bluuebunny/crossref_metadata_2025 huggingface dataset:
GENERIC REDEFINITION IN SUBTRIBE SPIRANTHINAE (ORCHIDACEAE)
Authors: Balogh Pamela
Published: January 2018

The orchid family is divided into five subfamilies and further divided into 21 tribes and 63 subtribes (Dressler, 1981). Subtribe Spiranthinae (tribe Cranchideae, subfamily Spiranthoideae) is treated here as consisting of approximately 250‐300 species in 16 genera. These genera are Brachystele, Buchtienia, Cutsis, Cyclopogon, Deiregyne, Discyphus, Eurystyles, Hapalorchis, Odontorrhynchos, Pelexia, Pseudogoodyera, Sarcoglottis, Sauroglossum, Schiedeella, Spiranthes, and Stenorrhynchos. Eleven of these genera may be grouped into four generic alliances using the rostellum/viscidium attachment as the basis for these alliances. The Brachystele alliance includes Brachystele, Sauroglossum, and Odontorrhynchos and has a very reduced rostellum which is usually inseparable from the viscidium. The Pelexia alliance includes Cyclopogon, Pelexia, and Sarcoglottis and has an elongate, broad, laminar rostellum which is partially adherent to the viscidium. The Spiranthes alliance includes Discyphus, Hapalorchis, and Spiranthes and has a broad, laminar rostellum which is centrally adherent to the viscidium. The Stenorrhynchos alliance includes Schiedeella and Stenorrhynchos and has a subulate rostellum which is ensheathed by the viscidium. Previous studies (Schlechter, 1920) of this subtribe were based on characteristics of the rostellum and perianth. Pollinarium morphology is reported for the first time.
A TECHNIQUE FOR COUNTING CHROMOSOMES OF ARMORED DINOFLAGELLATES, AND CHROMOSOME NUMBERS OF SIX FRESHWATER DINOFLAGELLATE SPECIES
Authors: Holt Jack R. , Pfiester Lois A.
Published: January 2018

A technique is presented to stain, squash, and enumerate thecate dinoflagellate chromosomes using a cellulose incubation and propionocarmine stain. Chromosome numbers for six freshwater armored dinoflagellates (Peridinium cinctum (O.F.M.) Ehrenberg, P. inconspicuum Lemm., P. limbatum (Stokes) Lemm., P. volzii Lemm., P. willei Huit.‐Kaas, and Peridiniopsis polonicum (Wolosz.) Bourrelly) range from 41 (P. inconspicuum) to 210 (P. cinctum). Evidence is presented for dinoflagellate aneuploidy in culture.
ALLELOPATHIC GROWTH INHIBITION OF NODULATED AND UNNODULATED ALNUS CRISPA SEEDLINGS BY POPULUS BALSAMIFERA
Authors: Jobidon Robert , Thibault J.‐R.
Published: January 2018

Water extracts of fresh leaves, buds, and leaf litter of Populus balsamifera (balsam poplar) were tested at different dilutions for allelopathic effects on nodulation, nitrogenase activity and growth of nodulated green alder (Alnus crispa) seedlings, and on growth of unnodulated green alder seedlings. All extracts inhibited height growth, root elongation and dry weight increment of nodulated and unnodulated green alder seedlings to some degree during a 2‐month experiment. Foliar nitrogen content of both nodulated and unnodulated seedlings was significantly lower in extract treated plants than in controls. Growth inhibition was about 25% less in nodulated than in unnodulated seedlings. The number of nodules per plant in seedlings treated with any balsam poplar extract was only 51% that of control plants. Acetylene reduction by seedlings treated with bud and leaf litter extracts indicated a decrease of 62% compared to controls. Growth inhibition was not mediated by pH or osmotic effects of the extracts. The possible ecological significance is discussed.
FRUIT TRAITS, AND SEED CONSUMPTION BY RODENTS, OF CRESCENTIA ALATA (BIGNONIACEAE) IN SANTA ROSA NATIONAL PARK, COSTA RICA
Authors: Janzen D. H.
Published: January 2018

The pulp in the large hard fruits of Crescentia alata (Bignoniaceae: jicaro) are eaten by horses, surrogate Pleistocene dispersal agents, and the seeds pass through the horse to germinate in dung. I hypothesize that the distribution of jicaro has probably changed dramatically with the introduction of the horse. Two samples of ripe jicaro fruits weighed an average of 210 and 390 g, and contained an average of about 400 and 600 seeds. There was strong variation within and between two trees in the number of seeds per fruit. Mature live seeds weighed an average of 36 and 40 mg, but varied strongly in weight between and within fruits. The seeds were found to be highly edible to a small terrestrial native rodent (Liomys salvini, Heteromyidae) and this rodent avidly harvests the seeds from horse dung but cannot open the hard fruits by itself. The interaction between horses, jicaro fruits, and Liomys mice is probably representative of that which used to occur between Pleistocene megafauna and a number of contemporary Central American trees.
AUTOGAMY AND COMPETITION FOR POLLINATORS IN HEPATICA AMERICANA (RANUNCULACEAE)
Authors: Motten Alexander F.
Published: January 2018

Hepatica americana is one of the earliest flowering vernal herbs in the deciduous forests of piedmont North Carolina. Unlike most other members of the spring wildflower community, its flowers are nectarless and autogamous. The number of insect visits a flower receives varies markedly through the blooming season and is lowest when H. americana is in full bloom. Potential for outcrossing as measured by the seed set of emasculated flowers follows the same pattern. The mid‐season decline in insect‐pollination is most likely the result of competition with Erythronium umbilicatum, which flowers concurrently with H. americana and is much more attractive to the solitary bees that are the principal early season pollen vectors. Because of this competitive disadvantage, seed set of H. americana in piedmont North Carolina would be pollination‐limited if the flowers were not autogamous. Autogamy may also be favored by flowering early in the spring before pollinators are available. Opportunities for outcrossing in H. americana are primarily the result of protogyny and blooming earlier than competitors.
PEARL MILLET (PENNISETUM AMERICANUM (L.) LEEKE) AND GRAIN SORGHUM (SORGHUM BICOLOR (L.) MOENCH) ULTRASTRUCTURE
Authors: Zeleznak Kathleen , Varriano‐Marston E.
Published: January 2018

Ultrastructural features of pearl millet (Pennisetum americanum (L.) Leeke) and grain sorghum (Sorghum bicolor (L.) Moench) caryospses were investigated with thin sections of the dry, mature grain in the transmission electron microscope, and fractured kernels in the scanning electron microscope. The pericarp of those grains is comprised of three distinct layers: epicarp, mesocarp of parenchyma cells, and endocarp of compressed cross and tube cells. Mesocarp cells of grain sorghum contain starch granules embedded in a cytoplasmic matrix. The major constituent of sorghum and millet aleurone cells are aleurone grains (protein bodies) and lipid bodies. Subaleurone cells contain a much higher proportion of protein bodies than starch granules, and the protein bodies are structurally distinct from those in the aleurone. The germ scutellar ultrastructures of the two grains were similar; protein bodies, lipid bodies, epidermal cells and parenchyma cells of the germ are described.
LITTER NUTRIENT CONTENT AND PRODUCTION IN THE GREAT DISMAL SWAMP
Authors: Gomez Marta M. , Day Frank P.
Published: January 2018

Litter production was studied in the Great Dismal Swamp, Virginia in four plant communities which differ primarily in species composition and flooding regime. Greatest leaf deposition occured in the more flooded communities, maple‐gum (Acer‐Nyssa) with 536 gm‐2 yr‐1 and cypress (Taxodium distichum (L.) Richard) with 528 gm‐2 yr‐1, followed by the cedar (Chamaecyparis thyoides (L.) BSP) and mixed hardwood (Quercus‐Acer‐Nyssa‐Liquidambar) communities, with 506 gm‐2 yr‐1 and 455 gm‐2 yr‐1, respectively. Apparently periodic flooding promotes production. Peaks occurring in October and November corresponded to autumn leaf fall, while peaks in January and May were due to some leaf litter combined with a large amount of woody litter. Litter nutrient concentrations were higher, except for Ca, in the most abundant species (cypress and water gum) in the frequently flooded cypress community. Higher leaf fall rates and litter nutrient concentrations resulted in greater nutrient deposition in the cypress and maple‐gum communities.
WOMEN IN NINETEENTH CENTURY AMERICAN BOTANY; A GENERALLY UNRECOGNIZED CONSTITUENCY
Authors: Rudolph Emanuel D.
Published: January 2018

Botany was thought to be a suitable study for young women in schools and an amateur avocation in the Nineteenth Century. A surprisingly large number of American women identified themselves as being seriously interested in botany. For example, in the first published directory of American botanists in 1873, 13 percent of the 599 names are women's and that increased to 16 percent of the 982 names in 1878. In this paper, 1,185 women have been identified as a sample of those actively interested in botany during the century. Less than 2% of them were active before 1870, and most of them, 67%, resided in New England and the Middle Atlantic States. Almost three quarters of them were unmarried, and only 10% had higher educational degrees although 15% had some identifiable profession. Some particular individuals are noted for their contributions to science, their activity as plant collectors, and their support of botanical societies. Though few American women became professional botanists in the Nineteenth Century, they constitute an important overlooked constituency for the developing profession of botany.
VESTIGIAL STRUCTURES AND THE FLOWER
Authors: Wilson Carl L.
Published: January 2018

Overemphasis upon well‐established correlations between floral morphology and pollination agents and mechanisms may lead to a neglect of certain aspects of the vascular anatomy of the flower. Thus statements have been made that the anatomy of flowers can be studied meaningfully only in relation to particular modes of pollination, dispersal, and allied functions; that all vascular bundles in the flower are physiologically useful; and that no vestigial bundles offer clues to past evolutionary events. Such statements are here controverted by calling attention to examples of vestigial and presumably functionless vascular bundles in the flower. These are of two general kinds: 1) Vascular “stubs,” bundles that persist after the structures they formerly supplied have disappeared. Although the existence of such stubs has been questioned or denied, they do exist. Their number (except for the relatively common strands leading to lost ovules) has been exaggerated, however, and they are not usually found where they might be expected. 2) Longer vascular bundles associated with, or a part of, highly reduced floral organs. Examples of both of the above categories are provided.
GROWTH PATTERNS OF PLANTS THAT MAXIMIZE VERTICAL GROWTH AND MINIMIZE INTERNAL STRESSES
Authors: Niklas Karl J. , O'Rourke Thomas D.
Published: January 2018

The geometry of plant axis flexure is analyzed as the result of orthotropic growth and the stresses caused by a vertical weight distribution along the axis. Distal responses to light and gravity and proximal sagging flexure result in a curvilinear axial geometry. The stresses associated with this geometry are analyzed by means of the flexure theory for curved beams. A flexed plant axis is shown to conform to some portion of a logarithmic spiral, r = r0ekθ, of which a special case is circular flexure, k 0. Calculations of the maximum bending moment, Mmax and the maximum tensile stress, max, acting parallel to the axis indicate that the optimal mode of flexure (one that minimizes Mmax and max) is some arc of a circle. Examination of 11 plant taxa indicates that this mode of curvature is statistically the most prevalent condition in plants lacking or having limited secondary growth. Indeterminate apical growth of orthotropic axes is shown to result in a type of failure where portions of vertical axes are reapportioned into a horizontal or supported position.
MORPHOLOGICAL STUDIES OF THE NYMPHAEACEAE. XII. THE FLORAL BIOLOGY OF CABOMBA CAROLINIANA
Authors: Schneider Edward L. , Jeter John M.
Published: January 2018

Observations have been made on the pollination ecology of Cabomba caroliniana Gray in Texas. Flowers are trimerous with morphologically similar perianth parts. The adaxial corolla spurs are nectariferous and attract small Diptera (e.g. Notiphila cressoni and Hydrellia bilobifera). Anthesis occurs for 2 consecutive days with flowers opening about 10:00 a.m. and closing around 4 p.m. on each day. First‐day flowers have short, indehiscent stamens and longer pollen‐receptive stigmata which arch outward over the nectaries. In 2nd‐day flowers the stamens have elongated to the level of the stigmata and extrorse dehiscense occurs above the nectaries. Stigmata of 2nd‐day flowers are pressed together at the center of the flower and are nonreceptive to pollen. Insects attracted to 2nd‐day flowers in search of nectar become dusted with pollen (due to the position and extrorse dehiscence of the anthers) and as insects fly to 1st‐day flowers, achieve cross‐pollination by virtue of the stigmata position over the nectaries. Seed anatomy is similar to that of other nymphaeaceous genera (i.e., abundant perisperm, little cellular endosperm, a haustorial nucellar “tube,” and a small dicotyledonous embryo). Pollination morphology and comparative xylem anatomy support the segregation of Cabomba from the Nymphaeaceae, sensu stricto. The anatomical correlations between seeds and the myophilous pollination syndrome (found elsewhere in Nymphaeaceae, sensu lato), however, suggest a phyletic relationship.
ANATOMICAL AND PHYSIOLOGICAL STUDIES OF FLORAL TUBE ELONGATION OF CROCUS VERNUS (IRIDACEAE)
Authors: Stark Dixie Sue Patten
Published: January 2018

Intact floral tubes of Crocus vernus grown under controlled conditions elongated 50 mm in 8 days. Mitoses of the epidermal cells did not occur during the growth of the intact tube; however, cells did elongate from 50 μm to 150 μm, a three‐fold increase in cell length. When the floral buds were excised and maintained in distilled water, elongation of floral tubes was inhibited by 46%. The presence of the ovary or the addition of nutrients had no significant effect upon the elongation of the floral tubes of excised buds. When the excised floral buds were placed in 10–6 m indoleacetic acid, the final tube lengths exceeded that of the water controls by 30% and achieved 91% of the elongation of the intact tubes. Gibberellic acid and kinetin had no effect on floral tube elongation. As with the intact floral tubes, mitoses of the epidermal cells did not occur during the elongation of the excised floral tubes.
A MORPHOMETRIC STUDY OF THE ULTRASTRUCTURE OF ECHINOCEREUS ENGELMANNII (CACTACEAE). VII. HOMOGENEITY OF ZONES IN THE SHOOT APICAL MERISTEM
Authors: Mauseth James D.
Published: January 2018

Median longitudinal sections of shoot apical meristems of Echinocereus engelmannii were photographed such that the location of each cell was mapped. The maps of the peripheral zone and the pith‐rib meristem were divided into upper, middle, and lower thirds, and then the upper and lower regions were analysed stereologically. Statistical comparisons of the upper regions vs. the lower regions within each zone indicate that there are no significant differences between them. The cells do not change detectably as they “flow” from the top of the meristem to the bottom.
CLEISTOGAMY IN ANDROPOGON L. (GRAMINEAE)
Authors: Campbell Christopher S.
Published: January 2018

Eleven species of Andropogon produce single‐stamened flowers, and all but one of these species bear some cleistogamous flowers. Nine of the species, all diploid perennials, make up the Andropogon virginicus complex. Cleistogamy in the virginicus complex results from precocious maturation of the flowers, which leaves them confined within their spikelets at anthesis. Variation in flowering mode (expressed as mean % chasmogamy) is correlated significantly (P < 0.01) with variation in peduncle length (rs = 0.67), spikelet length (rs = 0.49), and anther length (rs = 0.69). The strength of the correlation (r = 0.94) between pollen grain number per anther and anther length makes the latter a good measure of pollen‐ovule ratios in the single‐stamened flowers of this group. Taxa with the highest frequency of cleistogamous flowering are also the most successful colonizers of disturbed habitats. It is suggested that cleistogamy is important in the reproductive isolation of the numerous, closely related subspecific taxa of the virginicus complex.
BREEDING SYSTEM AND POLLINATION ECOLOGY OF TRIENTALIS BOREALIS (PRIMULACEAE)
Authors: Anderson Roger C. , Beare Michael H.
Published: January 2018

Selfing in Trientalis borealis is reduced by spatial separation of stigma and anthers during anther dehiscence and by internal self‐incompatibility. Artificial self‐pollination resulted in low levels of fruit set (2.0%). Crosses made within patches of plants yielded variable (0–72.7%), but generally low fruit set (x̄ = 21.4%). This may be caused by patches often consisting of a single genet. In contrast crosses made among patches resulted in uniformly high levels of fruit set (x̄ = 84.3%). Pollinator activity was higher at open sites than at heavily shaded sites and was correlated with fruit set. Pollinator activity, however, showed no correlation with seed set. We conclude that the primary pollinators, Halictid and Andrenid bees, play an important role in the breeding system of the plant by promoting outcrossing but that availability or efficiency of pollinators may limit seed set.
FERTILIZATION IN PLUMBAGO ZEYLANICA: GAMETIC FUSION AND FATE OF THE MALE CYTOPLASM
Authors: Russell Scott D.
Published: January 2018

Developmental phases surrounding the processes of gametic delivery and fusion were examined ultrastructurally in the reduced megagametophyte of Plumbago zeylanica, which lacks synergids. Gametic delivery occurs at the end of pollen tube growth and results in deposition of two male gametes, a vegetative nucleus, and a limited amount of pollen cytoplasm between the egg and central cell. Discharge of these materials from the tube is accompanied by loss of inner and outer pollen tube plasma membranes, loss of sperm‐associated cell wall components, and disruption of the formerly continuous cell wall between the egg and central cell. The dispersion of egg cell wall components directly exposes female reproductive cell membranes to the unfused male gametes and pollen tube without disrupting gametic cell plasma membranes. Presence of unfused sperms within the female gametophyte appears to be a transitory phenomenon, lasting less than 5 min at the end of over 8½ hr of pollen tube growth. At the time of gametic deposition, plasma membranes of unfused sperm cells become directly appressed to plasma membranes of both the egg and central cell. Gametic fusion is initiated by a single fusion event between membranes of participating male and female cells, which is rapidly followed by subsequent, secondary fusion events between the same two cells at different locations along their surface. Gametic fusion results in the transmission of male gamete nuclei with co‐transmission of nearly the entire sperm cytoplasmic volume and organellar complement, and it is possible to identify heritable male cytoplasmic organelles within both the incipient zygote and endosperm. Paternally originating plastids may be distinguished from maternal plastids by differences in morphology and staining characteristics, whereas paternal mitochondria may be distinguished from maternal mitochondria by populational differences in mitochondrial size which are statistically significant. Such observations further indicate that transmitted paternal mitochondria seem to remain viable, as judged by their ultrastructural appearance, and are transmitted exclusively by sperm cytoplasm rather than discharged pollen cytoplasm. The presence of anucleate, membrane‐bounded cytoplasmic bodies between the egg and central cell are identifiable on the basis of their enclosed organelles and indicate that fragmentation of a small amount of the sperm cytoplasm associated with the vegetative nucleus commonly occurs. The presence and identification of sperm cytoplasmic organelles and associated membranes within female reproductive cells following gametic transmission represents strong evidence in support of the cellular basis of nuclear and cytoplasmic transmission during sexual reproduction in Plumbago.
ORGAN INITIATION AND THE DEVELOPMENT OF UNISEXUAL FLOWERS IN THE TASSEL AND EAR OF ZEA MAYS
Authors: Cheng P. C. , Greyson R. I. , Walden D. B.
Published: January 2018

The development of the unisexual male and female flowers of Zea mays from bisexual initials in both tassels and ears has been reinvestigated with SEM and TEM. The early stages of spikelet branch primordia, spikelet initiation, and early flower development are similar in both flowers, though differences in rates of growth of glumes, lemmas, and palea were detected. In both tassel and ear flowers, a pair of stamens arises opposite the lemmas and a third stamen initiates later at right angles to the first pair but from a point on the meristem below its insertion. Gynoecia develop on both tassel and ear flowers first as a ridge which overgrows the apical meristem giving rise to the stylar canal and the elongate silk. Male flowers arise in the tassel through selective vacuolation and abortion of the cells of the early gynoecium. The single female flower in each ear spikelet arises through the vacuolation and abortion of stamens in the upper flower and the repression of growth of and the eventual regression of the lower flower in each spikelet. The significance of these selective organ abortions for practical applications is discussed.
SEXUAL DEVELOPMENT OF ONOCLEA SENSIBILIS ON AGAR AND SOIL MEDIA WITHOUT THE ADDITION OF ANTHERIDIOGEN
Authors: Rubin G. , Paolillo D. J.
Published: January 2018

Onoclea sensibilis gametophytes grown on agar, unsterilized soil or ashed soil without the addition of antheridiogen developed antheridia after the notch meristem was formed. There was a linear increase in maleness through time on all three media. Antheridial production on agar was delayed nearly 3 wk. Agar had a significantly higher proportion of females than ashed soil or unsterilized soil. It was concluded that agar is an inappropriate medium for experiments on the mechanism of sexual development in Onoclea gametophytes.
GROWTH OF EXCISED PEA EMBRYONIC AXES ON DIFFERENT SUGARS
Authors: Davis Bill D.
Published: January 2018

Excised pea embryonic axes were cultured on mineral salts plus various carbon sources. Growth continued for at least 3 wk, as measured by increased length, fresh and dry wt, sugar content, and β‐amylase activity. The optimum sucrose concentration for elongation and fresh wt accumulation was 5% (w/v), although dry wt and sugar content increased in cultures containing 10 to 20%. Comparable growth was observed for axes cultured on 2% sucrose, glucose, fructose, or maltose.
VARIATION IN THE DEGREE OF CLEISTOGAMY WITHIN AND AMONG SPECIES OF THE GRASS DANTHONIA
Authors: Clay Keith
Published: January 2018

North American species of the grass Danthonia bear distinct chasmogamous and cleistogamous flowers. Four taxa occurring in North Carolina (D. compressa, D. epilis, D. sericea, and D. spicata) were examined for variation in the degree of cleistogamy. The flowering culms bear a single terminal panicle consisting of 4 to 12 spikelets of chasmogamous flowers. In each leaf axil, at the nodes of the flowering culm, is a single spikelet of cleistogamous flowers completely surrounded by the leaf sheath. The percentage of cleistogamous flowers produced on any culm depends on the number of chasmogamous and cleistogamous spikelets and the number of flowers in each type of spikelet. All four characters vary among the taxa examined. Danthonia compressa produces, on the average, 50% cleistogamous flowers; D. spicata, 25% cleistogamous flowers; D. sericea and D. epilis, 5% cleistogamous flowers. The degree of cleistogamy in D. spicata is associated with certain habitat features. Populations from mountain sites, disturbed sites, and non‐woodland sites produced higher percentages of cleistogamous flowers than did populations from piedmont, undisturbed, and woodland sites, respectively. Grazing may favor increased cleistogamy because cleistogamous flowers are produced lower on the plant. In North Carolina, the most frequently grazed Danthonia taxa also produce the highest percentage of cleistogamous flowers.
DIURNAL ACID METABOLISM IN ISOETES HOWELLII FROM A TEMPORARY POOL AND A PERMANENT LAKE
Authors: Keeley Jon E. , Mathews R. Patrick , Walker Cindy Miller
Published: January 2018

Water chemistry and titratable acidity and malic acid levels in Isoetes howellii leaves were sampled every 6 hr from plants in a seasonal pool and an oligotrophic lake. Plants in the seasonal pool showed a diurnal fluctuation of ~ 300 μequivalents titratable acidity g−1 fresh wt; daytime deacidification was 75% complete by noon and nighttime acidification was 45% complete by midnight. Late in the season after the pool had dried, emergent leaves showed only a very weak tendency to accumulate acid at night. Plants from the oligotrophic lake had a diurnal change of ~100 μeq g−1 fresh wt, daytime deacidification was only 45% complete by noon but nighttime acidification was 80% complete by midnight. Water characteristics were distinctly different between these two systems. In the seasonal pool there were marked diurnal changes in temperature, pH, oxygen and carbon dioxide. Free‐CO2 levels were an order of magnitude greater in the early morning than in the late afternoon. In contrast, the conditions in the oligotrophic lake showed no marked diurnal fluctuation, though total inorganic carbon levels were extremely low relative to other aquatic systems.
NOTE ON THE CHEMICAL NATURE OF THE ADHESIVE OF VISCID DISCS IN CATASETUM FIMBRIATUM LINDL. (ORCHIDACEAE)
Authors: Schlee D. , Ebel F.
Published: January 2018

Viscid disc adhesive of pollinaria of the orchid, Catasetum, was analyzed for sugars and amino acids by TLC. Sucrose, glucose, and fructose are predominant; two other unidentified aldoses are present. Glucosamine, or one of its derivatives, apparently also is present. Glycine and serine predominate in the protein hydrolysate, and glutamate and aspartate are in high content. The adhesive appears to be a glycoprotein.
SYSTEMATIC SIGNIFICANCE OF SEED‐SURFACE FEATURES IN ORTHOCARPUS (SCROPHULARIACEAE—SUBTRIBE CASTILLEJINAE)
Authors: Chuang T. I. , Heckard L. R.
Published: January 2018

Scanning electron microscope and light microscope examination of seed‐coat features of 26 species of Orthocarpus have allowed recognition of many species‐level differences (summarized in a key) and of three seed‐coat types that parallel taxonomic subgroups but support realignments at generic and infrageneric levels. Type 1 seeds (subg. Orthocarpus, sect. Orthocarpus) have a lateral hilum, sculptured inner tangential seed‐coat walls, and a tightly fitting outer seed coat. They are very similar to seeds of Cordylanthus. Seeds of Types 2 and 3 have a terminal hilum and membranous inner tangential cell walls. Type 2 seeds (subg. Orthocarpus, sects. Castillejoides and Cordylanthoides, with one exception) have a net‐like, loosely fitting outer seed coat that shows close relationship to seeds of Castilleja. Inner tangential walls of Type 2 seeds normally rupture. Type 3 seeds (subg. Triphysaria, with two exceptions) have a tightly fitting outer seed coat and inner tangential walls are always retained. Seed features support evidence from floral morphology and chromosome numbers that Orthocarpus as currently recognized is not a monophyletic lineage.
THE SEASONAL CYCLE OF PHLOEM DEVELOPMENT IN JUNIPERUS CALIFORNICA
Authors: Alfieri Frank J. , Kemp Romelle I.
Published: January 2018

In Juniperus californica, all sieve cells of the previous season's phloem growth increment overwinter in a mature state. Initiation of cambial activity begins in early March and, by the end of March, the oldest sieve cells that overwintered lose their contents and die. By mid‐April, even the youngest sieve cells of the previous season's growth increment have lost their contents. The period of greatest cambial activity begins in the last half of April and continues through May. With the slowing of cambial activity in June, callose begins to collect on the sieve areas of the first‐formed sieve cells of the new increment. By July, the cambium and phloem are in a dormant state. Initiation of phloem production precedes that of the xylem by about 1 month. Production of new xylem and phloem ceases simultaneously in July.
COMPARATIVE REPRODUCTIVE BIOLOGY OF ACER PENSYLVANICUM AND A. SPICATUM (ACERACEAE)
Authors: Sullivan Janet R.
Published: January 2018

Pollination mechanisms and floral features affecting reproduction were examined in two closely‐related species, Acer pensylvanicum and A. spicatum. Intra‐specific crossing experiments, studies of pollen stainability and ovule number, and observations of the flowers in the field revealed that neither species bears functionally hermaphroditic flowers. Three flower‐types were found in each species: staminate, pistillate, and a third type that is morphologically hermaphroditic. The latter form sheds viable pollen, but the pistil does not contain ovules. Pollen‐ovule ratios of both species are in the range of expectation for a facultatively xenogamous reproductive system. Outcrossing is accomplished by entomophily in both species. A variety of insects from several orders visit the flowers; however bees in the genus Andrena (Hymenoptera: Andrenidae), especially A. milwaukeensis, are considered the most important pollinators of both maple species because of their fidelity to Acer, their intrafloral behavior, and their ability to carry pollen. However, flies are the most abundant visitors to A. pensylvanicum. Apomixis is an important means of reproduction in A. spicatum. Although floral phenology of these maple species overlaps within a geographical region they were never found blooming simultaneously when growing together.
RE‐EVALUATION OF CERTAIN KEY RELATIONSHIPS IN THE ALISMATIDAE: FLORAL ORGANOGENESIS OF SCHEUCHZERIA PALUSTRIS (SCHEUCHZERIACEAE)
Authors: Posluszny Usher
Published: January 2018

Transition to flowering in the North‐temperate bog plant Scheuchzeria palustris occurs in early May and results in the formation of a simple raceme with six flowers. Five of the flowers are subtended by large foliar bracts, while the sixth and last‐formed flower on the inflorescence remains ebracteate. The individual flowers develop along a clearly trimerous pattern. The three outer tepals develop first, arising almost simultaneously at the periphery of the triangular floral apex. They are followed closely by the development of the three anti‐tepalous outer stamens. The three inner tepals are next in the developmental sequence, alternating with the outer whorl of tepal‐stamen pairs but arising at a slightly higher level on the floral meristem. Three inner stamens are initiated opposite the inner tepal primordia. Finally, three gynoecial primordia are initiated on the remaining central portion of the floral apex and alternating with the inner whorl of tepal‐stamen pairs. Each carpel develops at first as a horseshoe‐shaped structure. Two ovules form in each carpel, initiating on the adaxial margin of the carpel wall. Histogenesis of all floral appendages involves initially periclinal divisions in the second tunica layer followed by corresponding anticlinal divisions in the first tunica layer and concurrent activity in the underlying corpus. Separate procambial strands differentiate acropetally from the inflorescence axis to each tepal‐stamen pair and then bifurcate. The vascular connection to the gynoecium develops directly from the strands in the tepal‐stamen pairs. The results of this developmental study of the flower of S. palustris have a significant bearing on the positioning of this and related taxa within the Alismatidae and on the speculation of the phylogeny of the monocotyledon flower.
RELATIONSHIP AMONG VESSEL DIAMETER, VESSEL FREQUENCY, AND SPACING OF PARENCHYMA BANDS IN WOOD OF CARYA TOMENTOSA NUTT., MOCKERNUT HICKORY
Authors: Hill Jane F.
Published: January 2018

Vessel‐lumen diameter, vessel frequency, and spacing of concentric, tangential bands of parenchyma cells follow well defined trends across annual growth rings of Carya tomentosa Nutt., mockernut hickory. These cross‐ring cellular changes were correlated with each other to a considerable degree but not tightly linked. Vessel‐lumen diameter decreased in a strongly linear fashion, as a function of distance from the inner ring boundary. Distance between tangential, concentric bands of axial wood parenchyma cells also decreased across rings, but followed a less strongly linear trend. Vessel frequency decreased abruptly after the large‐pore zone and then increased to the outer ring boundary. Radial growth rate, as indicated by ring width, strongly influenced these trends. For all three cellular characteristics, the cross‐ring trend was abrupt in narrow rings and more gradual in wide rings. An anomalous ring of Carya tomentosa, and three similar rings of Carya glabra (Mill.) Sweet, showed a decrease in interband distance and then an abrupt increase followed by another decrease to the outer ring boundary, whereas vessel diameter remained small and uniform after an initial decrease. The three cellular characteristics were concluded to be under separate physiological controls, although growth rate seems to exert a considerable, parallel influence on them.
PLASTID DEVELOPMENT IN IOJAP‐ AND CHLOROPLAST MUTATOR‐AFFECTED MAIZE PLANTS
Authors: Thompson Deborah , Walbot Virginia , Coe E. H.
Published: January 2018

Plastids affected by either iojap or chloroplast mutator fail to green, and altered plastids are maternally transmitted to subsequent generations. The ultrastructure of iojap‐affected plastids indicates that these plastids contain no ribosomes and are capable of supporting little internal membrane organization in either light or dark‐grown plants. Chloroplast mutator‐affected plastids of light‐grown plants contain some organized internal membrane structures. In dark‐grown plants, chloroplast mutator‐aftected plastids contain a crystalline prolamellar body, numerous vesicles, and osmiophilic granules. The chloroplast mutator‐affecled etioplasts display an abnormal distribution of lamellar membranes; these membranes, rather than radiating in a spokelike pattern from the prolamellar body, are condensed into a portion of the organelle. Light causes disruption of the prolamellar body in chloroplast mutator‐affected plastids without promoting the organization of a normal thylakoid membrane system. The effects of iojap and chloroplast mutator are cell autonomous and apparently influence the individual plastid, as evidenced by the persistence of heteroplastidic cells containing normal and affected plastids.
THE DEVELOPMENTAL BASIS OF ANISOPHYLLY IN SELAGINELLA MARTENSII. I. INITIATION AND MORPHOLOGY OF GROWTH
Authors: Dengler Nancy G.
Published: January 2018

The dorsiventral shoot system of Selaginella martensii is characterized by opposite pairs of ventral and dorsal leaves that are dimorphic in size and form. This study was undertaken to determine if the smaller dorsal leaf can be appropriately regarded as an arrested form of the larger leaf. Although the pattern of cell divisions and cell enlargement associated with leaf initiation is similar for both leaf types, the extent of localized growth results in distinctly larger primordia on the ventral side of the shoot. Ventral leaf primordia are also distinguished by the early formation of more extensive mesophyll tissue. Regression analysis of quantitative data on leaf length vs. position and leaf width vs. length indicates that the growth pattern of ventral and dorsal leaves is significantly different. These observations indicate that the developmental pathways of the dimorphic leaves of Selaginella martensii do not diverge at a relatively late developmental stage, but rather can be distinguished from inception.
ADAPTATION OF SUGAR MAPLE POPULATIONS ALONG ALTITUDINAL GRADIENTS: PHOTOSYNTHESIS, RESPIRATION, AND SPECIFIC LEAF WEIGHT
Authors: Ledig F. Thomas , Korbobo Donald R.
Published: January 2018

Sugar maple seeds were collected from populations spaced along two altitudinal gradients in the White Mountains of New Hampshire. When grown in a uniform environment, progeny of stands less than 0.8 km apart differed significantly in photosynthesis, respiration, and leaf characteristics, despite a lack of physical barriers to gene migration. Sugar maple is a long‐lived (200–300 yr) species with continuous distribution, but adaptive adjustment along the altitudinal gradient has occurred in only 8,000 yr, the time since colonization of the White Mountains in the wake of glacial melting. Photosynthesis was highest in progeny from high‐altitude populations, representing the species' ecological margin. High‐altitude populations also had the lowest specific leaf weight (SWL), the ratio of leaf weight to leaf area, providing a highly cost‐effective photosynthetic system, probably the result of natural selection in a short growing season. Respiration rates were also highest in populations native to high altitudes and constitute the cost of maintaining the photosynthetic machinery at high capacity. Photosynthesis tended toward a minimum and SLW to a maximum at mid‐elevations. There were parallel patterns on both gradients, suggesting parallel evolution. There were no differences among sugar maple populations in photosynthetic response to temperature, in contrast to observations on balsam fir in the same locality.
VIABILITY OF SEEDS UP TO 211 YEARS OLD EXTRACTED FROM ADOBE BRICK BUILDINGS OF CALIFORNIA AND NORTHERN MEXICO
Authors: Spira Timothy P. , Wagner Lisa K.
Published: January 2018

Seeds recovered from adobe walls of historic buildings in California and Northern Mexico were assayed for viability and germinability. Seven of the approximately 40 species tested had one or more viable seeds. These were (age of seeds in parentheses) Medicago polymorpha (200), Malva parviflora (200, 195, 183), Hordeum leporinum (200), Trifolium sp. (193), Melilotus indicus (183), Chenopodium murale (183), and C. album (143). Additionally, 41‐yr‐old seeds of Lotus corniculatus collected from living plants were found to be viable. Seeds of Medicago polymorpha and Lotus corniculatus germinated and produced normal seedlings. The importance of seed longevity in weedy species is briefly discussed.
POLLEN MORPHOLOGY AND PLANT TAXONOMY OF WHITE OAKS IN EASTERN NORTH AMERICA
Authors: Solomon Allen M.
Published: January 2018

An evaluation of possible approaches to fossil oak pollen identification utilized scanning electron microscopy to examine exine‐surface features of 171 collections, representing 16 Quercus subgenus Lepidobalanus species and varieties of eastern North America. Twenty qualitative pollen morphological characters were defined and tabulated for each of 217 pollen grains. The data were subjected to cluster analysis and cluster diagrams were compared with published white oak taxonomy. Pollen morphology and plant taxonomy compared well in series of the subgenus Lepidobalanus due primarily to consistency of character presence and absence within species and varieties. Pollen morphology of white oaks appears to reflect plant systematics above the species level. Use of routine SEM analysis to identify series of white oaks among fossil pollen grains likely will yield valid results.
ORGANELLE PRESERVATION AND PROTOPLAST PARTITIONING IN FOSSIL ANGIOSPERM LEAF TISSUES
Authors: Niklas Karl J.
Published: January 2018

Analyses of the ultrastructural states of preservation seen in fossil angiosperm mesophyll cells indicate that plastids are more commonly found in portions of protoplasts (= microprotoplasts) lacking nuclei than in microprotoplasts containing nuclei. Of the 4,498 cells examined in serial thick sections, less than 1.8% had continuous protoplasts, while the remaining 98.2% had from 2 to 3 microprotoplasts or lacked any discernable internal structure. Where nuclei and plastids were found in the same cell (21.3%), only 29.5% had these two organelles in the same microprotoplast, while 70.5% had nucleate microprotoplasts lacking plastids and enucleate microprotoplasts with well preserved plastids. Over 64% of all the cells sampled lacked nuclei but had well preserved plastids.

Neobotanical studies indicate nuclei are more stable than plastids, but during microprotoplast formation plastids are more stable in enucleate protoplasts than in those containing nuclei. Senescence and necrosis are triggered by the nuclear genome. The preferential preservation of plastids in fossil angiosperm tissues is interpreted to be the result of the isolation of part of the plastid population from nuclear control due to microprotoplast formation. This hypothesis also may explain the apparent longevity of nuclei over plastids in other fossil cells (spores, pollen, algal tissues) where protoplasmic partitioning may be less frequent.
CHROMOSOME NUMBERS IN PLATYSCHKUHRIA RYDBERG (COMPOSITAE) AND THEIR SYSTEMATIC SIGNIFICANCE
Authors: Brown Gregory K.
Published: January 2018

Diploid (2n = 12II), tetraploid, pentaploid, and hexaploid level chromosome numbers are reported for Platyschkuhria Rydb. (Compositae). First reports of accessory chromosomes in the genus are also presented. Known polyploidy in Platyschkuhria is thus far restricted to P. integrifolia (Gray) Rydb. var. desertorum (M. E. Jones) Ellison from south‐central Utah. Cytogenetic analysis, using methods and models of Jackson and Hauber (1982), suggests alloploid origins for the tetraploid levels. Diploid and polyploid populations correlate strongly with distinctively different edaphic situations, yet no consistent morphological features were identified that could justify taxonomic recognition of the polyploids.
THE ROLES OF AUXIN, ETHYLENE, AND ACID GROWTH IN FILAMENT ELONGATION IN GAILLARDIA GRANDIFLORA (ASTERACEAE)
Authors: Koning Ross E.
Published: January 2018

Filament elongation and the role of auxin in this process in Gaillardia grandiflora was investigated. Filament elongation in vivo occurred just prior to anthesis and was accompanied by cell elongation and fresh weight increase. Filaments isolated and exposed to auxin in vitro grew more rapidly than controls and their growth was comparable to that of filaments in vivo. Furthermore, the natural auxin content of disc flowers (determined by double‐standard isotope dilution analyses) increased just prior to anthesis and filament elongation. These results imply that auxin controls filament elongation. Applied ethylene slightly promoted filament elongation in vitro, and ethylene production of the flowers (determined by gas chromatography) slightly increased prior to filament growth. Fusicoccin and acidic buffers also stimulated elongation of isolated filaments. Thus, the role of auxin in controlling filament elongation in Gaillardia may involve stimulation of ethylene biosynthesis and acid growth.
THE ROLES OF PLANT HORMONES IN STYLE AND STIGMA GROWTH IN GAILLARDIA GRANDIFLORA (ASTERACEAE)
Authors: Koning Ross E.
Published: January 2018

Style and stigma elongation and stigma unfolding, and the roles of plant hormones in these processes in Gaillardia grandiflora Van Houtte were investigated. Style and stigma elongation in vivo began just after anthesis, and style elongation was accompanied by epidermal cell elongation (greatest near the stigma) and a fresh weight increase, but not by cell division or a dry weight increase. The stigma unfolded after the style and stigma elongated. Style‐stigma units excised from young disc flowers of this composite were measured as they responded to plant growth regulators applied singly, as well as in sequential and simultaneous combinations, in vitro. Style elongation was promoted by auxin, was inhibited by gibberellins and ethylene, and was unaffected by other growth regulators. Stigma elongation followed a similar pattern of response. Endogenous auxin levels and ethylene production showed parallel variation and endogenous gibberellin levels showed inverse variation with style and stigma elongation. Stigma unfolding was more sensitive to auxin applications and was promoted by applied ethylene. Ethylene production showed parallel variation and endogenous auxin levels showed inverse variation with stigma unfolding. AVG and Co2+ applications decreased auxin‐induced style elongation and fusicoccin promoted all of the growth responses of style‐stigma units in vitro. A gibberellin‐auxin‐ethylene‐acid growth interaction mode of control is proposed for these three growth processes.
STRUCTURAL INVESTIGATIONS OF ASEXUAL REPRODUCTION IN NEPHROLEPIS EXALTATA AND PLATYCERIUM BIFURCATUM
Authors: Richards Jennifer H. , Beck Judith Zenk , Hirsch Ann M.
Published: January 2018

Nephrolepis exaltata cv. Bostoniensis, the Boston fern, exhibits extreme stem dimorphism. The plant has orthotropic, dictyostelic shoots which bear pinnatifid leaves and plagiotropic, protostelic stolons which are aphyllous. Vegetative reproduction occurs by budding from primary and secondary stolons. Secondary stolons arise exogenously from derivatives of the apical cell of the primary stolon, whereas root primordia develop endogenously. Shoots develop in vivo when a creeping stolon makes contact with the substrate via extensive root proliferation. When stolon segments are excised and grown in vitro, secondary stolon primordia expand and initiate leaf primordia, forming new leafy shoots. In Platycerium bifurcatum, the staghorn fern, asexual propagation occurs on ageotropic roots ramifying among the basal nest fronds. Root bud initiation is marked by root tip hypertrophy following cortical parenchyma expansion. Root apical cell derivatives produce the bud apex; the root apical cell remains separate from the developing root bud. Superficially, vegetative reproduction in Nephrolepis and Platycerium appears to involve unusual organs. However, both ferns exhibit leafy bud development from distinct sites of origin, not from undetermined primordia or from direct transformation of root to shoot. Thus, distinctness of organ types is maintained in these two ferns and no evidence for interconvertibility of organ types has been found.
EXINE DEVELOPMENT IN GERBERA JAMESONII (ASTERACEAE: MUTISIEAE)
Authors: Southworth Darlene
Published: January 2018

The development of the pollen wall inGerbera jamesoniiwas studied using light and electron microscopy and histochemical stains. The primexine is patterned while the microspores are encased in the special cell wall. Bacules form at projections of the plasma membrane. Numerous ribosomes and large, single‐membrane bound vesicles containing fibrillar material are observed near the developing bacule bases. The tectum and nonhomogeneous layer form simultaneously with the bacules, but do not appear to be outgrowths of them. Following dissolution of the callose cell wall, the lamellate exine‐2 is laid down beginning in the apertural region. Polysaccharides are associated with the developing exine‐1 and the pore regions of the exine‐2. After exine‐2 deposition, the exine‐1 thickens by the addition of sporopollenin. When the exine is completed, a vacuole forms which displaces the nucleus, compresses the exine‐2 and expands the incurved exine‐1. As the vacuole shrinks, the intine and storage polysaccharides form.
ON THE EMBRYOGENY OF SCHIZAEA DICHOTOMA
Authors: Bierhorst David W.
Published: January 2018

The zygote of Schizaea dichotoma divides transversely and the outer cell thus produced divides longitudinally. The three cells probably establish the organs: root, stem, and foot. The first leaf is not embryonic in origin but forms on the relatively old sporeling. Some general comments on gametophyte and embryo phylogeny are presented.