PLANTS: AN ANEUROPHYTE/SEED‐FERN LINK ELABORATED
Authors: Rothwell Gar W. , Erwin Diane M.
Published: January 2018

Gymnosperm‐like stem and frond fragments have been discovered in the same Devonian deposits of West Virginia that yield the most ancient seeds. The vegetative organs exhibit the stem/leaf differentiation and frond structure that are characteristic of seed ferns, but they have a stelar configuration and a protoxylem architecture that are most similar to aneurophytalean progymnosperms. This combination of features supports the hypothesis that aneurophytalean progymnosperms are ancestral to gymnosperms.
DYNAMICS OF POLLEN TUBE GROWTH IN THE WILD RADISH RAPHANUS RAPHANISTRUM (BRASSICACEAE). II. MORPHOLOGY, CYTOCHEMISTRY AND ULTRASTRUCTURE OF TRANSMITTING TISSUES, AND PATH OF POLLEN TUBE GROWTH
Authors: Hill Jeffrey P. , Lord Elizabeth M.
Published: January 2018

The relative importance of prezygotic mechanisms of gametophytic competition and selection are often unclear due to an absence of observations on the gynoecium and pollen tube growth in vivo. We used LM, SEM, and TEM to study the structure of the gynoecium and the path of pollen tube growth in Raphanus raphanistrum, a sporophytically self‐incompatible annual.

Wild radish has a papillate stigma and a solid style. A septum, which is characteristic of cruciferous gynoecia, is present in the ovary. After germination on the stigma, pollen tubes grow in the secretion of the transmitting tract of the style. The stylar secretion stains positive for acidic polysaccharides and insoluble carbohydrates, and negative for lipids and protein. In the ovary, the transmitting tissue is contained inside the septum. The secretion in the ovary stains positive only for acidic polysaccharides. Pollen tubes travel inside the septum as they enter the ovary and must exit to the surface of this tissue before ovule fertilization can occur. Pollen tube growth on the septum tracks the intercellular junctions of the septum epidermis where the secretion leaks out through a torn cuticle. Tubes must grow across the obturator before reaching the micropyle of an ovule. The temporal pattern with which tubes growing into the ovary exit the septum can contribute to the previously observed nonrandom patterns of fertilization (Hill and Lord, 1986).
POLLEN MORPHOLOGY IN THE GENUS ERYTHRONIUM (LILIACEAE) AND ITS SYSTEMATIC IMPLICATIONS
Authors: Takahashi Masamichi
Published: January 2018

Pollen morphology was examined in 40 samples from 19 species in the genus Erythronium (Liliaceae) using scanning (SEM) and transmission electron microscopy (TEM). Pollen grains are monosulcate monads, except for a plant of E. oregonum which has dyad grains. North American and European species are characterized by reticulate exine sculpture composed of various degrees of wavy muri and variably‐sized lumina. The most distinctive feature of exine sculpture in the genus is exhibited by the Asian species E. japonicum, which has a unique reticulate pattern composed of striate muri and a distinctive exine structure without columellae. The distinctness of E. japonicum pollen suggests that it has specialized in isolation from species in North America and Europe.
PROTOPLAST FUSION: A NOVEL APPROACH TO ORGANELLE GENETICS IN HIGHER PLANTS
Authors: Kumar Amar , Cocking Edward C.
Published: January 2018

In the majority of higher plants there is maternal inheritance of cytoplasmic organelles and, as a consequence, there are few opportunities for the study of the effects on plant phenotype of having cytoplasm initially containing organelles of both parents. Now the availability of somatic plant protoplasts, which can be fused together and suitably cultured to produce somatic hybrid plants, is enabling the effects of such hybrid cytoplasms to be investigated in higher plants exhibiting maternal inheritance. A very wide range of cytoplasmic genetic diversity, including mitochondrial and chloroplast recombinants, can be produced by such somatic hybridizations, and a theoretical model is presented to show the origins of this wide range of cytoplasmic diversity. Cybrids produced by such protoplast fusions have been shown to be of importance in plant breeding especially in relation to transfer of cytoplasmic male sterility and herbicide resistance. Protoplast fusion, including the fusion of gametic and somatic protoplasts, is also enabling the study of the inheritance of cytoplasmic controlled traits in higher plants.
OSMOPHORES OF STANHOPEA (ORCHIDACEAE)
Authors: Stern William Louis , Curry Kenneth J. , Pridgeon Alec M.
Published: January 2018

Species of the Neotropical orchid genus Stanhopea produce a fragrance comprising terpenoids and aromatics which attracts euglossine bee pollinators. The secretory tissue, called an osmophore, is located in the adaxial region of a sac formed near the proximal portion of the floral lip. This region is easily recognized in Stanhopea oculata and S. wardii because it is papillate. The osmophore in these two species includes all the cells of the papillae and those directly below, that grade into fundamental tissue. Osmophore cells are more densely cytoplasmic than cells in the adjacent tissue. Numerous amyloplasts and mitochondria are seen in these cells from the earliest bud stages we examined through anthesis. Smooth and rough endoplasmic reticulum are abundant, but dictyosomes are uncommon. Mitochondria of osmophore cells appear to be distributed with no apparent pattern during bud stages, although they tend to be aligned near the plasmalemma at anthesis. Osmophore cells are highly vacuolate after anthesis.
RELATIONSHIP OF WOODY PARTHENIUM ARGENTATUM AND HERBACEOUS P. HISPIDUM VAR. AURICULATUM (ASTERACEAE)
Authors: Hashemi Ahmad , Estilai Ali , West Jan E. , Waines J. Giles
Published: January 2018

Interspecific hybrids between woody Parthenium argentatum Gray (guayule), native to Mexico and Southwest Texas, and herbaceous perennial P. hispidum var. auriculatum (Britton) Rollins, native to the United States, were obtained successfully. The F1 hybrids were intermediate for most morphological characters with the exception of the short woody stem, yellow pollen color, and the trichome morphology. Chromosome counts revealed the presence of 2n = 36 A‐chromosomes in P. argentatum. The same number of A‐chromosomes and four B‐chromosomes were found in P. hispidum var. auriculatum. Observations of pollen mother cells showed regular meiosis in both parental species. At diakinesis, chiasmata averaged 1.12 and 1.24 per bivalent for P. argentatum and P. hispidum var. auriculatum, respectively. Meiotic behavior of the F1 hybrids was irregular. F1 hybrids averaged 4.43 univalents at metaphase I, 1.95 laggards at anaphase I, and 1.62 micronuclei at the tetrad stage. The low pollen stainability (5.1%) in the F1 hybrids and the limited number of viable BC1 seeds (4.07%) may be reflections of the irregular meiosis. Although these primary hybrids are partially fertile, they can be used to introduce desirable characteristics of P. hispidum var. auriculatum, such as herbaceous perennial habit, regrowth ability, and cold tolerance into guayule.
PATTERNS OF FLORAL DEVELOPMENT IN AGALINIS AND ALLIES (SCROPHULARIACEAE). II. FLORAL DEVELOPMENT OF AGALINIS DENSIFLORA
Authors: Canne‐Hilliker Judith M.
Published: January 2018

Initiation of floral primordia begins in Agalinis densiflora with production of two lateral adaxial calyx lobe primordia followed by a midadaxial primordium, and then primordia of two abaxial calyx lobes. Initiation of three abaxial corolla lobe primordia is succeeded by that of two stamen pairs and then by primordia of two adaxial corolla lobes. The primordium of the abaxial carpel appears before the adaxial one. Except for the calyx, initiation of primordia proceeds unidirectionally from the abaxial to the adaxial side of the floral apex. Zygomorphy in the calyx, corolla, and androecium is evident during initiation of primordia and is accentuated during organogenesis. The calyx undergoes comparatively rapid organogenesis, but the inner three floral series undergo a protracted period of organogenesis. The perianth series reach maturation prior to meiosis in the anthers. Maturation of the androecium and gynoecium are postmeiotic events.