bluuebunny/crossref_metadata_2025 huggingface dataset:
AUREALCAULIS CROSSII GEN. ET SP. NOV., AN ARBORESCENT, OSMUNDACEOUS TRUNK FROM THE FORT UNION FORMATION (PALEOCENE), WYOMING
Authors: Tidwell William D. , Parker Lee R.
Published: January 2018

Aurealcaulis crossii gen. et sp. nov., is based on permineralized trunks of an osmundaceous tree fern from the Paleocene Fort Union Formation from near Bitter Creek Station of southwestern Wyoming. This new species is characterized by centripetal (exarch) development of its xylem strands which form part of the leaf traces. Most of the leaf traces depart the stele as two segments that fuse into a single C‐shaped petiole vascular strand outside of the outer cortex. Stipular expansions of the petiole bases of this species lack sclerenchyma, and roots arise from the lateral edges of leaf traces in the inner cortex. The family Osmundaceae and subfamily Osmundoideae are slightly emended to accept genera assignable to this family and subfamily with exarch protoxylem in their steles. Foliage similar to Osmunda greenlandica (Heer) Brown, which is possibly the leaf form of A. crossii, occurred next to an axis of this species which was in growth position. This axis was anchored in a lignite suggesting that this species grew under swampy conditions. Aurealcaulis crossii is the first arborescent member of the Osmundaceae of Tertiary age and the second arborescent form in this family reported from the Northern Hemisphere.
PALYNOLOGY AND SYSTEMATICS OF THE LYTHRACEAE. II. GENERA HAITIA THROUGH PEPLIS
Authors: Graham Alan , Nowicke Joan W. , Skvarla John J. , Graham Shirley A. , Patel Varsha , Lee Sangtae
Published: January 2018

Pollen morphology for 12 genera of the Lythraceae is described, using light microscopy (LM), scanning (SEM) and transmission electron microscopy (TEM). The genera surveyed are Haitia, Heimia, Hionanthera, Lafoensia, Lagerstroemia, Lawsonia, Lythrum, Nesaea, Orias (= Lagerstroemia), Pehria, Pemphis, and Peplis. Among results of taxonomic significance are 1) the similarity of pollen between Haitia and Ginoria, suggesting that future classifications reflect a close relationship between these genera, 2) a comparable similarity in pollen between Pehria and Adenaria, 3) the distinction of Hionanthera pollen from that of Ammannia, 4) an exine similar in certain ultrastructural characteristics between Orias and some species of Lagerstroemia, although in general aspect they appear quite different, 5) that within the Didiplis‐Lythrum‐Peplis complex, there are three palynologically distinct groups, with Didiplis standing apart from the somewhat more similar, but nevertheless, distinct Lythrum and Peplis, and 6) that considerable differences exist between pollen of Pemphis acidula and Pemphis madagascariensis, supporting removal of the latter species to a new genus. This pollen survey is part of a multi‐disciplinary effort to clarify generic limits in the Lythraceae, and evaluate relationships within the family and among families of the Myrtales.
A BENEFICIAL GAS TRANSPORT SYSTEM IN NYMPHOIDES PELTATA
Authors: Grosse Wolfgang , Mevi‐Schütz Jovanne
Published: January 2018

The aquatic vascular plant Nymphoides peltata (Gmel.) O. Kunze which inhabits anaerobic environments depends highly on the availability of oxygen for its submerged organs buried in the sediment of the lake. In tracer gas studies, carried out with shaded plants, it is shown that ethane is taken up by one of the youngest leaves in a whorl and transported down the petiole to the axis, returning to the surface via the older leaves. In sunlight, this gas diffusion through the plant is replaced by an effect which enhances the gas movement up to 1,200% due to the increased difference between leaf temperature and the surrounding air (ΔT = 1.7 K). The temperature difference is accompanied by a pressurization 50 Pascal above ambient inside the aerenchyma of the young leaves. These findings confirm that a pressurized flow‐through system is established by N. peltata, whereby the oxygen supply to the rhizomes is improved. The temperature difference derived from irradiation energy initiates a circulating air stream, which transports air from the young leaves through the plant. Enhanced transport of a tracer gas as well as oxygen can be demonstrated by warming an excised young leaf with red‐filtered light or warm water. A similar increase in gas transport is not detected through older leaves. The light energy needed to create a temperature difference can be substituted with warm water. Evidence is thus given, which shows that the increased oxygen emission from the petiole of young leaves is independent of photosynthesis. This gas transport is a result of thermo‐osmosis under slip‐flow conditions (Knudsen diffusion), limiting this effect to a temperature gradient between the surrounding air and the lacunar air of young leaves.
ELECTROPHORESIS IS MODIFYING OUR CONCEPTS OF EVOLUTION IN HOMOSPOROUS PTERIDOPHYTES
Authors: Haufler Christopher H.
Published: January 2018

Analyses of electrophoretically detectable enzyme variants in homosporous pteridophytes are facilitating the development of new insights into their genetics and evolution. The number of isozymes per enzyme indicates that homosporous pteridophytes are genetic diploids, in spite of the fact that they have high chromosome numbers. High levels of heterozygosity and genetic variability in sporophytic populations indicate that many diploid species are outcrossing with inbreeding representing a derived character state. Because the congeneric homosporous pteridophyte species analyzed to date have low genetic identities, allozymic characters are also proving to be useful as genomic markers for elucidating patterns of reticulate evolution.

The accumulated data suggest that the genetic system of homosporous pteridophytes differs fundamentally from that of seed plants. The present genomic constitution of extant taxa may be the result of repeated cycles of allopolyploidy followed by gene silencing and extinction of progenitor taxa. Alternatively, the original homosporous pteridophytes may have had high chromosome numbers. Although current species probably evolved recently, their phylogenetic roots may be difficult to trace because even closely related pteridophytes are genetically distant and extinction has obliterated the ancestral intermediates between lineages. These hypotheses can and should be tested using a combination of molecular, phylogenetic, and population biology methods.
A POSSIBLE ROLE FOR ETHYLENE DURING IAA‐INDUCED POLLEN EMBRYOGENESIS IN ANTHER CULTURES OF SOLANUM CAROLINENSE L
Authors: Reynolds Thomas L.
Published: January 2018

Pollen embryogenesis in Solanum carolinense was induced by culturing anthers containing bicellular pollen grains on medium supplemented with indole‐3‐acetic acid (IAA). Pollen embryogenesis was also promoted by Ethrel and the ethylene precursor, aminocyclopropane carboxylic acid (ACC), although not to the same degree as IAA alone. Furthermore, IAA stimulated ethylene accumulation in culture to the same extent as did Ethrel and ACC. It is suggested that IAA induced pollen embryogenesis at least partially, through auxin‐mediated ethylene production. However, since CoCl2, an inhibitor of ethylene synthesis, reduced the amount of ethylene in IAA‐treated cultures but did not eliminate the formation of pollen embryos, IAA also appears to have a direct effect on morphogenesis in anther cultures.
SEASONAL SECONDARY GROWTH IN NEEDLE LEAVES OF PINUS STROBUS AND PINUS BRUTIA
Authors: Ewers Frank W. , Aloni Roni
Published: January 2018

Mature needles and elongating current year's needles of Pinus strobus growing in Massachusetts and P. brutia growing in Israel were collected monthly or bimonthly for seasonal analysis of leaf cambial activity. Mature needles produced secondary phloem but no xylem, and, regardless of the season, had a cambial zone from 2 to 3 cell layers wide. In the current year's needles maturation was basipetal and the procambium differentiated into primary xylem, primary phloem, and the phloem‐producing vascular cambium before needle maturity. One‐ and 2‐year‐old needles of Pinus strobus produced slightly over 4 cell layers of phloem between April 15 and September 1 of 1983, with a peak production rate of about 2 cell layers per month in May and early June. One‐year‐old needles of P. brutia produced about 6 phloem cell layers in 1983, with phloem being produced throughout the year except in midsummer. This was contrasted by fall and winter dormancy in needles of P. strobus.
HYBRIDIZATION IN THE BABASSU PALM COMPLEX: I. ORBIGNYA PHALERATA × O. EICHLERI
Authors: Balick Michael J. , Pinheiro Claudio U. B. , Anderson Anthony B.
Published: January 2018

The babassu palm (Orbignya phalerata) is an important source of oil and charcoal in Brazil. In some areas it grows in association with O. eichleri, and where their distribution is sympatric, a third palm is found. This taxon was described by Bondar in 1954 as O. teixeirana. As a result of intense fieldwork and subsequent morphological and anatomical studies, we conclude that O. teixeirana is a hybrid between O. phalerata and O. eichleri and propose a change in its status to reflect this new understanding of its origin.
PATTERNS OF BIOMASS ALLOCATION IN SPINACIA OLERACEA (CHENOPODIACEAE) ACROSS A SALINITY GRADIENT: EVIDENCE FOR A NICHE SEPARATION
Authors: Vitale Jeffrey J. , Freeman D. Carl , Merlotti Lori A. , D'Alessandro Michael
Published: January 2018

Spinacia oleracea var. Americana was hydroponically grown across an experimental salinity gradient ranging from 0.0 to 6.0 grams NaCl/liter nutrient medium. Twenty male, 20 female, and 20 monoecious plants were randomly harvested from each treatment where possible. Root biomass (RTA), biomass allocated to leaves and stems (VA), and reproductive biomass (RA) were determined. Male, female, and monoecious plants were shown to have significantly different patterns of RTA, VA, and RA. Moreover, the treatments influenced allocation patterns of the sexes differently, i.e., a partial niche separation was observed among the sexes along the gradient with respect to RTA, VA, and RA. Additionaly, the sexes expressed different trade‐offs between allocation of resources to the different tissues; most notably, under high salinity, RTA, and RA were strongly negatively correlated in females, but positively correlated in male and monoecious plants.
COMPARATIVE MORPHOLOGY OF THE CAPITULUM OF ENCELIOPSIS (ASTERACEAE: HELIANTHEAE)
Authors: Sanders Donald L. , Clark Curtis
Published: January 2018

Features of the capitula of all four species of Enceliopsis were examined with light and scanning electron microscopy, measured, and subjected to univariate analysis. Differences were found in the complement, distribution, and density of trichomes, the size of the receptacle, ray ligule, and disk corolla tube, and the size and shape of the phyllaries, paleae, disk corolla throats, and achenes. Morphology of trichomes, phyllaries, and achenes, as well as other vegetative characteristics, show that E. nudicaulis, E. covillei and E. argophylla form a group separate from E. nutans. Features of the achene suggest affinity of the former group with Geraea, whereas features of the trichomes and achene of E. nutans support affinity with Encelia. Characters of the receptacle, paleae, ray and disk corollas, and achene clearly show that E. nudicaulis, E. covillei, and E. argophylla are distinct.
CAPSULE WALL ANATOMY IN RELATION TO CAPSULAR DEHISCENCE IN LUDWIGIA SECT. MICROCARPIUM (ONAGRACEAE)
Authors: Peng Ching‐I , Tobe Hiroshi
Published: January 2018

Ludwigia sect. Microcarpium is a polyploid complex of 15 taxa that occur mainly in wet habitats of the southeastern United States. In previous treatments, plants of this section were described as having capsules that dehisced by the separation of the walls from the indurate disc (ring dehiscence). Two additional types of dehiscence are reported in this study. The capsules of some species dehisce by the irregular disintegration of the outer capsule wall (peeled dehiscence), while in another group, they dehisce by four longitudinal, lenticular slits and finally into four basally united parts (loculicidal dehiscence). Each of the different patterns of capsular dehiscence was found to have a distinctive anatomical basis. The loculicidal‐dehiscent and peeled‐dehiscent capsules apparently evolved from the ring‐dehiscent type of capsule independently, and each of these derived types appears to delimit a natural evolutionary unit.
LEAF AND SHOOT DEMOGRAPHY IN BACCHARIS SHRUBS OF DIFFERENT AGES
Authors: Hobbs R. J. , Mooney H. A.
Published: January 2018

Studies of leaf and shoot demography and growth in Baccharis pilularis ssp. consanguinea indicated that shoot mortality and rates of leaf loss were higher in older shrubs. Shoot elongation was greatest in summer and rates of leaf loss and litterfall highest in winter. Leaf addition was greatest in spring and fall, corresponding to periods of favorable temperature and moisture conditions.
ASSOCIATION OF MUCILAGE WITH THE LIGULE OF SEVERAL SPECIES OF SELAGINELLA
Authors: Bilderback D. E.
Published: January 2018

Mucilage bodies of protein and some polysaccharide were closely associated with ligules of Selaginella kraussiana (Kunze) A. Braun grown in the greenhouse, and Selaginella wallacei Hieron. and Selaginella oregana D.C. Eat. from natural habitats. With S. wallacei and S. oregana, several mucilage bodies were associated with some ligules. No mucilaginous material was associated with the ligules of Selaginella douglasii Hook, et Grev., Selaginella densa Rydb. or Selaginella apoda (L.) Fernald from natural habitats. When stem tips of S. kraussiana and S. douglasii were placed in sterile culture on a medium with sucrose, massive amounts of mucilage appeared around the ligules in the tight interstices of the stem tip leaves and extended out on the surface of the leaves. The mucilage from a cultured stem tip of S. kraussiana contained 0.034 μgm of protein, 14.6 μgm of apparent glucose equivalents as polysaccharide and no significant amounts of phenolics. In stem tips with tightly appressed leaves, either ligules or young leaves could have produced the mucilage; however, in more mature regions of the stem where internodal elongation had separated the leaves, mucilage coated only the apical portions of the ligules and was not associated with leaves. No other possible source of mucilage (bacteria or fungi) was detected among the leaves. When stem tips of S. wallacei, S. densa and S. apoda were placed in culture, mucilage was not produced. Since mucilage is closely associated with the ligule of some species of Selaginella growing in nature, the greenhouse, or tissue culture, the ligule may be glandular.
PALEOZOIC SEED FERNS: HETERANGIUM KENTUCKYENSIS SP. NOV., FROM THE UPPER CARBONIFEROUS OF NORTH AMERICA
Authors: Pigg Kathleen B. , Taylor Thomas N. , Stockey Ruth A.
Published: January 2018

Heterangium kentuckeyensis sp. nov. is described from Lower/Middle Pennsylvanian sediments of eastern Kentucky, based on permineralized stems, petioles, frond members, laminar foliage, and roots, including several organs in attachment. Stems 2.2 to 5.8 mm in diameter are known in several developmental stages. The considerable variability in stelar and cortical histology within this one species emphasizes the need to reassess variability within previously described taxa. Fronds of H. kentuckyensis are at least twice pinnate and bear primary pinnae alternately at approximately right angles. Laminar pinnules have dichotomous venation, are at least 2‐lobed, and comparable to foliage of the Sphenopteris‐type. Stomata possess 6–7 subsidiary cells with abaxial papillae. The characters used to distinguish the subgenera of Heterangium are evaluated and found to be unreliable. Moreover, suggested phylogenetic schemes both within Heterangium and between this taxon and other lyginopterid pteridosperms based on these features are inconsistent with stratigraphic data. Until reproductive features are known, the classification of Heterangium species is best based on characters of the vegetative sporophyte, including stelar organization (particularly protoxylem architecture), cortical histology, and frond morphology.
INITIATION OF TERPENOID SYNTHESIS IN OSMOPHORES OF STANHOPEA ANFRACTA (ORCHIDACEAE): A CYTOCHEMICAL STUDY
Authors: Curry Kenneth J.
Published: January 2018

The floral scent glands (osmophores) of Stanhopea produce a fragrance composed of terpenoids and aromatics which attract pollinators. The terpenoid component is composed of isoprene units synthesized via the mevalonic acid pathway. Localization of hydroxymethylglutaryl CoA synthase in the mevalonic acid pathway was achieved using a technique which elicits the formation of an electron‐dense precipitate of uranyl ferrocyanide at the point in the mevalonic acid pathway where an acetyl group from acetyl CoA is transferred to acetoacetyl CoA, releasing free CoA‐SH. Applying this technique to cells of the osmophore of 5. anfracta resulted in a precipitate between the inner and outer mitochondrial membranes, in the smooth endoplasmic reticulum, and, to a lesser extent, on the outer surface of the tonoplast membranes and between the inner and outer membranes and granal membranes of amyloplasts indicating multiple, subcellular locations for at least some enzymes in the mevalonic acid pathway. Localization of carnitine acetyltransferase by a similar technique resulted in a precipitate between the inner and outer mitochondrial membranes and in the smooth endoplasmic reticulum indicating multiple, subcellular locations for this enzyme also.
DIVERSITY OF SHOOT ORGANIZATION IN THE ARACEAE
Authors: Ray Thomas S.
Published: January 2018

Morphological units in the Araceae are discussed and defined. The fundamental unit is the segment (an internode and its leaf or leaves), of which there are two basic types, the monopodial segment and the branching segment. Segments are assembled into chains to form articles (also called axes), which terminate in inflorescences, and are the product of the activity of a single apical meristem. Successive articles are assembled into chains which are physiognomically unbranched shoots. Shoot organization in the Araceae is discriminated into types on the basis of five characteristics: whether the shoot is renewed after flowering, whether renewal axes are proleptic or sylleptic, whether renewal axes develop from an axillary position, whether renewal axes have a variable or a constant number of leaves, and the number of leaves on renewal axes with a constant leaf number. The types of growth are described, illustrated, and organized into a hierarchical scheme, and a terminology is provided. A list of species representing each of the types is given.
APOMIXIS IN THE POA SECUNDA COMPLEX
Authors: Kellogg Elizabeth A.
Published: January 2018

Observation of cleared ovules of Poa secunda Presl showed that plants produce aposporous embryo sacs, and emasculation studies showed that they do not set seed without pollen. The ratio of sexual to asexual embryo sacs on a given plant does not correlate with percent stainable pollen, nor does pollen stainability correlate with meiotic regularity or with chromosome number. Percent apomictic ovules, percent pollen stainability, and regularity of meiosis all vary within a given population; they also vary if the same plant is moved from one site to another. Although there is morphological variation in the species, none of the reproductive features correlates with morphology. Pollen from any morph will stimulate seed set in any other morph, and hybrids have been produced in low frequency. Plants will also set seed using their own pollen. In its reproductive biology, P. secunda exhibits many similarities with P. pratensis L.
KARYOLOGICAL AND ISOZYME VARIATION IN WEST INDIAN AND ALLIED AMERICAN MAINLAND RACES OF MAIZE
Authors: Bretting P. K. , Goodman M. M. , Stuber C. W.
Published: January 2018

The maize races (Zea mays L.) of the West Indies have considerable historic and economic importance. The present study reports the isozyme variation in these races and selected collections of related South and Central American races. These data were subjected to cluster and principal component analyses in conjunction with isozyme data previously collected for other mainland races. Karyological descriptions from more than 200 accessions of West Indian and related races were taken from previous studies by McClintock and co‐workers and were analyzed with the same statistical techniques used for the isozyme data. Viewed together, isozyme and karyological evidence revealed that the evolutionary history and systematic relationships of these races were complicated. The West Indian races formed a distinct supraracial group with affinities especially to races from the Caribbean coast of South America and the Central American lowlands. Geographic variation in the chromosome morphology of West Indian races seemed strongly associated with colonial history. Two races, Early Caribbean and St. Croix, were not very closely related to other West Indian races. Haitian Yellow was more distantly related (especially karyologically) to other West Indian races than its morphology would suggest. It is suggested that Cuban Flint is an indigenous Cuban race rather than simply a South American Cateto recently introduced to Cuba. Chandelle was highly variable and had affinities to coastal South American races, Cuban Flint, and Coastal Tropical Flint. The latter race was more closely related to Cuban Flint and Chandelle than to Tusón, which karyologically strongly resembled lowland Central American races but isozymatically resembled coastal South American races.
SPATIAL PATTERNS OF SEED DISPERSAL AND POSTDISPERSAL SEED PREDATION OF CRYPTANTHA FLAVA (BORAGINACEAE)
Authors: Casper Brenda B.
Published: January 2018

I examined the spatial patterns of seed dispersal and postdispersal seed predation of the semidesert perennial Cryptantha flava (A. Nels.) Payson (Boraginaceae) at two sites in north‐eastern Utah. Most flowers mature only one seed (nutlet) which is permanently retained within a pubescent calyx. The calyx and enclosed seed abscise from the plant as a unit. These dispersal units are effectively dispersed by wind as evidenced by the highly directional seed shadows and the long distances some of them travel (up to 31.3 m). Potential seed predators at the sites include five species of rodents, of which Peromyscus maniculatus is the most common, and two species of ants, Pogonomyrmex occidentalis and an undescribed species of Conomyrma. There were no strong spatial patterns of postdispersal seed predation. More seeds were removed from dishes placed at the bases of fruiting adults than from dishes ≥ 1.0 m away in one of three experiments. More seeds were removed from under shrubs or clumps of grass than in the open in one of four experiments. After 3–4 days, there was a consistent tendency for more seed removal from high density (75 seeds per .25 m2) quadrats than from low density (75 seeds per 6.25 m2) quadrats, but the difference was not always significant. There was a similar nonsignificant difference between high‐ and low‐density quadrats exposed for 21 days. The pubescent calyx greatly discourages seed predation by ants, and probably also reduces predation by rodents. In addition, by increasing the surface area of the dispersal unit, the calyx may facilitate dispersal by wind.
INHIBITION OF FERN SPORE GERMINATION BY LIPOPHILIC SOLVENTS
Authors: Miller John H.
Published: January 2018

Several alcohols and other solvents inhibit germination of spores of the fern, Onoclea sensibilis L. The inhibition is reversible when spores are transferred to solvent‐free media. The effectiveness of different solvents, measured by the concentration needed to inhibit germination by 50%, increases with their lipid solubility. The activity of straight‐chain alcohols from methanol through n‐heptanol is highly correlated with lipid solubility, whereas the correlation is weaker for several other solvents. The results indicate that some lipophilic site in the spore is important in germination.
ENDOPHYTE‐HOST ASSOCIATIONS IN FORAGE GRASSES. VIII. HETEROTHALLISM IN EPICHLOË TYPHINA
Authors: White James F. , Bultman Thomas L.
Published: January 2018

Experiments conducted indicate the mating system in Epichloë typhina to involve simple bipolar heterothallism. Perithecia were formed when condia were transferred to a compatible stroma. Perithecial development followed the growth of mycelium over the surface of the stroma. The perithecial stroma consisted of two layers: an inner layer composed of the original mycelium of the conidial stroma and an outer layer that appears to be composed of mycelium growing from the inner stromal layer. Perithecia were initiated in the outer layer, just above the interface of the two layers. Natural onset of perithecial formation was associated with evidence of visitation by a prasitic fly (Phorbia phrenione).
EFFECTS OF FIRE ON CLONAL GROWTH AND DYNAMICS OF PITYOPSIS GRAMINIFOLIA (ASTERACEAE)
Authors: Hartnett David C.
Published: January 2018

The rhizomatous perennial Pityopsis graminifolia was studied in a Florida sandhill community in an annually burned site, a periodically burned site, and a site that has been protected from fire since 1965. These different fire regimes significantly affected the demography and life histories of both plants and plant parts in this clonal species. Fires resulted in reductions in ramet biomass and height, and an increase in the (root + rhizome)/shoot biomass ratio. Burning also decreased the total number of flower heads and new rhizomes produced per ramet. However, the survivorship of initiated rhizomes was greater in burned sites and resulted in a larger number of established daughter ramets per clone. As a result, in burned sites there was a shift in clone structure toward larger numbers of smaller ramets, but there were no significant reductions in seed or rhizome production on a per genet basis.

The results showed that the responses to fire in P. graminifolia are different when measured at the genet vs. ramet level and that the effects of fire on clones can be explained by demographic responses of plant parts. Population regeneration in the study sites was dependent on successful clonal ramet production because no seedling recruitment was observed. This suggests that disturbances other than fire are important for new genet recruitment in these clonal populations.
PATHOGEN IMPACT ON SEXUAL VS. ASEXUAL REPRODUCTIVE SUCCESS IN ARISAEMA TRIPHYLLUM
Authors: Parker Matthew A.
Published: January 2018

Populations of Arisaema triphyllum commonly harbor a systemic fungal pathogen, Uromyces ari‐triphylli, which reduces leaf area and leaf longevity. Infected plants produced 42% fewer asexual progeny (cormlets). Furthermore, all asexual progeny from infected parents were themselves infected with Uromyces. Mean seed production of infected plants was only 21% of that among healthy plants. A hand pollination experiment demonstrated that 1) infected male plants can produce viable pollen, 2) the low seed production of naturally pollinated infected females was not due to inadequate pollination, and 3) seed production among healthy female plants was strongly pollinator limited. Seeds from infected and healthy parents had similar viability, and all seeds germinating from both types of parents were uninfected. The contrast in disease transmission to sexual vs. asexual progeny suggests that pathogen attack may be one selective factor favoring sexual reproduction in A. triphyllum populations.
PRESENCE OF VESSELS IN WOOD OF SARCANDRA (CHLORANTHACEAE); COMMENTS ON VESSEL ORIGINS IN ANGIOSPERMS
Authors: Carlquist Sherwin
Published: January 2018

Sarcandra is the only genus of Chloranthaceae hitherto thought to be vesselless. Study of liquid‐preserved material of S. glabra revealed that in root secondary xylem some tracheary elements are wider in diameter and have markedly scalariform end walls combined with circular pits on lateral walls. Examination of these wider tracheary elements with scanning electron microscope (SEM) demonstrated various degrees of pit membrane absence in the end walls. Commonly a few threadlike fibrils traverse the pits (perforations); these as well as intact nature of pit membranes in pits at ends of some perforation plates are evidence that lack of pit membranes does not result from damage during processing. Some perforations lack any remnants of pit membranes. Although perforation plates and therefore vessels are present in Sarcandra roots, no perforations were observed in tracheary elements of stems or lignotubers. Further, stem tracheids do not have the prominently scalariform end walls that the vessel elements in roots do. Presence of vessels in Sarcandra removes at least one (probably several) hypothetical events of vessel origin that must be postulated to account for known patterns of vessel distribution in angiosperms, assuming that they are primitively vesselless. Seven (perhaps fewer) vessel origin events in angiosperms could account for these patterns; two of those events (Nelumbo and monocotyledons) are different from the others in nature. Widely accepted data on trends of vessel specialization in woody dicotyledons yield an unappreciated implication: vessel specialization has happened in a highly polyphyletic manner in dicotyledons, and therefore multiple vessel origins represent a logical extension backward in time. If a group of vesselless dictyoledons ancestral to other angiosperms existed, they can be hypothesized to have had a relatively homogeneous floral plan now that Sarcandra‐like plants no longer need be imagined within that group. Sarcandra and other Chloranthaceae show that the borderline between vessel absence and presence is less sharp than generally appreciated.
GROWTH AND DEVELOPMENT OF THE MALE GAMETOPHYTE OF GINKGO BILOBA WITHIN THE OVULE (IN VIVO)
Authors: Friedman William E.
Published: January 2018

The mature male gametophyte of Ginkgo biloba can be divided into two regions: a large saccate structure that is suspended within the fertilization chamber above the archegonia, and a pervasive, highly branched haustorial system that ramifies through the intercellular air spaces of the apex of the nucellus. This morphology appears to differ in many ways from the simpler more typical male gametophytes of most other groups of seed plants.

Growth and development of the male gametophyte of Ginkgo biloba were studied using computer reconstruction techniques to generate images of the gametophyte from data derived from serial sections through the ovule. These investigations reveal that morphological development of the male gametophyte of Ginkgo biloba is divided into three distinct phases: 1) Germination, characterized by an initial brief period of diffuse growth. This phenomenon has not been described for any other seed plant male gametophyte; 2) Initiation of tip growth and the formation of a tubular body, as typifies all seed plant male gametophytes. In Ginkgo, this is accompanied by a high degree of branching, giving rise to an extensively branched haustorial system; 3) Late swelling of the proximal unbranched portion of the gametophyte resulting in formation of the saccate structure that is characteristic of the mature gametophyte. This process appears to be very similar to late development in cycad male gametophytes.

Thus, despite the seemingly anomalous morphology of the mature male gametophyte of Ginkgo biloba, specific patterns of growth and development are in many ways similar to growth processes expressed by the male gametophytes of some or all major groups of seed plants.
MIOCENE COMMUNITIES AND PALEOENVIRONMENTS OF SOUTHERN COSTA RICA
Authors: Graham Alan
Published: January 2018

Fossil palynomorphs representing 40 taxa have been recovered from lower(?) Miocene (Uscari sequence) deposits in southern Costa Rica. Three paleocommunities are suggested for the vicinity of the depositional basin—coastal mangrove (Rhizophora); some form of the lowland wet forest (Phaeoceros, Cnemideria, Bombacaceae, Alchornea, cf. Glycydendrum, cf. Banisteriopsis, Hiraea, Myrtaceae (Eugenia/Myrcia type), and Melastomataceae); and especially the midaltitude (1,000–2,000 m) cloud forest (Lycopodium, Selaginella, cf. Hymenophyllum, Lophosoria, Pityrogramma, Pteris, Podocarpus (common), Ilex, Ericaceae (Cavendishia type), and Lisiantehus). Absent are members of higher altitude communities, and vegetation of drier to arid aspect. Savannahs, important in the interchange of mammalian faunas between North and South America, remain undetected in Gulf/Caribbean Tertiary floras. Paleoenvironments are estimated as wet tropical, similar to present‐day conditions, with a less diverse and insular paleophysiography accounting principally for differences between the early Miocene and modern life zones. This is in contrast to the Paraje Solo assemblage from Veracruz, Mexico, which reflects distinctly cooler climates in the late Miocene. These results are consistent with plate tectonic models for the Gulf/Caribbean region, and emerging global paleotemperature patterns derived from 18O studies of marine invertebrates.
FIRST FOSSIL EVIDENCE FOR THE PRIMITIVE ANGIOSPERM FAMILY LACTORIDACEAE
Authors: Zavada Michael S. , Benson James M.
Published: January 2018

Pollen of the primitive angiosperm family Lactoridaceae has been recovered from Turonian‐Campanian (Upper Cretaceous) sediments from eleven boreholes off the southwest coast of southern Africa. This is the first report of the Lactoridaceae in the fossil record. The one extant species of the Lactoridaceae is confined to the Juan Fernandez Islands located off the coast of Chile. The occurrence of lactoridaceous pollen in Cretaceous deposits of southern Africa suggest that this primitive angiosperm family may have been more widespread in the Southern hemisphere during the Cretaceous.
EOCENE FLORAL EVIDENCE OF LAURACEAE: CORROBORATION OF THE NORTH AMERICAN MEGAFOSSIL RECORD
Authors: Taylor David Winship
Published: January 2018

Numerous megafossils of Lauraceae have been reported from the early Tertiary of North America, but the subfamilial affinities are usually not well understood due to the great morphological variability found in extant taxa. The flowers of Androglandula tennessensis gen. et sp. nov. Taylor, from the Middle Eocene Claiborne Formation, are six‐parted, pedicellate, bracteate, and have stamens with paired basal staminal glands. The flowers have ethereal oil cells and paracytic stomates throughout. The fossil species has affinities with the subtribe Cinnamomineae, and this supports suggestions that the Middle Eocene climate of the southeastern U.S. was subtropical. The existence of this fossil, and reports of the subtribe from the Eocene of Europe, indicate a South American‐North American‐European‐southeast Asian paleodistribution suggesting that extinction in North America and Europe was the cause of the tribe's current disjunct distribution.
ALLELOPATHIC POTENTIAL OF RASPBERRY FOLIAR LEACHATES ON GROWTH OF ECTOMYCORRHIZAL FUNGI ASSOCIATED WITH BLACK SPRUCE
Authors: Coté Jean‐Francois , Thibault Jean‐Robert
Published: January 2018

In vitro bioassays on seven species of ectomycorrhizal fungi associated with black spruce (Picea mariana (Mill.) BSP) were tested under allelopathic action of raspberry (Rubus idaeus L.). Radial growth inhibitions were observed when fungi were confronted with increasing concentrations (0%–0.1%–0.5%–2.5%) of foliar leachates made from May, July, and September material (1986). For the 2.5% treatment, species Paxillus involutus, Laccaria proximo, Laccaria bicolor, Thelephora terrestris, and Cortinarius pseudonapus grew only 6, 8, 32, 42, and 46% of their control, whereas Hebeloma cylindrosporum and Cenococcum geophilum were stimulated. Tree seedlings from raspberry invaded plantation showed mycorrhizal infection rate over 75%, with fine roots mainly colonized by C. geophilum. In combination with efforts of tree improvement and based on the results of this study, it seems important to select a well‐adapted my‐corrhizae, when interference by raspberry is involved.
POPULATION PERSISTENCE AND REPRODUCTIVE ECOLOGY OF A FOREST HERB: ASTER ACUMINATUS
Authors: Hughes Jeffrey W. , Fahey Timothy J. , Bormann F. Herbert
Published: January 2018

Aster acuminatus Michaux, a patchily distributed herb of eastern forests, is commonly represented in all stages of forest succession. To determine its mechanisms of persistence, we carefully examined the distribution patterns of this species as affected by its reproductive ecology and demography. Using A. acuminatus as a model, we hypothesized that 1) availability of propagules and location of adequate recruitment sites impose first‐order control over plant distributions in stands of all ages by determining where plants might be found and 2) light and other resources exert a second‐order control over herb distributions by determining where established plants cannot persist. Results from our study at the Hubbard Brook Experimental Forest in New Hampshire demonstrated this species' ability to exploit resource‐rich disturbances through immediate and profuse ramet and seed production. This ensured rapid colonization of new sites and provided genetic exchange for longer‐term survival. Relict colonies which survived the disturbance served as the sole propagule‐producing loci for the first year of colonization. After several years, resources became more limiting and the aster shifted to a more conservative asexual reproduction strategy which provided population stability until the next disturbance. The clumped distribution of A. acuminatus in mature forests is explained by strict adherence to asexual ramet replacement in which there is no year‐to‐year change in aster importance. Location of persistent colonies probably is dictated by location of suitable seedbeds during the first few years of recovery after disturbance. Whereas numerous sites may be colonized initially, timing of colonization and quality of site impose constraints on which colonies persist.
POLLINATION OF RAFFLESIA (RAFFLESIACEAE)
Authors: Beaman Reed S. , Decker Pamla J. , Beaman John H.
Published: January 2018

The genus Rqfflesia includes about 13 species of parasitic flowering plants, among which are the largest known flowers. The flower with subtending scales is the only part of the plant external to the host and is produced solitary on roots (rarely stems) of the genus Tetrastigma (Vitaceae). Field studies were made of the pollination process in R. pricei, a species endemic to the Crocker Range in the Malaysian state of Sabah (northern Borneo). Pollination is mediated by carrion (bluebottle) flies of the genera Lucilla and Chrysomya. Experimental data indicate that both visual and olfactory cues are important in attracting flies to flowers. Flies (mostly female L. papuensis) obtain loads of the viscous liquid pollen matrix by visiting male flowers and entering anther grooves on the central column of the flower, precisely guided by ridges armed with hairs that force the fly into a position in which the pollen is positioned on the dorsal part of the thorax. “Windows” on the inside of the perigone diaphragm apparently help orient their flight inside flowers. Pollen‐loaded flies visiting female flowers may enter the infradiscoidal sulcus formed by a broad ring of stigmatic tissue above and the expanded base of the column below. On entering the sulcus the fly is wedged in so tightly that pollen is rubbed off the thorax onto the stigma. Only large flies could be effective in picking up pollen from male flowers and transferring it to female flowers. The pollination syndrome is sapromyophily, in which the flower closely parallels trap flowers of several other plant families, although it is not a trap. The flower provides no reward for pollinators but deceives them by an apparent offering of food and possibly brood place. Rafflesia plants are extremely rare, perhaps in part because of infrequency of pollination, which requires neighboring male and female flowers simultaneously in bloom.
RAPID LEAF MOVEMENT, MICROCLIMATE, AND WATER RELATIONS OF TWO TEMPERATE LEGUMES IN THREE CONTRASTING HABITATS
Authors: Prichard J. M. , Forseth I. N.
Published: January 2018

Diurnal heliotropic leaf movements, microclimate, stomatal conductance and leaf water potential of two leguminous species, Strophostyles helvola and Amphicarpa bracteata, were measured in three different habitats over two growing seasons. The habitats occurred along an environmental gradient from an open, sandy beach to a closed canopy deciduous forest understory. At the beach site, heliotropism in S. helvola resulted in higher irradiances in morning and afternoon hours and lower irradiances during midday periods compared to an horizontal leaf. In an exposed forest site A. bracteata responded within minutes to penetration of the direct solar beam by orienting its leaves to steep angles. In contrast, plants in closed canopy locations showed little diurnal leaf movement. The combined results of leaf energy budget calculations and plant physiological responses suggest that ecological ramifications of these movements vary with habitat. We hypothesize that heliotropism in open habitats increases water use efficiency and maximizes carbon returns on plant investment in photosynthesis. Conversely, we hypothesize that leaf movements in understory habitats represent a morphological mechanism to avoid thermal damage, photoinhibition of the photosynthetic apparatus, and water stress associated with high irradiances.
SEASONAL OCCURRENCE OF XYLEM EMBOLISM IN SUGAR MAPLE (ACER SACCHARUM)
Authors: Sperry John S. , Donnelly John R. , Tyree Melvin T.
Published: January 2018

Xylem embolism, the reduction of water flow by air‐filled vessels, was measured in a stand of 5‐ to 8‐year‐old sugar maple (Acer saccharum Marsh.) saplings growing in a nursery bed in northwestern Vermont. Embolism was quantified as percentage loss in hydraulic conductivity of trunk and branch segments relative to maximum values obtained by removing air from vessels by repeated high pressure (173 kPa) perfusions. Ten segments per tree were cut from 6 trees for each of 11 measurement periods spaced at roughly monthly intervals from May 1986 to June 1987. During the 1986 growing season, embolism increased significantly from 11 to 31% in the larger branches and trunk (segment diameter #8805;0.5 cm), but remained at about 10% in twigs (segment diameter <0.5 cm). This was unexpected because the greatest water stess and thus potential for embolism occurs in twigs. During the winter, embolism increased throughout the trees and the trend with diameter was reversed; by February, small twigs were 84% embolized vs. 69% for larger branches and trunk. Dye perfusions showed that winter embolism in trunks was localized on the south side; this may have resulted from water loss by sublimation or evaporation in the absence of water uptake. Beginning in late March, embolism decreased throughout the trees to approximately 20% in June. This decrease was associated with positive xylem pressure of at least 16 kPa which may have originated in the roots, because weather conditions at the time were unfavorable for the generation of stem pressures characteristic of Acer species in early spring.
GROWTH AND DEVELOPMENT OF REPRODUCTIVE AND VEGETATIVE TISSUES OF BOUGAINVILLEA CULTURED IN VITRO AS A FUNCTION OF CARBOHYDRATE
Authors: Steffen Jody D. , Sachs Roy M. , Hackett Wesley P.
Published: January 2018

Inflorescence meristems and vegetative tissues, excised from noninduced Bougainvillea ‘San Diego Red’ plants, were cultured in vitro in media containing either 3% fructose, glucose or sucrose as carbon sources. Growth and development of young leaves were equivalent whether sucrose or fructose was used whereas floret initiation on inflorescence meristems was much greater when fructose or glucose was the carbon sources. Brief (1‐3 days) exposure of inflorescence meristems to fructose at the beginning of culture and subsequent transfer to sucrose did not increase development over continuous culture in sucrose. Longer exposures (4‐7 days) to fructose with subsequent transfer to sucrose did, however, increase the percentage of meristems developing florets, but such treatment did not increase development to the same level as those exposed to fructose for the entire period in vitro. During the first 18 days of culture, growth of meristems in sucrose was linear while that in fructose was exponential. There was no difference in carbohydrate requirements for floret initiation on meristems excised from short‐day induced or noninduced plants, suggesting that induction does not enhance the ability of meristems to utilize sucrose.
COMPARATIVE POLLEN MORPHOLOGY AND TAXONOMIC AFFINITIES IN CYCADALES
Authors: Dehgan Bijan , Dehgan Nancy B.
Published: January 2018

Scanning and transmission electron microscopy of pollen grains of 29 species, representing the ten extant genera of Cycadales, has provided valuable insight into their relationships. Pollen grains of these taxa are boat‐shaped, monosulcate, and bilaterally symmetrical. They range from narrowly to widely elliptical or subcircular when viewed distally, and have an exine surface of psilate, foveolate, or fossulate. Pollen wall ultrastructure of Cycadales is typically tectate with alveolate∗∗∗spongy exine. The nexine is laminated in all genera. Nexine 1 (footlayer) is present in most species as a thin and often discontinuous layer. There is consistent variation in thickness of the sporoderm layers among the genera but relative uniformity within them. Pollen characteristics are well correlated with macro‐ and micromorphological features, chromosome numbers, geographical distribution, and postulated pollination mode. A close affinity betweenEncephalartos, Lepidozamia,andMacrozamiais recognized. Pollen characteristics of the genusBoweniashow some similarity with those of the latter group. Except for two species ofMacrozamiawhich are narrowly elliptic, all of the genera have widely elliptic pollen and share a psilate exine surface and the thinnest sexine with nearly identical arrangement of alveoli. Pollen grains of the species in the genusDioonexhibit a unique morphology but are more similar toStangeriathan they are to those of taxa in Zamiaceae. The circular outline of the grains and the foveolate exine surface are characters shared by these two genera, but several morphological features distinguishDioonfromStangeria. CeratozamiaandZamiashare a widely elliptic shape, foveolate exine surface and nearly identical sexine, as well as morphological features and chromosome numbers. They differ fromMicrocycasin sexine thickness, gross morphology and chromosome numbers. The pollen grains ofCycas circinalisandC. revolutadiffer in size and structure of the sexine from all other genera and from each other, substantiating their distinct subgeneric delimitations.
ONTOGENETIC DEVELOPMENT OF SPINOUS EXINE IN HIBISCUS SYRIACUS (MALVACEAE)
Authors: Takahashi Masamichi , Kouchi Junko
Published: January 2018

Pollen development in Hibiscus syriacus L. (Malvaceae) was studied with light (LM), scanning (SEM) and transmission (TEM) electron microscopes, with special attention to the formation of extremely long spines of the pollen grains. At the early tetrad stage, probacules are initiated directly on the plasma membrane and grow in coincidence with the height of primexine matrix within a callosic wall. Subsequently, a pretectum appears at the top of the probacules and then a foot layer is formed by accumulation of white line centered lamellations. Before dissolution of the callosic wall, a reticulate patterned pretectum is established around the microspores. There is not, however, any morphological indication on the initiation of the spines during the tetrad period within a callosic wall. It is after dissolution of the callosic wall that the spines of exine begin to form by the apposition of lamellated sheets. The lamellated sheets show a concentric configuration around the developing supratectal spines. The mature pollen grain is spheroidal, polycolporate, 160–170 μm in diameter, with supratectal spines 20–25 μm long. The supratectal spines of Hibiscus pollen are not homologous with the other exinous protrusions which are determined within the callosic wall during tetrad stage.