bluuebunny/crossref_metadata_2025 huggingface dataset:
CENTRUM DEVELOPMENT IN DIDYMELLA BRYONIAE
Authors: Skarshaug A. J.
Published: January 2018

Early stages of pseudothecium development consist of small pseudoparenchymatous stromata in which ascogonia differentiate. Deeply staining cells in the apical region of the young pseudothecium elongate to form pseudoparaphyses, which grow down to fill the centrum. Ascogenous hyphae grow out from ascogenous cells, located in the basal plectenchyma, and croziers arise and proliferate from the ascogenous hyphae. Bitunicate asci grow up among the pseudoparaphyses and forcibly discharge two‐celled hyaline ascospores at maturity. Because centrum development in Didymella bryoniae (Auersw.) Rehm is pseudoparaphysate, the causal agent of gummy stem blight in watermelon is properly placed in the order Pleosporales. The placement of this species in Didymella on the basis of the Ascochyta cucumis Fautr. et Roum. anamorph is supported by centrum structure.
THE FLORAL AND EXTRA‐FLORAL NECTARIES OF PASSIFLORA. I. THE FLORAL NECTARY
Authors: Durkee Lenore T. , Gaal Dorothy J. , Reisner W. Howard
Published: January 2018

Floral nectary development and nectar secretion in three species of Passiflora were investigated with light and electron microscopy. The nectary ring results from the activity of an intercalary meristem. Increased starch deposition in the amyloplasts of the secretory cells parallels maturation of the nectary phloem. Large membrane‐bound protein bodies are observed consistently in phloem parenchyma cells, but their function is presently unknown. The stored starch serves as the main source of nectar sugars at anthesis. Plastid envelope integrity is maintained during starch degradation, and there is no evidence of participation of endoplasmic reticulum or Golgi in the secretion of pre‐nectar. It is concluded that in these starchy nectaries granulocrine secretion, commonly reported for floral nectaries, does not occur.
STRUCTURE AND DYNAMICS OF HARDWOOD SWAMPS IN THE NEW JERSEY PINE BARRENS: CONTRASTING PATTERNS IN TREES AND SHRUBS
Authors: Ehrenfeld Joan G. , Gulick Martha
Published: January 2018

The biomass, density, age structure, and dominance patterns of the tree and shrub populations in hardwood swamps of the New Jersey Pine Barrens are described and contrasted with each other. The total biomass of individual swamps ranges from 92,000 kg/ha to 194,000 kg/ha, depending on the age of the stand. These biomass values are similar to those reported for southern hardwood swamps. The Pine Barrens swamps are distinguished by very large populations of ericaceous and other shrubs, which range up to 13% of the total above‐ground biomass. The tree populations, composed principally of Acer rubrum, Nyssa sylvatica and Magnolia virginiana, are even‐aged; Acer is strongly dominating, with a minimum of 73% of the biomass, and species richness is associated with the availability of different microhabitats. The shrub populations, by contrast, are all‐aged, with the dominance patterns among the species and the stand biomasses varying with the degree of flooding of the stand. Differences in size and growth rate among the shrub species parallel their evident response to the flooding gradient. The shrub stratum has lower species richness than the comparable southern swamps and floodplains, but ranges up to higher biomass values.
SPATIAL AND AGE DEPENDENT PATTERNS OF GROWTH IN NEW ENGLAND BLACK BIRCH
Authors: Kirkpatrick Mark
Published: January 2018

Ring width chronologies from 127 black birch trees in the northeastern United States were used to study age dependent and spatial patterns in growth. The trees sampled show no evidence for increasing stability of growth with age, as measured by the year‐to‐year variance and autocorrelation. Large scale spatial patterns were studied using trees sampled from five localities separated by distances of 40 km to 325 km. Cluster analysis based on the last 30 years of growth is able to assign a tree to its locality of origin with approximately 80% accuracy. However, the degree of correlation between these chronologies does not decline as a function of the distance of separation of the localities. Fine scale patterns were studied using chronologies from 46 birches lying within a 50‐m x 60‐m plot. Strong neighborhood effects could not be detected in the rate of growth, the variance of growth, or the between‐tree correlation. Dry‐site trees, however, were found to be growing significantly faster and with less variability than wet‐site trees. The results suggest that very local factors are important determinants of growth and dominate the environmental structure perceived by mesic forest trees.
INCREASE IN SIZE AND CELL NUMBER OF LATERAL ROOT PRIMORDIA IN THE PRIMARY OF INTACT PLANTS AND IN EXCISED ROOTS OF PISUM SATIVUM AND VICIA FABA
Authors: Thompson Anne , MacLeod Ronald D.
Published: January 2018

Increase in cell number, and in anlage volume and length have been investigated during the development of lateral root primordia in roots of intact plants of Pisum sativum and Vicia faba and in excised roots of both species cultured in White's medium supplemented with 2% sucrose. With the exception of primordia in excised roots of Vicia, the general equation which best described increase in each aspect of primoridium growth measured against time was that for exponential growth. When the times necessary for cell number and primordium volume and length to double were determined at intervals over the period of development studied, however, they were found to vary. Similarly, estimates of the size of the proliferative fraction of cells at different times during anlage development indicated that this index of meristematic activity also fluctuated over the developmental period investigated, i.e., increase in cell number and in primordium volume and length do not occur in a truly exponential fashion as the primordia increase in size and cell number.

One difference between anlage development in the roots of intact plants and in those grown in culture was that whereas the former primordia completed their development and emerged as lateral roots over the period of the investigation, the latter did not. Moreover, cell doubling time and anlage volume and length doubling times were longer, and the proliferation fraction of cells lower, over the whole period of, and at intervals during, primordium development in the excised roots compared with the results obtained for the roots of the corresponding intact plants.
ISOLATION OF N‐PARAFFIN HYDROCARBONS FROM PSEUDOTSUGA MACROCARPA
Authors: Scora Rainer W.
Published: January 2018

Normal paraffin hydrocarbons of Pseudotsuga macrocarpa Mayr. collected from eight sites in California were compared with each other and with those of P. menziesii (Mirb.) Franco collected from two locations. Quantitative differences within the first species could not be correlated with geographic location. However, both the species could be separated completely on the basis of their (C30H62) triacontane content.
THE EFFECT OF METHANOL ON SPORE GERMINATION AND RHIZOID DIFFERENTIATION IN ONOCLEA SENSIBILIS
Authors: Vogelmann Thomas C. , Miller John H.
Published: January 2018

In germinating spores of Onoclea sensibilis, the nucleus migrates to one end prior to an asymmetric cell division that partitions each spore into two daughter cells of unequal size. The larger cell develops into a protonema, whereas the smaller cell immediately differentiates into a rhizoid. When spores were germinated in the presence of methanol, nuclear migration was inhibited and most nuclei moved only to the raphe on the proximal side of the spores. Subsequent cell division partitioned each spore into daughter cells of equal size of which both developed into a protonema and neither into a rhizoid. Spores became sensitive to methanol at a time just prior to or coincident with nuclear migration and the effects of the alcohol were rapidly reversible as long as the spores were removed from methanol prior to the completion of cell division. Exposure to methanol prior to, but not during, nuclear migration or after mitosis had no effect upon rhizoid differentiation. The alcohol disrupted the formation of crosswalls after mitosis and they were often convoluted and irregularly branched. These results are consistent with the interpretation that methanol may disrupt a membrane site that plays an essential role in nuclear movement and rhizoid differentiation.
SOMATIC CELL INCOMPATIBILITY IN DIDYMIUM IRIDIS: LOCUS IDENTIFICATION AND FUNCTION
Authors: Ling Hubert , Clark Jim
Published: January 2018

Somatic incompatibility in two strains of the myxomycete Didymium iridis is controlled by at least 13 loci: seven fusion loci and six clear‐zone loci. Details on correlating loci of the Hon 1 strain with Pan 1 loci are given and a unified nomenclature, applicable to both strains, has been developed from data presented in this paper. Although fusion loci generally prevent fusion between different plasmodial incompatibility phenotypes, studies on individual loci have shown that a limited transient fusion may occasionally take place. Thus, the differences between the fusion and clear‐zone loci are not as distinct as once thought. However, the 13 somatic incompatibility loci are still easily designated as either fusion or clear‐zone loci, and no locus has thus far been found with true intermediate function. Studies on individual locus function are also discussed.
ANT‐POLLINATION OF THE GRANITE OUTCROP ENDEMIC DIAMORPHA SMALLII (CRASSULACEAE)
Authors: Wyatt Robert
Published: January 2018

Formica schaufussi, a medium‐sized ant common throughout the Piedmont and Coastal Plain of the southeastern United States, has been observed in association with Diamorpha smallii, a self‐incompatible annual endemic to granite outcrops in the Southeast, over a 6‐yr period. Observations of ants collected on the flowers show large numbers of the sticky pollen grains adhering to hairs and indentations primarily on the thoraces of the ants. Though small native bees and flies are frequent and sometimes effective pollinators, it is highly unlikely that the monotypic genus Diamorpha coevolved with the introduced honeybee, as has been suggested. Characteristics indicative of an “ant‐pollination syndrome” include occurrence in hot, dry habitats, a high density of very small plants bearing overlapping inflorescences at a uniform height, and low seed number, pollen volume, and nectar quantity.
REPRODUCTIVE ISOLATION BARRIERS TO GENE EXCHANGE BETWEEN SOLANUM CHACOENSE AND S. COMMERSONII (SOLANACEAE)
Authors: Summers Dennis , Grun Paul
Published: January 2018

In contrast to the general intercompatibility of diploid species of tuber‐bearing potatoes of South America, Solanum chacoense Bitter and S. commersonii Dunal have well‐established internal barriers to gene exchange. Pollen tubes of S. commersonii are inhibited in growth down the style of S. chacoense. While S. chacoense pollen tubes are not inhibited in S. commersonii stylar tissue, seed development is abnormal, resulting in production of large numbers of seeds that are not filled out. Even the apparently normal F1 seed germinated poorly; approximately 0.1 germinable seeds were set per cross as compared with over 30 seeds per cross following intraspecific crosses. Lowland S. chacoense, including populations sympatric with S. commersonii, were not more effectively isolated from S. commersonii than were highland S. chacoense populations, over 500 km from the nearest S. commersonii. The F1 hybrids produced were vigorous and highly fertile. Crosses between unrelated S. commersonii‐chacoense F1 hybrids produced only 1.3 germinable seeds per cross. This reduction resulted from low numbers of berries set, few seeds per berry, and low seed germination.

The F2 progeny were vigorous, but while many were both male and female fertile there were indications of an increase in sterility over that of the parents and F1's. The data were interpreted as indicating that the isolation barriers result from polygenic differences between the parent species and are composed principally of genes that function in several of the processes of seed setting. The accumulation of genes that keep these species isolated was interpreted as not having developed as a result of selection for such isolation in the region of overlap (Wallace effect), but rather as a byproduct of divergence that occurred during their allopatric evolution.
AN ECOLOGICAL COMPARISON OF UPLAND DECIDUOUS AND EVERGREEN FORESTS OF CENTRAL TEXAS
Authors: Van Auken O. W. , Ford A. L. , Allen J. L.
Published: January 2018

Scrub evergreen forests cover most of the cedar breaks region of the Edwards Plateau of central Texas; however, limited strips of deciduous forests are found on north‐facing slopes just below the limestone caprock. Dominant species occurring in the deciduous forests in descending order of importance include Quercus texana, Q. glaucoides, Juniperus ashei, Diospyros texana, Prunus serotina, Aesculus pavia, Juglans nigra, and Fraxinus texensis. Nineteen woody species were found in the deciduous forests. Forty‐eight percent of the species were exclusive to the deciduous forest community. The deciduous forests had a statistically greater number of species/stand and a higher density. The deciduous species found in the strip forests had combined relative density, dominance and importance values of 59, 93 and 72%, respectively. Dominants in the evergreen forest were J. ashei and D. texana, which had relative density, dominance, and importance values totaling 90, 97 and 93%, respectively. Total dominance was the same for both communities; however, J. ashei dominance was 20 times higher in the evergreen forests. Soils of the deciduous forests were significantly deeper and rockier. Also, these soils had higher organic contents and water retention capacities. The potential field capacity (PFC) was 3.47 times higher for the deciduous forest soils resulting in a 2.36‐fold increase in the water availability index (WAI). Factors regulating distribution and composition of the deciduous forest communities appear to be insolation and PFC, resulting in part from differences in topographic position.
GERMINATION AND SEEDLING GROWTH IN ECHINOCHLOA CRUS‐GALLI VAR. ORYZICOLA UNDER ANOXIC CONDITIONS: STRUCTURAL ASPECTS
Authors: VanderZee Delmar , Kennedy Robert A.
Published: January 2018

The morphological and cellular basis of anoxic germination in Echinochloa crus‐galli var. oryzicola is reported. The embryo of E. crus‐galli var. oryzicola is typically panicoid in its overall morphology, and is relatively large with a prominent coleoptile and mesocotyl. The response to anoxia is essentially the same in light and dark. Shoot growth occurs in both mesocotyl and coleoptile by cell elongation with no cell division. There is no emergence of the radicle without oxygen. Under anoxia the growth response is not the same as etiolation; there is no plumule elongation within the coleoptile, no protochlorophyll(ide) is found, and limited mesocotyl elongation occurs without oxygen. Air‐dark treatment after anoxic germination results in a typical etiolated morphological response, including a resumption of mesocotyl growth, elongation of the plumule within the coleoptile, and initiation of pigment synthesis. These results indicate the effects of anoxia are not permanent but rather limiting and reversible.
IS TRIGONELLINE A PLANT HORMONE?
Authors: Evans Lance S. , Tramontano William A.
Published: January 2018

Experimental results are presented so that trigonelline may be evaluated as a plant hormone. Trigonelline promotes preferential cell arrest in G2 of the cell cycle for about 40% of the cell population in root meristems of Pisum sativum. Trigonelline is present in ungerminated seeds and is transported from cotyledons to other tissues during early seedling development. These experimental results show that trigonelline satisfies all six criteria that have been used to establish whether a substance is a hormone. As the seedlings age from day 3 to 10, the concentration of trigonelline in meristems decreases and so does the proportion of cells arrested in G2. Trigonelline may be isolated from excised cotyledons and can be added back to decotyledonized seedlings or excised root meristems to have the same effect as found in intact organisms. Predominant cell arrest in G2 occurs in roots of some plant species, although other species show preponderant cell arrest in G1. Many members of the Preiss‐Handler metabolic pathway show some ability to promote cell arrest in G2 but only at concentrations 100 (10‐5 m) or 1,000 (10‐4 m) times the concentration of trigonelline (10‐7 m) necessary for function. The proportion of cells arrested in G2 is highly correlated with the concentration of trigonelline within the root meristem.
THE ONE HUNDRED‐YEAR PERIOD FOR DR. BEAL'S SEED VIABILITY EXPERIMENT
Authors: Kivilaan A. , Bandurski Robert S.
Published: January 2018

After 100 years of burial in moist well aerated sand, 21 seeds of Verbascum blattaria, one seed of Verbascum thapsus and one seed of Malva rotundifolia, germinated and produced normal plants. Six additional seeds, of the original 50 seeds of each of 20 varieties, germinated and died before identification was possible.
CHANGES IN MEGAGAMETOPHYTE STRUCTURE IN PAPAVER NUDICAULE L. (PAPAVERACEAE) FOLLOWING IN VITRO PLACENTAL POLLINATION
Authors: Olson A. Randall , Cass David D.
Published: January 2018

Papaver nudicaule placentae with attached ovules were dissected out of unpollinated gynoecia 1–3 days after anthesis, dusted with pollen, and cultured on modified Nitsch's growth medium at 23 C. Ovules were removed from expiants at 15, 24, 31, and 48 hr postpollination, fixed in GA‐OsO4, embedded in Spurr's resin and sectioned (1.0 μm) for light microscopy. Placentae, 15 hr after pollination, were fixed and processed for scanning electron microscopy. Pollen germinates within 1 hr. Although most pollen tube growth appears random, there is directional growth toward the micropyle. The crassinucellate ovule contains an embryo sac consisting of three antipodals, two polar nuclei, and an egg apparatus composed of two synergids and a polarized egg having a large chalazal vacuole and micropylar nucleus. Pollen tube access into the megagametophyte is through a degenerate synergid, with fertilization occurring between 24 and 31 hr after pollination. Zygote establishment is accompanied by polarity reversal in which the nucleus assumes the chalazal position subtended by a large micropylar vacuole. Fertilized ovules normally develop into germinable seeds.
NEW TAXODIACEOUS SEED CONES FROM THE UPPER CRETACEOUS OF NEW JERSEY
Authors: LaPasha Constantine A. , Miller Charles N.
Published: January 2018

Nephrostrobus cliffwoodensis gen. et sp. nov., Nephrostrobus bifurcatus sp. nov., and Rhombostrobus cliffwoodensis gen. et sp. nov. are described based on anatomical studies of seed cone fragments from the Upper Cretaceous Magothy Formation of New Jersey. These species belong to the Taxodiaceae. As in Sequoia, Sequoiadendron. and Metasequoia, the vascular strands supplying the scale and bract in Nephrostrobus are about equal. These vascular strands are arranged in a reniform pattern resembling that found in Metasequoia, but the orientation differs by 180 degress. Nephrostrobus cliffwoodensis and Nephrostrobus bifurcatus differ from each other in the branching of the complex trace and associated resin canals. Rhombostrobus cliffwoodensis resembles Cunninghamia in the arrangement of vascular strands and associated resin canals in its bract‐scale complexes. However, the relative amount of bract and ovuliferous scale making up the complex is more like that in Sequoia. This combination of cone features does not occur in any of the extant genera. Nephrostrobus and Rhombostrobus are not considered to be ancestral to any of the extant taxodiaceous genera, but are extinct members of an ancestral complex from which the extant genera were derived.
CELLULAR SLIME MOLDS OF SWITZERLAND. I. DESCRIPTION OF NEW SPECIES
Authors: Traub Franz , Hohl Hans R. , Cavender James C.
Published: January 2018

During the study of the distribution of cellular slime molds in Swiss forest soils, three new species were isolated and studied in culture, namely, Dictyostelium fasciculatum, Dictyostelium polycarpum and Polysphondylium filamentosum. The first is cosmopolitan, the latter two are known only from Switzerland. Dictyostelium polycarpum is a very delicate species and is the first species reported which is restricted to a high altitude environment. It is characterized by a coremiform habit, reminiscent of D. polycephalum, and relatively long reniform spores. Dictyostelium fasciculatum is a larger species which resembles D. mucoroides in gross morphology but is much closer to Polysphondylium in its life cycle pattern and behavior. Polysphondylium filamentosum is only the third well‐defined species of the genus to be described. It produces filamentose principal and lateral axes. Optimum temperature for all three is around 20 C, somewhat below that of most other species in the family.
ULTRASTRUCTURAL LOCALIZATION OF ADENOSINE TRIPHOSPHATASE IN THE OVULES OF SAINTPAULIA IONANTHA (GESNERIACEAE) AND ITS RELATION TO SYNERGID FUNCTION AND EMBRYO SAC NUTRITION
Authors: Mogensen H. Lloyd
Published: January 2018

Ovules of African violet were analyzed for adenosine triphosphatase activity. Ovules from unpollinated flowers of three different ages were fixed in buffered, 3% paraformaldehyde, incubated in the Wachstein‐Meisel medium, and processed for electron microscopy. Results showed a heavy reaction product in the endothelium and inner micropylar cells of the integument with decreasing amounts elsewhere. Reaction product was localized primarily on the plasma membrane, and occasionally in the nuclear membrane, endoplasmic reticulum, small vacuoles, and mitochondria. The synergids, egg, central cell, and antipodals were essentailly devoid of reaction product except for rare occurrences in the smaller vacuoles and mitochondria of the synergids, and fragmentary deposits on the plasma membrane of the antipodals. No differences were found in any of the floral stages examined. These results suggest that the integumentary cells nearest the embryo sac are equipped with the necessary enzymes for active translocation of solutes into the embryo sac and that the cells of the megagametophyte apparently function more passively in this regard.
THE COMPARATIVE AND DEVELOPMENTAL MORPHOLOGY OF THE ROOT SYSTEM OF SELAGINELLA SELAGINOIDES (L.) LINK
Authors: Karrfalt Eric E.
Published: January 2018

All of the roots of Selaginella selaginoides are attached laterally to the base of the shoot, which has monopolar growth as is characteristic of Selaginella. The first three roots are produced by meristematic activity in the cortex of the hypocotyl as in several other species of Selaginella. The fourth root is produced in the same way as the first three, except that not all of the cortical cells which become meristematic mature into root tissue. Some of the meristematic tissue remains undifferentiated and continues to produce additional roots. Potentially an unlimited number of roots could be produced, but no plant was found to have more than eight. There is some secondary growth in the cortex of the basal swelling on the hypocotyl, but no secondary vascular tissue is produced and no cambium of any sort is ever organized. On the basis of comparisons with other living species of Selaginella. the centralized root system of S. selaginoides is interpreted as having been modified from a noncentralized type of root system by the persistence of the juvenile mode of root production.
IMMUNOCHEMICAL COMPARISONS OF SEED PROTEINS FROM POPULATIONS OF PINUS RADIATA (PINACEAE)
Authors: Murphy Terence M.
Published: January 2018

Antisera were prepared to seed proteins from five populations of Pinus radiata and to seed proteins from six other pine species. Differences between the P. radiata populations detected with these antisera were compared to differences in sizes of cones from the same populations. The strong correlation between antigenic differences and cone size differences provides evidence that in P. radiata, both seed proteins and cone size indicate quantitative genetic relationships among the populations. The data suggest that the three California mainland populations of P. radiata are more closely related to one another than to the insular populations, and that the insular populations are more closely related to each other than to the California populations, to P. attenuata, or to P. muricata.
STRUCTURE AND ONTOGENY OF THE STOMATAL COMPLEX IN PINUS STROBUS L. AND PINUS BANKSIANA LAMB.
Authors: Johnson R. W. , Riding R. T.
Published: January 2018

The morphology of the stomatal complex in Pinus strobus L. and P. banksiana Lamb, is described and it is proposed that the stomatal complex should be considered an eight‐celled complex consisting of two guard cells, and two polar, two lateral, and two hypodermal subsidiary cells. An ontogenetic study found these cells closely related developmentally. It was also found that the stomatal complex in these two pines could not readily be classified as haplocheilic because a polar subsidiary cell arises from the same protodermal cell as does the guard cell mother cell. A modification of the classical concept of stomatal development was necessary to describe the stomata as eumesoperigenous.
DISPERSAL ABILITIES OF SEVEN SPARSE AND COMMON GRASSES FROM A MISSOURI PRAIRIE
Authors: Rabinowitz Deborah , Rapp Jody K.
Published: January 2018

Seven grass species on an abundance continuum from common to sparse on a Missouri tall‐grass prairie were examined for two diaspore traits (morphology and weight), for three dispersal traits (terminal velocity, and mean and maximum lateral movement propagules released in still air from a height of 1 m), and for two parental traits (culm biomass at maturity and culm height at dispersal). Dispersal ability, measured in the laboratory as the lateral movement of propagules in the upper 5% (right tail) of the distribution of distances, is inversely correlated (rs = –0.94) with biomass abundance. Under constant conditions, seeds of sparse species travel farther than seeds of common species. Dispersal ability is more closely related to a populational attribute (abundance) than to a more proximate characteristic (diaspore weight). Diaspore weight is closely related (rs = 0.97) to culm biomass of the parent, in apparently simple allometry, and more weakly related (rs = 0.71) to biomass abundance. Large parents make large seeds. The sparsest species, which is small in stature, has light (0.08 to 0.19 mg), flattened diaspores with low terminal velocities (82 to 87 cm sec−‐1) and achieves lateral movement (up to 460 mm) by tumbling and gliding. Species of intermediate abundance have intermediate stature and diaspore weight (1.0 to 1.8 mg), unornamented propagules, high terminal velocities (191 to 209 cm sec−‐1) and intermediate dispersal ability (up to 388 mm). The three most common species have heavy propagules (2.2 to 2.8 mg), ornamented with long hairs. Although the ornamentation slows fall (96 to 194 cm sec−‐1), it acts as a “guide parachute,” orienting the propagule so that it falls nearly straight downward. The common species, which morphologically appear adapted to longer dispersal, achieve little lateral movement (up to 235 mm) under laboratory conditions. Terminal velocity is a misleading descriptor of dispersal because diaspores with similar terminal velocities have differing movement patterns. When diaspores of two species (one tall common species and one short sparse species) are released in still air from their natural height, differences in maximum fall distance observed under constant height of release are lost. When dispersal is observed in the field by means of sticky seed traps, the slopes of the dispersal curves (regression coefficient of ln‐transformed number of seeds caught on distance from the clump) do not differ from common and sparse species, despite the fact that seeds of the common species are released from greater heights. The orderly differences in dispersal behavior among species due to subtleties of morphology observed under laboratory conditions are masked in nature.
EPIDERMAL FEATURES AND SILICA DEPOSITION IN LEMMAS AND AWNS OF ZIZANIA (GRAMINEAE)
Authors: Terrell Edward E. , Wergin William P.
Published: January 2018

In four species of Zizania (Gramineae: Oryzeae) epidermal features of pistillate and staminate lemmas, paleas, and awns were studied by scanning electron microscopy (SEM) and energy dispersive X‐ray analysis. Features observed were silica bodies, siliceous papillae, pitted siliceous papillae, stomata, microhairs, and prickle hairs. Staminate lemmas have all of these features. Pistillate lemmas have silica bodies and prickle hairs, lack stomata, and differ among species in occurrences of microhairs and siliceous papillae and pitted siliceous papillae. Awns of pistillate lemmas have silica bodies, prickle hairs, microhairs, and stomata; therefore, they possess a more complete set of features than their attached lemmas. Shapes of silica bodies on pistillate lemmas differ among species. A taxonomic key based on SEM observation of pistillate lemmas separates the four species by the shapes of silica bodies, arrangement of prickle hairs, and occurrences of microhairs and siliceous papillae. The main silica‐containing structures are silica bodies, siliceous papillae, pitted siliceous papillae, and to a lesser extent prickle hairs. Pitted siliceous papillae with circular raised rims are formed by collapse or exfoliation of the tops of siliceous papillae; these have not been previously described in grasses. Comparison of epidermal features in the lemmas and leaves of Zizania shows that the former lack three kinds of nonsilicified papillae and epicuticular wax that are present on the latter but the lemmas have siliceous papillae and pits that are absent in leaves.
CYTOCHEMICAL LOCALIZATION OF CELLULASE ACTIVITY IN ARTICULATED, ANASTOMOSING LATICIFERS OF PAPAVER SOMNIFERUM L. (PAPAVERACEAE)
Authors: Nessler Craig L. , Mahlberg Paul G.
Published: January 2018

Cellulase activity was localized at the ultrastructural level in the articulated, anastomosing laticifers of Papaver somniferum. Electron‐dense crystalline deposits indicating the presence of cellulase activity were restricted to discrete patches along the laticifer wall in regions of recently formed perforations. This report presents the first direct evidence for the involvement of cellulases in the cell wall perforation process in articulated laticifers.
TYPES OF CAMBIAL ACTIVITY AND WOOD ANATOMY OF STYLIDIUM (STYLIDIACEAE)
Authors: Carlquist Sherwin
Published: January 2018

Three types of cambial activity, two hitherto unreported, are described for Stylidium. The four species of sect. Rhynchangium of subgenus Nitrangium have woody cylinders in upright stems. In these a cambium formed beneath the endodermis produces a determinate quantity of fibers, vessel elements, and interxylary phloem strands toward the inside but no derivatives toward the outside; this was correctly reported by Van Tieghem and Morot (1884a) but doubted by subsequent workers. The same species have lignotubers in which a cambium produces contorted xylem (mostly vessels) to the inside, phellem toward the outside. In S. glandulosum and S. laricifolium a cambium formed beneath the endodermis produces an indeterminate quantity of xylem (fibers and vessel elements) and interxylary phloem toward the inside, nothing toward the outside. The xylem is rayless and lacks axial xylem parenchyma. These three modes of cambial activity represent innovations within Stylidiaceae. The family has a wholly herbaceous ancestry if one can judge from the total lack of cambial activity in vascular bundles.
THE ROLE OF SEED BANKS IN THE PERSISTENCE OF ONTARIO'S COASTAL PLAIN FLORA
Authors: Keddy P. A. , Reznicek A. A.
Published: January 2018

Seed banks are important in wetland vegetation, but their role on lakeshores has received little attention. The influence of seed banks on lakeshore vegetation was investigated near eastern Georgian Bay in Ontario, where there is a rich shoreline and aquatic flora. Some lakeshore species found there can be considered “coastal plain disjuncts” similar to those of southwestern Michigan and adjacent Indiana, and central Wisconsin. Matchedash Lake in Simcoe Co., Ontario, has a particularly rich assemblage of these shoreline species. Based on short‐term records, and aging of drowned stumps, we demonstrated that yearly mean water levels can and have changed by more than a meter. Such water‐level fluctuations partly result from beaver dams on the single outlet stream. Vegetation data collected in a low‐water phase (1976) document a rich shoreline flora, largely absent in the present (1979) high‐water phase. During this latter high‐water phase, we collected 15 sediment sample units from each of six water depths (0–1.5 m). The sample, representing 0.32 m2of lake bottom, was planted out in a greenhouse; 3,149 seedlings representing 41 species of vascular plants emerged. Six (Rhexia virginica, Rhynchospora capitellata, Panicum spretum, Xyris difformis, Polygonum cureyi, Linum striatum) are rare in Ontario. Estimated seed banks for individual species were as high as 6,500 seeds m“2. If another low‐water phase occurs, a rich shoreline flora should again develop. We hypothesize that water‐level fluctuations are essential to the long‐term survival of these species.
STEREOLOGICAL METHODS FOR MEASURING INTERNAL LEAF STRUCTURE VARIABLES
Authors: Parkhurst David F.
Published: January 2018

A recent increase in research into ecological leaf anatomy is based partly on the effects of leaf structure upon photosynthesis. Hence, it is desirable to have efficient methods for measuring various aspects of internal leaf anatomy, such as percent air space and cell wall area per unit volume of tissue. Stereological methods make use of point counts and of counts of the number of intersections of sampling lines with tissue outlines on planar sections. Their practical use for measuring plant tissues is described, with special reference to highly directional tissue like palisade mesophyll and wood. In particular, the method for estimating cell wall area per unit volume requires the choice of a numerical factor which varies with tissue type. The factor has values of 2 for unoriented tissues, pI/2 for cylinders cut in cross section, and (p/2)2 for cylinders. in longitudinal section. An interpolating function to derive a value of the factor for tissues of intermediate type is also described. Leaves from two species of composites from contrasting habitats are compared, to demonstrate the usefulness of the methods.
OBSERVATIONS ON THE FINE STRUCTURE OF CALLIXYLON WOOD
Authors: Beck Charles B. , Coy Kathleen , Schmid Rudolf
Published: January 2018

Secondary wood of three species of Callixylon of Lower Mississippian age, preserved by three different modes (fusinization, silicification, and phosphatization), have been studied and characterized in detail. Problems of interpretation at the SEM level of permineralized woods, both containing (silicified wood of Callixylon erianum) and essentially lacking (phosphatized wood of C. arnoldii) original organic cell wall material, are analyzed and discussed. In particular, it is concluded that the flat to curved surfaces showing no evidence of apertures, observed in bordered pit pairs, commonly represent pit membrane surfaces. It is accepted, however, that some concave surfaces might be the mineral accretion surfaces of incomplete pit cavity casts as proposed by Leo and Barghoorn (1976). Regions between groups of pits, previously interpreted as crassulae, may be artifacts of preservation. The fusinized wood has the general appearance of charcoal, but unlike commercially produced charcoal provides evidence of its original microfibrillar structure. The origin of fusain in the fossil record is discussed, and it is concluded that it probably had several origins, including forest fire. Since charcoal can be produced naturally in the absence of O2 (Brown and Davis, 1973), the suggestion that fusain (charcoal) in the geologic column provides a basis for “assessing oxygen levels in paleoatmospheres” (Cope and Chaloner, 1980) is not supported. Natural sites of fusain production in the absence of O2 are regions of vulcanism and organic sediments inhabited by anaerobic microorganisms. A circular pattern of crystal orientation in the pit borders of C. arnoldii is interpreted to represent the original microfibrillar pattern. Pit apertures in C. arnoldii are shown to be circular to slightly elliptical. Interpretive evidence of heterogeneous pit membranes in C. arnoldii suggests but does not prove the presence of a torus. The distinctive central region in some pit membranes of the fusinized wood of Callixylon sp. might represent accumulations of waste metabolites. It is argued that a torus would be highly adaptive in large pits with circular apertures.
COMMUNITY STUDIES IN POLLINATION ECOLOGY IN THE HIGH TEMPERATE ANDES OF CENTRAL CHILE. I. POLLINATION MECHANISMS AND ALTITUDINAL VARIATION
Authors: Arroyo Mary T. Kalin , Primack Richard , Armesto Juan
Published: January 2018

Pollination mechanisms and pollinators are reported for a total of 137 species (75% of the non‐abiotically pollinated flora) as they occur at three altitudinal levels (subandean scrub: 2,200–2,600 m; cushion‐plant zone: 2,700–3,100 m; subnival feldfield: 3,200–3,600 m) in the Andean (alpine) zone on the Cordon del Cepo (33°17'S) in central Chile as part of community oriented research in reproductive biology in the high temperate Andes of South America. Only around 4% of the species studied failed to be visited by potential pollinators. Hymenopterans (principally bees) are important pollinators of 50% of the biotically pollinated flora, butterflies of 24% and flies of 46%. Other vectors include beetles, moths, and hummingbirds. An estimated 17% of the flora is anemophilous.

Bee species‐richness, specialist feeding, and melittophily reach maxima in the subandean scrub; thereafter, bees diminish rapidly in number, with bees pollinating only 13% of the subnival flora as contrasted with 68% of the subandean flora. Although fly and butterfly species‐richness also decline with increasing altitude, the proportions of species pollinated by these vectors actually increases. High‐altitude populations of melittophilous species with broad altitudinal ranges are invariably serviced by fewer bee species as compared with lower populations.

The rich bee fauna at the lower end of the Andean zone in central Chile appears to have resulted from upward colonization from that of the subtending lowland Mediterranean sclerophyllous woodland vegetation. Altitudinal variation in pollination spectra is discussed in relation to contrasting life history characteristics and different modes of thermoregulation in the insect groups involved.
OSMUNDA WEHRII, A NEW SPECIES BASED ON PETRIFIED RHIZOMES FROM THE MIOCENE OF WASHINGTON
Authors: Miller Charles N.
Published: January 2018

Silicified rhizomes from Miocene strata near Yakima, Washington represent a new species of Osmunda. The stems are 8–13 mm in diameter and are surrounded by a thick sheath of adherent leaf bases, each of which shows stipular expansions typical of the Osmundaceae. The new species has an ectophloic siphonostele in which the xylem cylinder is dissected by leaf gaps with 12–14 strands being visible in a given stem cross section. Such sections also show 12–16 leaf traces in the cortex. The xylem of each leaf trace diverges from the xylem cylinder of the stem as an adaxially concave strand with its protoxylem organized into a single medial adaxial cluster. Initial bifurcation of the leaf‐trace protexylem occurs as the leaf trace passes through the outer cortex of the stem. In the basal part of the stipular region of the petiole base, thick‐walled fibers form an arch on the abaxial side of the sclerenchyma ring around the petiolar bundle. This arch persists throughout most of the length of the stipular region, with the thick‐walled fibers becoming reorganized into two lateral masses in the distal part of the stipular region. Similar thick‐walled fibers form an elongate strip of tissue in each wing of the stipule along with several small clusters scattered near the sclerenchyma ring. The new species belongs to the subgenus Osmunda and shows that during the Neogene, the latter existed as a group of closely related species much as it does today. Furthermore, Osmunda wehrii combines features of the modern O. regalis, O. japonica, and O. lancea with those of O. claytoniana and thus supports the inclusion of the latter species in the subgenus Osmunda.
FLORAL BIOLOGY, HUMMINGBIRD POLLINATION AND FRUIT PRODUCTION OF TRUMPET CREEPER (CAMPSIS RADICANS, BIGNONIACEAE)
Authors: Bertin Robert I.
Published: January 2018

Trumpet creeper is self‐incompatible and bears long, tubular, orange flowers from June to September. Flowering peaks rapidly, then declines and continues at low levels for several weeks. The initial burst of flowering may attract pollinators that return even during subsequent reduced flowering. Most flowers open before noon and nectar production totals 110 μl of 26% sucrose equivalents per flower, an exceptionally high production for a temperate zone plant. Production ceases within 20–30 hr of flower opening, but corollas persist for several days and may serve to attract pollinators. Effective pollination reduces the period of stigma receptivity and speeds closing of stigma lobes. Only 1–9% of flowers produced mature fruits at four sites in Illinois and Missouri. Roughly 400 pollen grains had to be deposited on a receptive stigma to cause fruit development beyond an initial period of high abortion. At two sites, 17% and 89% of stigmas received over 400 pollen grains. Assuming 50% of deposited grains were from the same plant, fruit production at one site was clearly pollinator limited, that at the second site may have been. Ruby‐throated Hummingbirds (Archilochus colubris) deposited ten times as much pollen per stigma per visit as honeybees (Apis mellifera) and bumblebees (Bombus spp.). Fruit set was highest where rubythroat visitation was most frequent. Trumpet creeper appears primarily adapted for hummingbird pollination, but can also be adequately pollinated by honeybees and bumblebees. This is one of the first attempts to relate pollen‐depositing capabilities of pollinators of any plant to pollen requirements for fruit production. Several characteristics suggest that trumpet creeper may be adapted to pollination at low densities (often called traplining) in its presumed original, woodland, habitat.
FINE STRUCTURE OF MISTLETOE POLLEN. V. MADAGASCAN AND CONTINENTAL AFRICAN VISCUM L. (VISCACEAE)
Authors: Feuer Sylvia M. , Kuijt Job , Wiens Delbert
Published: January 2018

Pollen characters of Madagascan and continental African Viscum are described and compared to those in Asia and Australia. The subprolate, tricolporate, nonuniformly sculptured pollen of Madagascan taxa is most similar to that of Asian species. Ultrastructurally, however, the completely granular equatorial ektexine of Madagascan Viscum is most similar to that of continental African taxa. Continental African Viscum, in contrast to Madagascan and Asian species, display a wide variation in pollen shape and apertures. Pollen shape ranges from subprolate to oblate, the latter unique to Africa. The most striking feature of continental Viscum is their variability in aperture number and aperture type. Aperture number varies at both the intra‐ and interpopulational levels with such variation resolvable to the individual flower—a condition unique to the continent. The only simple (colpate) aperture type in the genus is restricted to Africa. The continental species can be divided into two species groups based on pollen characters: Group I (4 spp.) characterized by strictly tricolporate rounded convex pollen with a rodlet/granular equatorial ektexine structure and Group II (most continental species) possessing multiapertures, concave lobate shape, uniform sculpturing and granular equatorial ektexine. The African V. menyharthii, V. fischeri, V. rotundifolium and V. minimum exhibit no clear Group I or II affinities. An analysis of overall pollen characters in Viscum indicates a trend towards spheroidal shape, multiapertures and uniform sculpturing and ektexine organization. Though pollen characters suggest ties between Australia, Asia and Madagascar, they indicate an even stronger relationship between Madagascar and continental Africa, particularly eastern Africa. The relationship of the majority of African Viscum, excluding those with obvious Madagascan affinities, remains obscure. The unique palynological features of Group II species coupled with their inflorescence structure suggest an independently evolving group.
CONTROL OF VEGETATION ON CONTRASTING SUBSTRATES: HERB PATTERNS ON SERPENTINE AND SANDSTONE
Authors: Moral Roger del
Published: January 2018

Binary discriminant analysis (BDA) reveals relationships between species distributions and environmental variables. In this study, BDA was applied to transects on serpentine and sandstone in the Wenatchee Mountains, Washington. Species presence and states of ten habitat variables were recorded in each quadrat. Species response patterns significantly different from a random expectation suggested that distributions are controlled by soil moisture far more strongly on serpentine than they are on sandstone, where light and its correlates are more important. Environmental patterns were explored with direct principal components analysis (PCA) of standardized environmental variables and indirectly by PCA of the significant D‐values. The latter is biased towards variables to which species respond strongly. The results emphasize the environmental and floristic contrasts between substrates. On serpentine, direct PCA indicates that effective moisture, soil fertility, and insolation control the first three axes, while on sandstone, insolation, fertility, and effective moisture control the first three axes, respectively. The PCA of D‐values (Q‐mode) is similarly interpreted: moisture is strongly correlated with the first component on the serpentine transect, while insolation and fertility are correlated with the first component on sandstone. Species ordinations also result from Q‐mode analysis. They reflect species responses to the identified gradients and indicate mutual species‐environment interactions. These analyses conform to the hypothesis that mineral conditions of serpentine select against intolerant species and that survivors respond primarily to moisture conditions that are a result of low productivity, attributable to adverse nutrient conditions. On sandstone, the moisture gradient is less pronounced, and direct canopy effects that create variable light conditions predominate. BDA is a useful tool in ecological survey and pattern analysis. Species responses to environmental factors may be estimated quickly and directly. This method will help to focus subsequent research, improve experimental design, and generate explicit and testable hypotheses about species‐habitat interactions.
CORDAIANTHUS DUQUESNENSIS SP. NOV., ANATOMICALLY PRESERVED OVULATE CONES FROM THE UPPER PENNSYLVANIAN OF OHIO
Authors: Rothwell Gar W.
Published: January 2018

Four anatomically preserved cordaitean cones have been discovered in Upper Pennsylvanian sediments of Ohio, and these provide evidence for the description of Cordaianthus duquesnensis sp. nov. Specimens consist of isolated shoots. Each exhibits sterile scales, ovule‐bearing scales and scales from which ovules have apparently abscised. Cones are up to 5.5 mm long and 2.2 mm in maximum diameter, with fertile scales restricted to the distal region. Ovules occur singly at the tip of fertile scales and all are either immature or abortive. A comparison of scales and ovules at the apex with those in progressively more proximal regions forms the basis for interpreting several features of cone and ovule ontogeny.