bluuebunny/crossref_metadata_2025 huggingface dataset:
STIGMA, STYLE, AND OBTURATOR OF SOYBEAN, GLYCINE MAX (L.) MERR. (LEGUMINOSAE) AND THEIR FUNCTION IN THE REPRODUCTIVE PROCESS
Authors: Tilton Varien R. , Wilcox Lee W. , Palmer Reid G. , Albertsen Marc C.
Published: January 2018

Soybeans have a wet stigma overtopped by a pellicle that originates from the cuticle. There are numerous exudate‐filled, axially oriented channels between cells of the transmitting tissue in the stigma and style. Pollen tubes grow in these channels and receive nutrition and mechanical guidance. Transmitting‐tissue cells of the obturator are secretory also, but the obturator in soybean does not appear to control direction of pollen tube growth mechanically. The significant function of transmitting tissue in soybeans is to provide nutrition and to control direction of pollen tube growth.
GERMINATION ECOPHYSIOLOGY OF THE WOODLAND HERB OSMORHIZA LONGISTYLIS (UMBELLIFERAE)
Authors: Baskin Jerry M. , Baskin Carol C.
Published: January 2018

Osmorhiza longistylis is an herbaceous perennial that grows in woodlands of eastern and central North America. In northcentral Kentucky seeds ripen in early to mid July, and dispersal begins in September and October. Although most of the seeds are shed during late autumn and winter, some remain on the dead shoots for up to 18 months. Seeds are dormant at maturity due to an underdeveloped embryo. Embryos grew at low (5 C) temperatures, but only after seeds were given a period of warm (30/15 C) stratification. With an increase in the length of the warm treatment, there was an increase in the number of embryos that grew to full length during a 12‐wk period at 5 C and an increase in the percentage of seeds that germinated. Seeds given 12 wk of warm stratification required more than 8 wk at 5 C to overcome dormancy. Embryos in freshly‐matured seeds averaged 0.60 mm long, but those in seeds given 12 wk warm plus 12 wk cold stratification averaged 8.86 mm. Lengths of embryos of seeds kept moist at 30/15 and 5 C for 24 wk averaged 0.63 and 0.89 mm, respectively. Regardless of age and dispersal time, imbibed seeds must be exposed to high (i.e., summer or autumn) and then to low (i.e., winter) temperatures before they will germinate. Consequently, germination occurs only in spring.
THE FLORAL ECOLOGY OF PLATANTHERA BLEPHARIGLOTTIS
Authors: Cole F. Russell , Firmage David H.
Published: January 2018

The floral ecology of a central Maine population ofPlatanthera blephariglottiswas studied during the 1979–1981 flowering seasons. Although this species possesses characteristics typical of moth‐pollinated plants, only diurnal pollinators were documented, primarily Hesperiidae, Pieridae, and Apidae. Pollinators were scarce throughout the study, yet bagging experiments indicated vectors were necessary for successful capsule set. The average capsule set per plant was lowest (32.2%) in 1979 when 362 plants bloomed and highest in 1980 (80.2%) when 202 plants flowered. Capsule set was found to be limited by pollinator activity. The adaptations ofP. blephariglottis,including sequential flowering, length of receptivity, nectar production and inflorescence size, enable consistently successful reproduction regardless of microhabitat. This species is well‐adapted to reproduce in environments experiencing periods of unfavorable weather and low pollinator abundance.
CLEISTOGAMY IN MICROLAENA POLYNODA (GRAMINEAE): AN EXAMINATION OF SOME MODEL PREDICTIONS
Authors: Schoen Daniel J.
Published: January 2018

A population of the cleistogamous grass, Microlaena polynoda, was investigated to determine some of the factors responsible for adjusting the balance between reproduction by chasmogamous (CH) and cleistogamous (CL) flowers, the tissue costs associated with the two reproductive modes, the fate of progeny produced by each mode, and the genetic diversity of the progeny. Cleistogamous flower production begins earlier in the season than CH flower production. There is a distinct threshold of low light intensity below which mostly CL flowers are produced. Paternal expenditure per plant is an order of magnitude larger for the CH than the CL component. The opposite relation holds for maternal expenditure. Increased maternal expenditure in the CL component may be due to greater fertilization success and retrieval of paternal costs. Cleistogamous seeds are dispersed later than CH seeds. Following dispersal, the spikelet encloses the CL seed but not the CH seed, and is responsible for inducing dormancy. The ratio of seedlings arising from CH seeds to that from CL seeds in a natural habitat is significantly lower than the ratio of estimated numbers of CH to CL seeds produced. There were no detectable polymorphisms among ten presumptive enzyme loci assayed. Many of the features associated with CH and CL reproduction in M. polynoda are in accord with the theoretical requirements for the evolution of closed flower self‐pollination and the maintenance of two distinct methods of reproduction.
ANATOMICAL STUDIES OF CATHAYA (PINACEAE)
Authors: Hu Y. S. , Wang F. H.
Published: January 2018

Cathaya Chun et Kuang is a monotypic genus and one of the gymnosperms endemic to China. We investigated Cathaya argyrophylla with both light and scanning electron microscopy to study the external and internal surfaces of leaf cuticle, leaf blade, petiole, shoot apex, young stem, bark, wood, young and old roots, and mycorrhizae. It is shown that Cathaya has unique characteristics as well as common features of the Pinaceae, there being a difference between Cathaya and Pinus and the rest of the family. So far as the vegetative organs are concerned, the genus is most closely related to Pseudotsuga and Larix.

Data derived from the study of structures of vegetative organs of Cathaya are very different from those of reproductive organs, indicating the complexity of the problem of systematics and evolution in these plants. However, the present study supports the view that Cathaya should not be included in the genus Pseudotsuga as a new species.
A MODEL FOR GRAFT COMPATIBILITY‐INCOMPATIBILITY IN HIGHER PLANTS
Authors: Moore Randy
Published: January 2018

All of the major events comprising the development of compatible and incompatible plant grafts can occur in the absence of direct cellular contact. A model for graft compatibility‐incompatibility is presented which suggests that grafts will be incompatible only if naturally occurring morphogens that promote the formation of a successful graft are overriden by toxins that elicit graft incompatibility. According to this model, a positive recognition system need not be implicated in explaining graft compatibility‐incompatibility in plants.
INITIATION AND DEVELOPMENT OF INFLORESCENCE AND FLOWER IN ANEMOPSIS CALIFORNICA (SAURURACEAE)
Authors: Tucker Shirley C.
Published: January 2018

All flowers of Anemopsis californica, the most specialized taxon of the family Saururaceae, are initiated as individual primordia subtended by previously initiated bracts, in contrast to the common‐primordium initiation of all flowers of Saururus cernuus and of most flowers of Houttuynia cordata. Floral symmetry is bilateral and zygomorphic, and the sequence of initiation among floral parts is paired or whorled. In A. californica, the six stamens arise as three common primordia, each of which later bifurcates to form a pair. The three common primordia occupy sites corresponding to the positions of the three stamens in H. cordata flowers. In Anemopsis, the filaments of each pair are connate. Each stamen pair is vascularized by a single bifurcating vascular bundle. The three carpels per flower are usually initiated simultaneously although there may be some variation. Adnation between stamens and carpels results from zonal growth. Downward extension of the locule, and proliferation and expansion of receptacular tissue and inflorescence cortical tissue around the locule below the bases of the carpels produce the inferior ovary. The inflorescence terminates its activity as a flattened apical residuum, surrounded by bracts subtending reduced flowers most of which have stamens only.
DEVELOPMENTAL STUDIES IN SMILAX (LILIACEAE). I. ORGANOGRAPHY AND THE SHOOT APEX
Authors: Martin Ben F. , Tucker S. C.
Published: January 2018

The ontogeny of the shoot and the tendril‐bearing leaf was studied in four species of Smilax which differ considerably in growth habit. Growth is indeterminate in S. bona‐nox, S. rotundifolia, S. laurifolia and determinate in S. pumila. Shoot apical organization in all four species is consistent with the tunica‐corpus concept. The number of tunica layers varies from 2 in S. bona‐nox, S. pumila, and S. rotundifolia to 3 (2–4) in S. laurifolia. A primary thickening meristem was observed in 5. laurifolia. Shoot tip abortion involving a cessation of vegetative growth resembling that found in many woody plants occurs in S. pumila. Even though there are distinct differences in growth habit, vigor, and anatomy, the four species share many developmental similarities. Hence, subtle changes in apical ontogeny may be associated with marked differences in habit.
SPORE MORPHOLOGY IN THE GENUS BRUCHIA SCHWAEGR. (MUSCI)
Authors: Rushing Ann E.
Published: January 2018

Scanning electron microscopy observations of the spores of Bruchia have resulted in the recognition of four spore types based on the ornamentation of the distal spore surface: warty or verrucate, pitted, reticulate, and spinose. The proximal surface of the spores of all species, except B. brevipes, is characterized by a central aperture region surrounded by a triangular murus or rows of spinae forming a triangle and 1 or 2 smooth or verrucate collars. The ornamentation patterns observed are considered to be characteristic for the genus. Spore morphology alone can rarely be used to distinguish species but in conjunction with certain other characteristics, it is an important taxonomic feature. Spore morphology is a major characteristic used to define the limits of the highly variable species B. flexuosa (spinose spores) and to distinguish it from the closely related species B. texana (reticulate spores). Variations in ornamentation patterns within the genus support the recognition of two subgenera (subgenus Bruchia and subgenus Sporledera). Spore morphology also supports the close relationship between Bruchia and Trematodon and is sufficient to eliminate several questionable taxa from the genus.
STRUCTURAL PATTERN IN ALPINE TUNDRA VEGETATION
Authors: Welden Charles
Published: January 2018

Several aspects of the spatial pattern of plants were investigated in six very different stands in the alpine tundra of the Colorado Front Range. Pattern was related to the internal structure of the stands, to interactions among the species, and to microhabitats within the stands.

Evidence from species‐species associations and species ordinations clearly divided the stands into two groups. The first was characterized by thin, coarse, unstable soils, low plant cover, and nurse‐plant establishment. The second group was characterized by deeper, more mature, and more stable soils, higher plant cover, and more competition between species.

Pattern evidence allowed some species to be categorized as competitors, ruderals, or stress‐tolerators in the context of the alpine vegetation. The two groups of stands also differed in the relative importance of species with these “strategies.”
STRUCTURE AND FUNCTION OF THE GREEN STEM TISSUE IN OCOTILLO (FOUQUIERIA SPLENDENS)
Authors: Nedoff Judith A. , Ting Irwin P. , Lord Elizabeth M.
Published: January 2018

Fouquieria splendens, a desert plant native to the southwestern United States, was studied to determine the capacity for photosynthesis of green stem tissue. The plant is leafless most of the year because of drought, so the capacity for gas exchange by the stems is essential for their photosynthetic function. With secondary growth, sclerified leaf bases which cover the stem become separated, and a transparent cork forms in the furrows between them. A well‐developed chlorenchyma occurs beneath this cork as well as beneath the leaf bases. Chloroplasts of the stem have an unusually high degree of granal stacking, but are mostly typical. Light is transmitted through the leaf base on the young primary shoot and the furrow cork, but not through the older leaf base. Chlorophyll fluorescence studies indicated that the chloroplasts were fully competent and indeed stem tissue is capable of fixing 14CO2 if supplied to cut sections. Despite competent chloroplasts, no exogenous CO2 uptake occurs because the cork is impermeable to CO2, and presumably water. The functional significance of competent chloroplasts in stems that do not transfer gas may be the production of high energy compounds for metabolism, the recycling of internally generated respiratory CO2, or it may simply be a relictual feature in this species of the Fouquieriaceae.
MICROCLIMATIC EFFECTS ON WATER RELATIONS, LEAF TEMPERATURES, AND THE DISTRIBUTION OF HERACLEUM LANATUM AT HIGH ELEVATIONS
Authors: Young Donald R.
Published: January 2018

The small‐scale distribution of an understory herb, Heracleum lanatum, was evaluated in terms of leaf temperature and water relations limitations due to a large leaf size (630 cm2). Diurnal variations in transpiration (4 to 60 mg m−2 s−1) were influenced by fluctuations in solar irradiance, wind speed, leaf temperature and stomatal conductance. Computer simulations indicated that leaf temperatures in a forest clearing would be > 12 C above air temperature, with maximum transpiration rates of 140 mg m−2 s−1, and daily water loss to be over 200% greater than values at natural understory locations. Simulations of nocturnal temperature relations indicated ~100 W m −2 less incident longwave irradiance in the forest clearing as compared to the understory (560 vs. 660 W m−2 at 400 hr). This difference led to predicted leaf temperatures being as low as 6 C below air temperature in the forest clearing while measured leaf temperatures in the forest understory were within 1.5 C of air temperature throughout the night. Furthermore, minimum air temperatures were at or below 6 C on 36% of the nights during the summer growth period indicating that in open areas leaves of H. lanatum would frequently be below 0 C and subject to possible freeze damage. Heracleum lanatum may be more abundant in the shaded understory of the subalpine forest because exposure in open environments would result in high leaf temperatures and increased transpirational water loss during the day, as well as low leaf temperatures with the possibility of freeze damage at night.
A MORPHOMETRIC ANALYSIS OF CYTOLOGICAL CHANGES DURING SPORE MATURATION IN THE MYXOMYCETE DIDYMIUM IRIDIS
Authors: Fagerberg W. R. , Mims C. W.
Published: January 2018

Ultrastructure of spore maturation in the myxomycete Didymium iridis was investigated using morphometric analytical techniques. Changes in actual volume (μm3) and relative volume (Vv) of nuclei, autophagic vacuoles, mitochondria, microbodies, lipid droplets, and spore wall were described for spores in three stages of development. Stage I spores were newly formed, surrounded only by the cell membrane. Stage II spores were approximately 1 hr older than Stage I spores and possessed surface spines, but little if any additional wall material. Stage III spores were 24 hr old and possessed a fully formed, multilayered wall. The results of this study indicate that spore maturation in D. iridis is a multistep process involving a decrease in spore volume and coordinated changes in specific organelle compartments. From Stage I to Stage III, mean spore volume decreased by more than 50%. Percent volume data (Vv) showed that Stage I spores allocated volume equally to all measured organelles except microbodies and the spore wall, the latter of which had not yet begun to develop. By Stage II, only the nucleus and spore wall showed significant changes in Vv values, both increasing. In terms of actual volume, the nucleus, autophagic vacuole and spore wall increased by Stage II. Between Stages II and III the cell wall was the only component to increase in volume, all others decreased in volume. Our data indicate a close relationship between a decrease in organelle volume and an increase in cell wall volume in the Stage III spore. The autophagic vacuole and the cell wall dominated the volume of the Stage III spore while the remaining volume was allocated unequally to the other components.
THE NATURE OF THREADLIKE STRUCTURES AND OTHER MORPHOLOGICAL CHARACTERS IN JACQUESHUBERIA POLLEN (LEGUMINOSAE: CAESALPINIOIDEAE)
Authors: Patel Varsha , Skvarla John J. , Ferguson I. K. , Graham Alan , Raven Peter H.
Published: January 2018

Threadlike structures were observed on many pollen grains of Jacqueshuberia amplifoliola, J. purpurea, and J. quinquangulata of the Leguminosae/Caesalpinioideae. Each end was attached to the highly reticulate polar exine surface of different grains. The consistency of this observation, hence, the absence of free thread ends, is interpreted to mean that they should be considered as either exine bridges or exinial connections rather than viscin threads, although, most likely functionally homologous to viscin threads. Other significant morphological characters were the tricolporate apertures and strikingly lamellate foot layer and endexine.
RELATIONSHIPS OF SEED BANKS TO PLANT DISTRIBUTION PATTERNS IN A FRESHWATER TIDAL WETLAND
Authors: Parker V. T. , Leck M. A.
Published: January 2018

Study of seed banks, field seedling emergence, and survival of macrophytes in four zones (steep bank—SB; gentle bank—GB; midbank—MB; high marsh —HM) along transects perpendicular to a stream channel in a freshwater tidal wetland showed that many species are widely distributed. Of the 35 species in the seed bank, 50% were common to all zones; of the 20 species emerging in the field, 77% were observed in all zones. Density of seeds, seedlings, and mature plants of most species, however, varied significantly with habitat. The seed bank of each zone reflected the dominant vegetation of that zone. Most species, even those with high potential for water dispersal, were not evenly distributed. Reciprocal transplants and survival persistence data of dominants corresponded with their habitat preferences. Seed bank densities differed from zone to zone (SB 1,717 m‐2; GB 1,645; MB 2,730; HM 3,620). In all zones the maximum field seedling density was less than the comparable seed bank one (SB 38% less; GB 33%; MB 46%; and HM 10%). These data, coupled with the higher proportion of the total seed bank and total field seedlings occurring in the HM, suggest that the stream channel sites were more stressful early in the growing season than the HM. Because of differential establishment and survival, importance of a species relative to the rest of the vegetation may change with time and occurrence of a species in the vegetation may greatly outweigh its importance in the seed bank or even the seedling stage. Although seeds of annual species were numerous with seven species making up 85% of the seed bank, annual species comprised only about half of the species recorded in the seed bank of each zone. It is not possible at our present level of understanding of seed banks in the freshwater tidal marsh to predict vegetation change. Various combinations of species attributes contribute to the zonation patterns observed in the freshwater tidal wetland.
PHLOEM ANATOMY OF THE CARBONIFEROUS COENOPTERID FERNS ANACHOROPTERIS AND ANKYROPTERIS
Authors: Smoot Edith L.
Published: January 2018

Phloem histology in the petioles of two genera of Pennsylvanian ferns is detailed from coal balls collected at various localities in North America. Both Ankyropteris and Anachoropteris have primary phloem that completely surrounds the central xylem trace and is separated from it by a parenchymatous sheath. Ankyropteris contains very narrow (about 13.5 μm diam) sieve elements and a few strands of phloem parenchyma. End walls are either horizontal or slightly oblique and sieve areas as well as scattered individual pores have been observed. Anachoropteris phloem contains two different sizes of sieve elements. Small sieve elements that surround the C‐shaped trace are similar to those seen in Ankyropteris. Larger elements (approximately 50–120 μm in diam) are present only within the C‐shaped trace, and are elongate (up to 2.5 mm) with very oblique end walls. Sieve areas on these large cells are conspicuous, 5–8.5 μm in diam and aggregated into groups. The cell wall within each sieve area appears to be composed of criss‐crossed fibrillar material. Phloem anatomy in these two ferns is compared to that previously described in other Carboniferous vascular cryptogams, as well as that known from extant plants.
ANATOMY OF IMMATURE GRAINS OF EIGHT MATERNAL EFFECT SHRUNKEN ENDOSPERM BARLEY MUTANTS
Authors: Felker Frederick C. , Peterson David M. , Nelson Oliver E.
Published: January 2018

The anatomical basis for the shrunken endosperm phenotype of eight recessive maternal effect mutants (seg1‐seg8) of barley (Hordeum vulgare L.) is described. Plants which are homozygous recessive for these nuclear genes produce only shrunken seeds regardless of pollen source. Light microscopy revealed that four of the mutants, seg1, seg3, seg6, and seg7, exhibited premature termination of grain filling because of the necrosis and crushing of the chalaza and nucellar projection of the pericarp early in the grain‐filling period, resulting in thin, wrinkled seed. Endosperm growth of these mutants before the occurrence of chalazal necrosis seemed normal. The other four mutants exhibited characteristic abnormalities in the endosperm growth pattern but normal development of matemal‐origin tissues. Endosperm size was severely reduced in seg2, in which two flat columns of tissue were present with no central endosperm. Seg4 and seg5 developed distorted, disorganized endosperms of variable size. Endosperms of seg8 developed as two well‐filled lobes with no central endosperm, resulting in a distinct dorsal crease. We suggest that the mutants are useful as probes to study maternal effects on endosperm development.
THE HYBRID ORIGIN OF ASTER ASCENDENS (ASTERACEAE)
Authors: Allen Geraldine A.
Published: January 2018

Aster ascendens Lindl. is a rhizomatous perennial of the Great Basin region of the western United States, with a chromosome base number of x = 13. Populations in the southern and western parts of the range are mainly diploid (n = 13) and those in the north and east are mainly tetraploid (n = 26). This species is postulated to be an amphiploid which has resulted from hybridization between the western Cordilleran A. occidentalis (T. & G.) Hook, and the Great Plains species A. falcatus Lindl. Aster ascendens is intermediate between these two species in most morphological traits, but resembles A. occidentalis in ray color and general growth habit, and A. falcatus in the shape of the outer phyllaries. The karyotype of A. ascendens also exhibits a combination of the features found in A. occidentalis and A. falcatus karyotypes. Of the specimens collected for this study, 13% were putative backcrosses of A. ascendens to one of its parent taxa or to a closely related species; this suggests that there is potentially continuing genetic interchange between the species groups that gave rise to A. ascendens.
SEX DIFFERENTIAL FLORAL LONGEVITY, NECTAR SECRETION, AND POLLINATOR FORAGING IN A PROTANDROUS SPECIES
Authors: Devlin B. , Stephenson A. G.
Published: January 2018

Sex differential nectar production, floral longevity and pollinator foraging were examined in Lobelia cardinalis, a self‐compatible, protandrous species that is hummingbird pollinated. The staminate phase of the flowers lasts significantly longer and produces significantly more nectar (total sugar) per day than the pistillate phase of the flowers. Additional pollen is presented throughout the staminate phase.

Because inflorescences of L. cardinalis mature acropetally, the nectar reward on any given day is greatest at the top of the inflorescence (where staminate phase flowers are located). Hummingbirds appear to be sensitive to this pattern of nectar presentation as they most commonly began foraging in the middle of an inflorescence and proceeded upward. This foraging pattern tends to promote outcrossing and suggests that staminate phase flowers are visited more often than pistillate phase flowers. We conclude that L. cardinalis emphasizes the male function at anthesis. Others have hypothesized that the features of this species are a logical consequence of intrasexual selection, but further research is needed before we place great confidence in a sexual selection interpretation of our data.
RESPONSE OF THE ANNUAL ABUTILON THEOPHRASTI MEDIC. (MALVACEAE) TO TIMING OF NUTRIENT AVAILABILITY
Authors: Benner B. L. , Bazzaz F. A.
Published: January 2018

Because resource variability is likely to be high in disturbed environments, colonizing species should be opportunistic in their abilities to use resources at any time during the growing season. We examined the effects of timing of nutrient availability on seed quantity and quality in the colonizing annual Abutilon theophrasti. Plants were grown under six different nutrient treatments involving additions of different size, frequency and timing but having the same total amount of nutrients in all treatments. The plants showed an opportunistic response, being able to use nutrients supplied at different times for reproduction. However, when nutrient availability was delayed until fruit maturation had begun, seed number and total seed weight were reduced, production of mature fruits was delayed, and seed P concentrations were reduced. Seeds from the first two fruits of the plants had higher N concentration (mg/g), higher N content (mg/seed), lower P concentration, higher K content, and higher mean seed weight.
THE FATE OF THE DWARF SHOOT APEX IN BRISTLECONE PINE (PINUS LONGAEVA)
Authors: Ewers Frank W. , Schmid Rudolf
Published: January 2018

The fate of the pine dwarf shoot (DS) apex after needle initiation has been controversial. Dwarf shoot primordia of Pinus longaeva were examined to determine the developmental basis for DS with and without interfoliar buds. Interfoliar buds are microscopic buds derived from the original terminal apex of the DS. In October, all the DS primordia are similar in size and appearance. However, as the needles elongate in the following June the apices of more proximal DS decrease in size, such that by July there is a clear diminishing size gradient of apical domes in going from the most distal to the most proximal positions. The distal DSs start to form bud scales in July and have fully formed interfoliar buds by mid‐August. In contrast, those DS apices lacking protective bud scales at needle maturity become suberized and can never proliferate into long shoots. The distal placement of interfoliar buds may be due to a group effect, where each developing DS inhibits the more proximal DSs in the long shoot terminal bud.
VEGETATIVE REGROWTH FOLLOWING CUTTING IN THE SHRUB BACCHARIS PILULARIS SSP. CONSANGUINEA (DC) C. B. WOLF
Authors: Hobbs Richard J. , Mooney H. A.
Published: January 2018

The resprouting ability following cutting of the chaparral shrub Baccharis pilularis ssp. consanguinea (DC) C. B. Wolf was investigated following the felling of individuals of various ages. Numbers of resprouts and resprout biomass were low in 1‐yr‐old shrubs, increased to a maximum in shrubs 3–4 yr old, and declined to zero in shrubs <8 yr old. Numbers of leaves produced were also lower in 1‐yr‐old shrubs. The results are interpreted on the basis of the internal origin of resprout buds and the increasing extent of the shrub's root system as it matures.
PITYOSTROBUS PUBESCENS, A NEW SPECIES OF PINACEOUS CONES FROM THE LATE CRETACEOUS OF NEW JERSEY
Authors: Miller Charles N.
Published: January 2018

This new species is based on a single semifusinized cone from the Late Cretaceous (Cenomanian) of New Jersey. The cone is flattened but essentially complete. It is 55 mm long and 8 by 13 mm in diam. Scale apices are thin, rounded, and entire, lacking evidence of an umbo or spine. The vascular cylinder of the cone axis is organized as a series of separate strands. The scale is made up of a basal portion that stands out nearly perpendicular to the cone axis and a sharply upturned distal portion. The bract base has a pronounced abaxial keel. Bract and scale traces diverge from the vascular cylinder of the cone axis separately from one another. A poorly developed interseminal ridge is present at the chalazal end of the seeds. An unusual feature of the cone is the presence of a trichome‐bearing epidermis on the cone axis, bract‐scale complex, and near the scale apex. Resin canals diverge into the bract‐scale complex abaxial to the scale trace with branches becoming adaxial to the scale trace outward. A number of features of the new species occur in cones of Abies, Cedrus, Keteleeria, Larix, Picea, Pseudolarix, Pseudotsuga, and Tsuga as well as in the extinct genus Pseudoaraucaria. Features of Pinus are absent. This suggests that Pseudoaraucaria may have served as an ancestral source for modern genera other than Pinus with Pityostrobus pubescens representing an evolutionary intermediate.
AERODYNAMICS OF WIND POLLINATION IN SIMMONDSIA CHINENSIS (LINK) SCHNEIDER
Authors: Niklas Karl J. , Buchmann Stephen L.
Published: January 2018

Wind tunnel analyses of Simmondsia chinensis (Link) Schneider or “jojoba” were conducted to quantify the behavior of airborne pollen grains around individual branches and leaves and near individual carpellate flowers. Field data (wind velocity) were used to ensure a correspondence between wind tunnel and natural conditions. Based upon the visualization of individual pollen grain trajectories, it is concluded that pollen deposition on stigmatic surfaces is influenced by large‐scale aerodynamic patterns, generated by foliage leaves, and small‐scale airflow patterns, formed around and by floral parts and stigmas. Leaves are seen to deflect airborne pollen grains into trajectories that can intersect ambient airflow at 90° angles, showering decumbent carpellate flowers with pollen. Similarly, flowers can deflect pollen upward and downwind, toward other flowers. The extent of floral bract and sepal recurvature is shown to influence the extent of pollen deposition by determining the characteristic airflow pattern around stigmas.

Available evidence concerning the relatively recent evolutionary transition to anemophily in Simmondsia is interpreted within the context of morphological adaptations and exaptations favoring wind pollination.
MINERAL CONCENTRATIONS IN AN AUTOPARASITIC PHORADENDRON CALIFORNICUM GROWING ON A PARASITIC P. CALIFORNICUM AND ITS HOST, CERCIDIUM FLORIDUM
Authors: Ehleringer James R. , Schulze E.‐D.
Published: January 2018

Tissue concentrations of 12 mineral elements (Al, Ca, Cu, Fe, K, Mg, Mn, amino‐N, Na, P, Si, and Zn) were measured in an autoparasitic mistletoe (Phoradendron californicum), the parasitic mistletoe on which it was growing (Phoradendron californicum), and the host tree (Cercidium floridum). Mineral concentrations in the autoparasite were typically 1.1–1.3 times higher than in the parasite. Mineral concentrations of all elements except Ca, Fe, Mg, Mn, and Si were higher in the parasitic mistletoe than its host. Mineral concentration differences are discussed relative to accumulation via the transpiration stream and translocation within the host via the phloem.
STUDIES OF PALEOZOIC MARATTIALEANS: NEW SPECIES OF SCOLECOPTERIS (MARATTIALES) FROM THE PENNSYLVANIAN OF NORTH AMERICA
Authors: Lesnikowska A. D. , Millay M. A.
Published: January 2018

Two new species of the late Paleozoic fern Scolecopteris (Marattiales) are described and their relationships within the genus are discussed. Scolecopteris charma sp.n., from Steubenville, Ohio (Duquesne Coal, Upper Pennsylvanian), is similar to species in the Oliveri group, while S. gnoma sp.n. from Providence, Kentucky (Baker Coal, Middle Pennsylvanian), compares favorably with the Latifolia species group. Scolecopteris gnoma is most similar to S. fragilis but differs in its smaller synangia and spore type. S. charma appears generally similar to S. iowensis because of its large pedicel and histologically undifferentiated walls, but differs in a number of characters such as vasculature and spore type. Despite its occurrence late in the Pennsylvanian, S. charma is thought to possess a number of primitive character states (large trilete spores, vascularized pedicels, flat pinnules with downturned margins). Using the same criteria for the much older S. gnoma, we note a number of relatively apomorphic character states (small monolete spores, unvascularized pedicels, extended pinnule margins). An outgroup analysis of species‐level characters of Scolecopteris gives a better concept of primitive versus derived traits in marattialean and other ferns. Genera in the Paleozoic fern orders Filicales (Ankyropteris) and Zygopteridales (Corynepteris, Musatea) were chosen as outgroups, and the comparisons support suggestions for the polarity of several important characters. Some of these agree with previously proposed evolutionary polarities based on the geological occurrence of marattialean ferns.
ULTRASTRUCTURAL CHANGES IN SUNFLOWER CHLOROPLASTS FOLLOWING INOCULATION WITH PSEUDOMONAS SYRINGAE PV. TAGETIS
Authors: Freeman Thomas P. , Duysen Murray E. , Gulya Thomas J.
Published: January 2018

Severe chlorosis and ultrastructural modifications of chloroplasts occur in sunflower in response to infection by Pseudomonas syringae pv. tagetis. Chlorosis became apparent within 2 days after the cotyledons of 10‐day‐old sunflower seedlings were inoculated with the bacteria. The first symptoms generally appeared in the center of leaves at the second node above the cotyledons. Leaves above the second node lost essentially all of their pigmentation but remained turgid and continued to expand. Grana thylakoids became dilated and separated from the granal stacks. These thylakoid membranes did not chemically breakdown as in the case in chromoplast formation or normal chloroplast senescence. Both grana and stroma thylakoid membranes coalesced to form a large membrane sheet within the plastid. The ultrastructural changes are unlike those reported to be caused by other chlorosis‐inducing bacteria or chlorosis associated with normal senescence.
COMPARATIVE ELECTROPHORETIC STUDIES OF CARDUUS PYCNOCEPHALUS L., C. TENUIFLORUS CURT. (ASTERACEAE), AND THEIR HYBRIDS
Authors: Olivieri Isabelle
Published: January 2018

Electrophoretic studies on Carduus pycnocephalus L., C. tenuiflorus Curt., and their hybrids, showed that, although hybridization is common, the two parental species are quite well separated by their enzymatic patterns. This was confirmed by data on fertilization and achene abortion rates of the intermediate forms between the two species. The seed set of hybrids was the lowest in California, where the two species have been introduced.
INHIBITION OF GRAVITROPISM IN PRIMARY ROOTS OF ZEA MAYS BY CHLORAMPHENICOL
Authors: Moore Randy
Published: January 2018

Primary roots of Zea mays seedlings germinated and grown in 0.1 mm chloramphenicol (CMP) were significantly less graviresponsive than primary roots of seedlings germinated and grown in distilled water. Elongation rates of roots treated with CMP were significantly greater than those grown in distilled water. Caps of control and CMP‐treated roots possessed extensive columella tissues comprised of cells containing numerous sedimented amyloplasts. These results indicate that the reduced graviresponsiveness of CMP‐treated roots is not due to reduced rates of elongation, the absence of the presumed gravireceptors (i.e., amyloplasts in columella cells), or reduced amounts of columella tissue. These results are consistent with CMP altering the production and/or transport of effectors that mediate gravitropism.
POLLINATION AND SEED SET IN DIERVILLA LONICERA (CAPRIFOLIACEAE): TEMPORAL PATTERNS OF FLOWER AND OVULE DEPLOYMENT
Authors: Thomson James D.
Published: January 2018

Ovule development in Diervilla lonicera (Caprifoliaceae) is limited by insufficient pollination early in the blooming period and during extensive rainy periods. Production of flowers is skewed in time; an initial burst of flowering is followed by a long period of sparse flower production. Ovule number per flower increases through the blooming period. I discuss the interactions of fruit and seed set, ovule number, and bumble bee pollinator visitation patterns. When certain flowers have a higher a priori probability of successful pollination, it may be advantageous for plants to put more ovules in those flowers. Selective ovule deployment may be a general adaptive phenomenon that has received little attention.
ULTRACYTOCHEMICAL LOCALIZATION OF PLASMA MEMBRANE‐ASSOCIATED PHOSPHATASE ACTIVITY IN DEVELOPING TOBACCO SEEDS
Authors: Mogensen H. Lloyd
Published: January 2018

Plasma membrane‐associated phosphatase activity was found in integumentary cells of developing tobacco ovules from the megaspore tetrad stage to seed maturity. Enzyme activity is greatest in the innermost layers of the integument from the mature megagametophyte stage on. The egg, zygote, and synergids almost totally lack plasma membrane‐associated reaction product, while the antipodals show some activity at their chalazal ends. The endosperm has much plasma membrane‐associated phosphatase activity in most of its cells during development, but it is primarily the outermost plasma membranes of the surface cells of the embryo that have associated reaction product. It is concluded that the plasma membrane‐associated phosphatase activity is related to active transport of assimilates and that the integument is the most important site of active transport in the young ovule. After fertilization, in addition to the innermost layers of the integument, the endosperm and the outermost cells of the embryo become involved in active transport, which continues to seed maturity.
THE DELIMITATION OF BIGNONIACEAE AND SCROPHULARIACEAE BASED ON FLORAL ANATOMY, AND THE PLACEMENT OF PROBLEM GENERA
Authors: Armstrong Joseph E.
Published: January 2018

The delimitation of Bignoniaceae and Scrophulariaceae has long been a taxonomic problem. Several genera, including Paulownia, Schlegelia, Gibsoniothamnus, and Synapsis, have been variously placed in one or the other family. Differences between these two families have been noted with regard to the presence of endosperm, embryo and seed morphology, and placentation; however, the lack of comprehensive data on the distribution of such characters within these two families left the delimitation problem unsolved. A comprehensive study of floral anatomy confirmed a basic difference in the placentation of these two families, as well as a basic difference in gynoecial vascularization. Paulownia has a floral anatomy, embryo morphology, and seed morphology consistent with placement in Scrophulariaceae. While reminiscent of Bignoniaceae, Paulownia is not an intermediate genus linking the two families. Schlegelia and Gibsoniothamnus have a floral anatomy consistent with placement in Scrophulariaceae. Schlegelia also has a scrophulariaceous seed morphology. Considered anomalous in the Bignoniaceae, the Schlegelieae similarly are distinct in the Scrophulariaceae.
GENOMICALLY BASED GENERA IN THE PERENNIAL TRITICEAE OF NORTH AMERICA: IDENTIFICATION AND MEMBERSHIP
Authors: Barkworth Mary E. , Dewey Douglas R.
Published: January 2018

Dewey and Löve have suggested that generic limits in the Triticeae should be determined by the genomic data, taxa with different genomic constitutions being placed in different genera. According to this interpretation, nine genera of perennial Triticeae occur in North America. Five of these (Critesion, Elymus, Leymus, Pascopyrum, and Pseudoroegneria) include species native to North America; the other four (Agropyron, Elytrigia, Psathyrostachys, and Thinopyrum) are represented only by introduced species. Four hybrid genera of perennial Triticeae also occur in North America, × Elyleymus, × Pseudelymus, × Leytesion, and × Elytesion, the last being a new generic hybrid name necessitated by the treatment presented here. The number of naturally occurring intergeneric hybrids in North America is 18 according to this treatment whereas Bowden, using more traditional generic treatments, recognized 22 such hybrids in North America.

For nonhybrid genera, an identification key and a brief description are provided, together with a table showing the taxa included in each genus. For hybrid genera, the species are merely listed. Several new combinations, mostly of hybrid taxa, are presented in order to accommodate the revised generic treatment.
A NEW NITROGEN‐FIXING CYANOPHYTE‐HEPATIC ASSOCIATION: NOSTOC AND PORELLA
Authors: Dalton David A. , Chatfield J. Mark
Published: January 2018

Porella navicularis, a common leafy liverwort in western North America, was found to possess numerous epiphytic Nostoc colonies. Although the abundance of colonies was variable, the association was found consistently throughout a broad geographic range. Unlike cyanobacteria in other hepatic assocations, the Nostoc occurred as distinct colonies harbored in crevices and curled margins of leaves. Heterocyst frequency was 3–7%. Acetylene reduction activity was present in 85% of samples examined, with an average value of 53.5 nmol C2H4∙g dry wt‐1∙hr‐1 and a maximum of 316 nmol C2H4∙g dry wt‐1∙hr‐1. This suggests that bryophyte nitrogen‐fixing associations may be more important than previously realized.
PLOIDAL CHANGES IN CLONAL CULTURES OF SPIROGYRA COMMUNIS AND IMPLICATIONS FOR SPECIES DEFINITION
Authors: Hoshaw Robert W. , Wang Jen‐Chyong , McCourt Richard M. , Hull Herbert M.
Published: January 2018

A clonal culture of Spirogyra filaments of initially uniform width produced filaments of three additional significantly different widths. Group I filaments of the original clone were 30.9 ± 0.7 μm wide (mean ± SD, N = 50). Group I filaments produced Group II filaments (22.0 ± 1.1 μm) through vegetative growth and sexual reproduction. Zygospores from homothallic Group I filaments produced germlings representative of Groups I and II; zygospores from homothallic Group II filaments produced germlings representative of Group II only. Germlings of Groups III (27.7 ± 1.0 μm) and IV (44.9 ± 0.8 μm) were produced in the cross of I × II. Viable zygospores from homothallic Group III filaments were obtained. Cells of Group IV filaments were initially binucleate and did not conjugate. Of the six intergroup crosses possible, four resulted in conjugation‐tube formation only; two crosses yielded zygospores (I × II and III × IV). Germlings from the successful cross of Groups III and IV produced filaments of all four groups. Chromosome counts were: Group I (24), Group II (12), Group III (18), and Group IV (24, one nucleus). Relative nuclear fluorescence values of mithramycin‐stained DNA were (mean ± SD, N ≥ 30): Group I (11.1 ± 1.4), Group II (5.7 ± 0.7), Group III (8.8 ± 1.3), and Group IV (10.0 ± 0.9, one nucleus). Cytologically, Group II appears to be a diploid (2x), Group I a tetraploid (4x), and Group III a triploid (3x). Systematically, Groups I, II, and III key out to Spirogyra singularis, S. communis, and S. fragilis, respectively, using Transeau's mongraph of the family Zygnemataceae. These species are interpreted to represent a species complex of S. communis (whose name has priority) with the ancestral haploid (x = 6) missing.
VARIATION IN THE POLLINARIA, ANTHERS, AND ALAR FISSURES OF COMMON MILKWEED (ASCLEPIAS SYRIACA L.)
Authors: Morse Douglass H. , Fritz Robert S.
Published: January 2018

We measured 10 characters of pollinaria, anthers, and alar fissures from the flowers of seven clones of common milkweed Asclepias syriaca L. to test whether significant differences existed among them. Strong among‐clone differences existed for most of these characters. However, these differences were not correlated with each other, except for width of the alar fissure and width of the translator arm. Thus, these floral structures vary mostly in shape, rather than size per se. Few correlations among characters occurred at a within‐clone level. Clones growing in the open and shade differed in half of the characters measured, but habitat did not substantially change the among‐clone size patterns observed. The alar fissure–translator arm relationship might promote differential uptake of pollinia; however, A. syriaca does not exhibit a clear separation into donor and recipient clones.
POLLEN MORPHOLOGY AND THE RELATIONSHIPS OF AËTOXYLON, AMYXA, AND GONYSTYLUS TO THE THYMELAEACEAE
Authors: Nowicke Joan W. , Patel Varsha , Skvarla John J.
Published: January 2018

The pollen of three closely related genera, Aëtoxylon, Amyxa, and Gonystylus is compared in SEM and TEM with that of Thymelaeaceae, s. s. The Thymelaeaceae have spherical, pantoporate grains with a crotonoid tectum in which the basic subunit is triangular in shape and forms a continuous triangular array. Thin section (TEM) and fractures (SEM) revealed that these subunits are attached to a ringlike network of horizontal rods. Within the Thymelaeaceae, the triangular subunits vary in the number of subdivisions and degree of fusion and form a morphological continuum. Aëtoxylon, Amyxa, and Gonystylus also have spherical, pantoporate pollen but with a tectum in which almost all of the distinction of the subunits appears to have been lost. The structure of the exine in Aëtoxylon, Amyxa, and Gonystylus, however, is unique thus far within the angiosperms. Thin section revealed a thick tectum with a layer of short or even granular columellae, then a thin, discontinuous layer from which larger columellae appear to hang. There is no evidence of an endexine even in the region of the apertures. The distinctive exine structure would support the treatment of Aëtoxylon, Amyxa, and Gonystylus as a separate family, Gonystylaceae, allied to the Thymelaeaceae.
STEM ELONGATION OF XANTHIUM PLANTS PRESENTED IN TERMS OF RELATIVE ELEMENTAL RATES
Authors: Maksymowych Roman , Maksymowych Andrew B. , Orkwiszewski Joseph A. J.
Published: January 2018

Vegetative Xanthium plants grown under noninductive conditions were marked along the stem with India ink and photographed during three successive days. The relative elemental rates of stem elongation [d(dX/dt)/dX] were estimated for 18 plants between 15 and 18 plastochrons. On the average, only the 8.0 cm terminal part of the stem was elongating in this group of plants. Young internodes were elongating at constant relative elemental rates ([d(dX/dt)/dX] was about 0.2 days–1); nodal portions of the stem beteween two young internodes were not elongating. Internodes longer than 2 cm displayed an acropetal pattern of elongation in which the basal part of an internode stopped elongating and matured first and the apical portion last. The pattern of elongation of the stem could be best approximated to a set of cascading waterfalls with declining plateaus in the direction of the water flow. The acropetal pattern of individual internode elongation observed in Xanthium was similar to those reported for Helianthus and Phaseolus internode growth.
ULTRASTRUCTURAL ASPECTS OF CHILLING INJURY IN THE SOYBEAN SEED RADICLE
Authors: Chabot Jean Fincher , Leopold A. Carl
Published: January 2018

Imbibitional chilling injury of soybean seeds was studied using light and electron microscopy. Intact seeds were allowed to take up water at 4 C or room temperatures and the ultrastructure of the radicle was examined after hydration. In chilled seeds, mitochondria showed weakly defined envelopes and cristae, in contrast to the well‐formed internal structure in the controls. Nuclei of chilled seeds were irregular in shape. Tannic acid was used as a probe of plasmalemma integrity. Most cells in both chilled and control treatments were able to exclude tannin, indicating that chilling injury effects did not damage the plasma membrane enough to allow passage of molecules of that size.