bluuebunny/crossref_metadata_2025 huggingface dataset:
LEAF ISOZYMES AS GENETIC MARKERS IN DATE PALMS
Authors: Torres Andrew M. , Tisserat Brent
Published: January 2018

The date palm (Phoenix dactylifera L.) is a long‐lived, dioecious, arborescent monocotyledon which must be propagated vegetatively by offshoots to maintain clones. An extensive breeding program begun in 1948 at Indio, California, to obtain superior lines has resulted in the production of several seedling populations of known parents. These were used to study the genetic control of isozymes of alcohol dehydrogenase, esterase, glutamate oxaloacetate transaminase, phosphoglucose isomerase and phosphoglucose mutase from leaf tissue. The five enzyme systems are specified by seven polymorphic genes with 14 alleles. Additional polymorphism was found in two other species of Phoenix. Twenty‐six female and 20 male date palm cvs. were genotyped to provide, insofar as is known, the first single‐gene markers for the date palm and perhaps for any arborescent monocotyledon.
RESPONSE OF BUSH BEAN EXPOSED TO ACID MIST
Authors: Hindawi Ibrahim J. , Rea James A. , Griffis William L.
Published: January 2018

Bush bean plants (Phaseolus vulgaris L. cv. Contender) were treated once a week for six weeks with simulated acid mist at five pH levels ranging from 5.5 to 2.0. Leaf injury developed on plants exposed to acid concentrations below pH 3 and many leaves developed a flecking symptom similar to that caused by ozone. An adaxial, interveinal bleached area resembling SO2 injury also developed on some trifoliate leaves at the low pH treatments. Microscopic observation of injured trifoliates indicated that the palisade cells were plasmolyzed and that the chloroplasts lost structural integrity. Reductions in plant weight and chlorophyll content were detected across the pH gradient. Seed and pod growth were reduced at some intermediate acid depositions even though no visible foliar injury developed. Foliar losses of nitrogen, calcium, magnesium and phosphorous increased with decreases in acid mist pH, whereas foliar potassium concentrations were unaffected by acid mist treatment.
ULTRASTRUCTURE OF DEVELOPING SIEVE ELEMENTS IN THLASPI ARVENSE L. II. MATURATION
Authors: Hoefert Lynn L.
Published: January 2018

Developing sieve elements of pennycress (Thlaspi arvense L.) were studied with the electron microscope. The maturation of sieve elements involved loss of ribosomes from cytoplasm; degeneration of nulcei; modification of endoplasmic reticulum (ER); loss of tonoplast; and disappearance of dictyosomes and dictyosomes vesicles, coated vesicles, microtubules, and microbodies. Such changes produce a mature, presumably conducting cell that contains no nucleus or central vacuole but which retains a thin layer of peripheral cytoplasm with plastids, mitochondria, and smooth ER. Some similar changes have been described in a variety of developing sieve elements of angiosperms, but coated vesicles and microbodies previously have not been followed through sieve‐element maturation. Likewise, few developmental studies have been made of plant sieve elements that exhibit two types of P‐protein, the tubular type and the granular P‐protein body.
THE EXTRAFLORAL NECTARIES OF IPOMOEA LEPTOPHYLLA (CONVOLVULACEAE)
Authors: Keeler Kathleen H.
Published: January 2018

Ipomoea leptophylla Torr. (Convolvulaceae) is a sprawling dry‐site morning glory with two types of extrafloral nectaries: foliar nectaries and nectaries on the outside of the sepals. Both are shown to greatly increase insect visitation to the plant. Ants visiting sepal‐surface nectaries significantly decrease flower damage caused by grasshoppers and seed losses caused by bruchids. These results are similar to those for I. carnea and other plants whose extrafloral nectary‐ant interactions have been studied, but differ in detail. This is the first demonstration of antiherbivore defense of a prairie plant by nectary visitors.
ULTRASTRUCTURE OF STEWARTIOTHECA (MEDULLOSACEAE) PREPOLLEN
Authors: Millay M. A. , Rothwell G. W. , Eggert D. A.
Published: January 2018

Ultrastructure of prepollen from the medullosan seed fern Stewartiotheca warrenae Eggert and Rothwell has been studied with the scanning electron microscope. Nitrocellulose (“liquid” type) peel preparations of pollen organ sections were placed on millipore filters and the grain fragments were extracted by rinsing the peels with acetone. Prepollen is of the Monoletes‐type and is elliptical in polar view, averaging 264 μm long and 183 μm wide. Individual grains possess two deep, crescent‐shaped grooves on the distal surface and a monolete suture with a median deflection proximally. The exine is constructed of a thick (1–2 μm), homogeneous nexine layer overlain by a sexine that is characterized by interconnecting spheroidal chambers. Chamber diameter decreases only slightly from the exterior of the sexine, inward, but the frequency and degree of interconnection among the chambers increases noticeably toward the interior of the wall layer. With regard to this latter feature the prepollen of Stewartiotheca appears intermediate between the organizations known for other Monoletes grains. The grains of Stewartiotheca compare most closely with those of Dolerotheca and Sullitheca.
INTERLOCKED GRAIN, CAMBIAL DOMAINS, ENDOGENOUS RHYTHMS, AND TIME RELATIONS, WITH EMPHASIS ON NYSSA SYLVATICA
Authors: Krawczyszyn J. , Romberger J. A.
Published: January 2018

Interlocked grain in wood of Nyssa sylvatica Marsh. is a lapse‐time record of cyclical changes in inclination (rightward or leftward) of fusiform initial cells in the cambium. Typically the inclination cycles have periods of a decade or more. Such cycles can be interpreted as manifestations of long‐term endogenous rhythms. Interlocked grain in N. sylvatica is not the result of whole‐stem spiral grain that reverses periodically. As wavy grain in other species is a record of wavelike migration of orientational domains along the cambium, interlocked grain in N. sylvatica can be interpreted as being related to a more complex system of domains having long axial dimensions. These domains migrate or change their efficacy and directional sense in place in such a way that some regularity of inclination cycles is maintained at the various stem levels. Inclination cycle lengths have a closer relation to calendar time than they do to the amount of radial growth of the stem. This is affirmed by data from paired stems of similar ages but which grew in diameter at widely different rates.
DNA MICROSPECTROPHOTOMETRY OF SHOOT APICAL MERISTEM CELL POPULATIONS IN CERATOPTERIS THALICTROIDES (FILICALES)
Authors: Polito Vito S.
Published: January 2018

A microspectrophotometric analysis of the DNA content of cell populations in the shoot apical meristem of young and adult stages of the filicalean fern Ceratopteris thalictroides was conducted to determine if the previously reported uptake of labeled DNA precursors by the apical cell was a consequence of endomitotic DNA replication or of DNA synthesis preceeding mitosis. Results demonstrate that in both the young and adult plants the estimated DNA content of the apical cell nuclei parallels that of the other cells of the meristem. There was no evidence of an “apical zone” of endopolyploid cells.
DEVELOPMENTAL ANATOMY AND ULTRASTRUCTURE OF THE ANT‐FOOD BODIES (BECCARIIAN BODIES) OF MACARANGA TRILOBA AND M. HYPOLEUCA (EUPHORBIACEAE)
Authors: Rickson Fred R.
Published: January 2018

Macaranga is a common secondary growth tree of S.E. Asia. Nine species possess hollow stems which harbor an ant colony, and also produce food bodies which are eaten by the ants. In return, the ants protect the plant from herbivore damage. The multicellular food bodies of M. triloba (Bl.) Muell. Arg. are developed on the underside of down‐turned clasping stipules, while in M. hypoleuca (Reichb. f. and Zoll.) Muell. Arg. they are produced on the abaxial surface of young leaves. Food body cells of both species are very rich in lipid, contain large starch grains, and possess an electron‐dense hyaloplasm. It is proposed to name the Macaranga ant‐food bodies Beccariian bodies in honor of the Italian botanist Odoardo Beccari who explored S.E. Asia in the late 1800s.
INVESTIGATIONS OF TERTIARY ANGIOSPERMS: A NEW FLORA INCLUDING EOMIMOSOIDEA PLUMOSA FROM THE OLIGOCENE OF EASTERN TEXAS
Authors: Daghlian Charles P. , Crepet William L. , Delevoryas T.
Published: January 2018

A new fossil flower and inflorescence‐bearing locality has been discovered in the Oligocene of the Texas Gulf Coast. The new flora is similar to the Middle Eocene Claiborne Flora of the southeastern USA, but the quality of preservation is sometimes better in the Oligocene fossils. One component of the new flora, a mimosoid legume inflorescence, appears identical with Eomimosoidea plumosa, first reported from the Claiborne Formation of western Tennessee. Investigations of these younger specimens indicate that the taxon had changed little during the Middle Eocene‐Oligocene interval, and the better quality of preservation of the Texas specimens has provided further insights into the structure of the fossils. Comparisons of the fine structural details of the pollen of Eomimosoidea with similar pollen of extant mimosoids has confirmed that the fossil genus is indeed extinct and suggests that tetrahedral tetrads of columellate, tricolporate pollen grains are ancient, possibly primitive, in the Mimosoideae.
ANT DISPERSAL OF CALATHEA (MARANTACEAE) SEEDS BY CARNIVOROUS PONERINES (FORMICIDAE) IN A TROPICAL RAIN FOREST
Authors: Horvitz C. C. , Beattie A. J.
Published: January 2018

Two tropical herbaceous plant species, Calathea microcephala and Calathea ovandensis, exhibit morphological adaptations for seed dispersal by ants. In the field, 21 ant species are attracted to the arils of the seeds. Previously known as predatory carnivores, the ponerine ants Odontomachus laticeps, O. minutus, Pachycondyla harpax, and P. apicalis carry the seeds toward their nests, behaving as though they were carrying prey. These ants remove the aril in the nest, and seeds without arils germinate more readily than seeds with arils. Ant foraging distances can account for seedling distributions. Myrmecochory may be far more common in tropical rain forests than has been previously suspected.
MORPHOLOGICAL AND ALLOZYMIC EVIDENCE FOR SABATIA FORMOSA (GENTIANACEAE) IN THE SECTION CAMPESTRIA
Authors: Bell Nancy B. , Lester L. James
Published: January 2018

An investigation of eleven populations of Sabatia, utilizing twelve morphological traits and fifteen allozymic loci, revealed the presence of three species in the section Campestria. Currently, the section has two recognized species, S. campestris Nutt. and S. arenicola Greenm. A stepwise discriminant analysis of the morphological data indicated the presence of the third previously described species, S. formosa Buckl. Eight of the loci were either monomorphic or there were no allozyme frequency differences among the three species. An analysis of the allozyme frequencies of the seven polymorphic loci substantiated the presence of S. formosa. Ecological and phenological phenomena further separate the three species. A distribution map of the populations analyzed, populations observed, and populations represented in herbarium specimens indicates that the ranges of the three species are separate although sympatry does occur. Thus, the morphological form described and designated S. formosa by Buckley in 1862 is a separate species.
HETEROPHYLLIC DEVELOPMENT IN MUEHLENBECKIA (POLYGONACEAE)
Authors: Bruck David K. , Kaplan Donald R.
Published: January 2018

Flowering shoots of Muehlenbeckia platyclados Meisn. bear only reduced scale leaves which resemble the membranous sheath portion (ochrea) of leaves of other members of the Polygonaceae. Shoots propagated from cuttings bear enlarged foliage leaves with distinct lamina, petiole, and ochrea zones. The developmental basis for this heterophylly is explored in order to determine whether scale leaves resemble foliage leaves in their pattern of ontogeny or are developmentally unique. SEM and histological analyses have shown that scale leaves and foliage leaves are distinctive from inception. The scale leaf arises as a collarlike growth and extends over the shoot apex as a hooded sheath without evidence of blade initiation. By contrast, the first stage of foliage‐leaf ontogeny is the differentiation of the distal lamina from the future leaf base. As the foliage‐leaf ochrea encircles the stem axis, the lamina grows erect and projects from the abaxial surface of the sheath. Lamina reduction coupled with ochrea elaboration in intermediate leaf types indicate a homology between the entire scale leaf and foliage‐leaf ochrea. Despite this homology, the production of the bladeless scale leaf does not involve a mere suppression of the foliage‐leaf lamina. Erect growth of the saccate ochrea of the foliage leaf contrasts with the hooded expansion of the scale. Early histological differences, including contrasting rates of cell differentiation, also distinguish the two organs. This disparity in modes of growth and differentiation from inception results from separate, predetermined courses of ontogeny. Unlike other plants studied, leaf size and degree of leaf elaboration decrease with shoot meristem enlargement in Muehlenbeckia. Leaf packing does increase with shoot development and may contribute to variations in leaf morphology. It is concluded that the peculiarities of the heterophyllic leaf sequence in Muehlenbeckia are a property of the shoot system as a whole.
MORPHOMETRY OF ORCHID SEEDS. II. NATIVE CALIFORNIA AND RELATED SPECIES OF CALYPSO, CEPHALANTHERA, CORALLORHIZA AND EPIPACTIS
Authors: Arditti J. , Michaud J. D. , Healey P. L.
Published: January 2018

A study ofCalypso, Cephalanthera, CorallorhizaandEpipactisseeds suggests that morphometric analysis can be useful as a taxonomic tool and an indicator of developmental patterns.
ANDROMONOECY IN THE NEW ZEALAND MONTANE SHRUB MANUKA, LEPTOSPERMUM SCOPARIUM (MYRTACEAE)
Authors: Primack Richard B. , Lloyd David G.
Published: January 2018

The ecological and evolutionary advantages of andromonoecy are considered by examining populations of a montane grasslands shrub. Manuka plants (Leptospermum scoparium, Myrtaceae) produce two kinds of flowers: male flowers having functional stamens and a nonfunctional pistil, and hermaphrodite flowers in which both the stamens and pistil are functional. Factors affecting the ratio of the two flower types were investigated at Cass, Canterbury, New Zealand. Stamens mature at the same rate in the two flower types. Individual plants within one population vary from having predominantly hermaphrodite flowers to having no hermaphrodite flowers. Individual variation within a population in the percentage of hermaphrodite flowers is correlated between seasons, indicating some stability in this character. In a particular season, variation among plants within a population in the percentage of hermaphrodite flowers is negatively correlated with date of flowering, but it is not correlated with either the number of flowers or vegetative growth per plant. The hermaphrodite flowers tend to open in the first flush of flowering, and the proportion of hermaphrodite flowers subsequently declines in individual plants and in the population as a whole. The earlier anthesis of hermaphrodite flowers probably increases the frequency of outcrossing; it also provides more time for fruit to mature. The percentage of hermaphrodite flowers is greater toward the top of the plant and among terminal flowers on branchlets than among proximal flowers. The percentage of hermaphrodite flowers on a plant was progressively increased with increasing nutrient treatments. The flowers are visited by a wide range of insects. Fruit set was not increased by hand pollinations of flowers exposed to natural insect visits, indicating that pollinator activity does not limit natural fruit production. A considerable fraction of the variation between individuals in the proportions of male and hermaphrodite flowers is environmentally induced. Andromonoecy may have been selected for in manuka because it is advantageous for pollen to be presented in more flowers than the number of ovule‐ and seed‐bearing flowers. Alternatively, andromonoecy may allow an individual plant to adjust its reproductive output to its immediate physiological condition. However, andromonoecy by itself is not an out‐breeding mechanism.
SPECIES RESPONSE TO A MOISTURE GRADIENT IN CENTRAL ILLINOIS FORESTS
Authors: Adams Dwight E. , Anderson Roger C.
Published: January 2018

Polar and Gaussian ordination applied to data collected from 37 forest sites in central Illinois resulted in a continuous and gradual change in species composition along a moisture gradient. A series of overlapping species success curves formed by plotting Importance Values over stands ordered along the gradient varied continuously in modal location and habitat width. Blackjack oak and black oak dominated upland sandy sites. Black oak, white oak, and shagbark hickory were the most important species on exposed, upper slope positions or ridge tops with silt‐loam soils. Red oak, sugar maple, American elm, and bur oak dominated sheltered locations on lower slope positions and stream terraces. Sycamore, silver maple, and cottonwood were leading tree species in floodplain forests. Conversion of black, white, and red oak forests on silt‐loam sites to sugar maple, white ash, and red elm dominance is evident by high densities of these shade tolerant species in the understory. Composition of forests at the extreme ends of the moisture gradient is more stable than the mesic sites. Maximum tree diversity occurred on mesic sites and decreased toward the extreme ends of the moisture gradient. However, competitive exclusion of shade intolerant species by sugar maple and other species has caused a decrease in understory diversity on mesic sites. Diversity decreased from canopy to understory strata in lowland forests and increased on xeric sites.
LOCALIZATION OF CELL DIVISION ACTIVITY IN THE PRIMARY THICKENING MERISTEM IN ALLIUM CEPA L
Authors: DeMason Darleen A.
Published: January 2018

Stems 1, 2, 3 months old of Allium cepa L. were labelled with tritiated thymidine, fixed in FAA, sectioned, stained with the Feulgen reaction, and prepared for autoradiography. The serial transverse sections were outlined with a camera lucida, recording labelled nuclei as dots. These drawings were used for 3‐dimensional reconstructions of the locations of labelled nuclei. Near the top of the stem, labelled nuclei occur in a broad band, whereas they occur in narrower bands at successively lower levels in the stem, and finally labelled nuclei disappear. The locations of the labelled nuclei correspond to the location of the primary thickening meristem (PTM) in the stem of onion as determined by previous histological and histochemical observations. Microspectrophotometry was used to measure the relative amounts of DNA in Feulgen‐stained nuclei of the PTM in serial transverse sections of 1‐ and 2‐month‐old onion stems. A bimodal distribution was obtained which can be explained by changes in DNA levels during the cell cycle. No evidence of polyploid nuclei was observed. One can conclude, therefore, that the PTM is the site of cell division activity during the primary stem thickening process in onion.
REVISION OF BOLDIA ERYTHROSIPHON HERNDON (RHODOPHYTA, BANGIALES)
Authors: Howard R. Vince , Parker Bruce C.
Published: January 2018

Collection and study of the freshwater red alga, Boldia, from 10 previously unreported habitats disclosed specimens not assignable to either of the two established species. Boldia angustata Deason and Nichols is reduced to synonomy with the earlier described B. erythrosiphon Herndon because of significant overlap between the specific characteristics. Boldia erythrosiphon Herndon emend Howard and Parker is a pleomorphic alga with a more widespread distribution than previously recorded. It is perennial, alternating between an erect saccate frond and prostrate filaments, and both phases are linked by a basal holdfast of pseudoparenchymatous or filamentous construction. Sexual reproduction was not observed; however, asexual reproduction resulted from monospores released by mature fronds, which then germinated to produce basal structures, and through the initiation of erect uniseriate filaments eventually formed new fronds. Absolute growth requirements were not determined; however, similarities in habitats, specifically the abundance of other red algal genera and a predominance of manganese in both snail and rock substrates of Boldia, suggest an interaction of stream temperature, chemistry, substrate, and photoperiod as limiting the distribution of Boldia erythrosiphon.
RADIAL GROWTH IN BEAUCARNEA RECURVATA
Authors: Stevenson Dennis Wm.
Published: January 2018

An essentially unidirectional lateral meristem differentiates in the outer cortex at the hypocotyl‐primary root juncture. This meristem, termed the secondary thickening meristem (STM), then differentiates acropetally towards the shoot apex. It produces secondary tissue (conjunctive tissue) centripetally. Desmogen strands (secondary amphivasal vascular bundles) differentiate from prodesmogen strands in the conjunctive tissue. Root primordia also differentiate from derivatives of this meristem. A primary thickening meristem (PTM) which appears to be continuous with the shoot apex differentiates basipetally. The PTM gives rise to the large primary body of the cortical region of the shoot, and its activity results in the elevation of the leaf bases. In the seedling stages (i.e., for about 2 years) the PTM and STM are longitudinally continuous as a result of the basipetal differentiation of the former and acropetal differentiation of the latter. In adult shoots, however, the two are discontinuous.
SYLLEPTIC BRANCHING IN MYRSINE FLORIDANA (MYRSINACEAE)
Authors: Wheat David
Published: January 2018

Myrsine floridana produces all of its vegetative branches, other than those resulting from pruning or damage, by syllepsis, i.e. by the continuous development of an axillary meristem into a branch without an intervening stage of rest. These sylleptic branches, produced in series, have long and conspicuous hypopodia, broad pith connections with the parent axis, and expanded prophylls. Bud dormancy may be imposed when an axillary meristem is in the axil of the sixth or seventh youngest leaf of the parent shoot. Such axillary meristems may remain at the bud stage with only two pairs of scalelike leaves but these may later give rise to inflorescences or proleptic branches. Proleptic branches lack hypopodia, have narrow piths at their bases, and a series of leaves transitional from the original prophylls to normal foliage leaves within about ten leaves. Myrsine floridana has cortical bundles in the stem, related to the formation of minor lateral leaf traces. The hypopodia of sylleptic branches, since they are leafless, do not have cortical bundles.
ELECTRON MICROSCOPIC OBSERVATIONS ON THE DIFFERENTIATION AND RELEASE OF SPERMATIA IN THE MARINE RED ALGA POLYSIPHONIA HENDRYI (CERAMIALES, RHODOMELACEAE)
Authors: Kugrens Paul
Published: January 2018

Spermatial differentiation in Polysiphonia hendryi begins after nonpolar, avacuolate spermatia are cleaved from their mother cells. The spermatia and their mother cells are embedded within the spermatangium, a confluent wall matrix of the male branch. As the young spermatium enlarges and becomes ellipsoid, the wall fibrils of the spermatangium are compressed, forming a separating layer. Spermatia become polar with rough endoplasmic reticulum coalescing to form a large, fibrillar spermatial vacuole that becomes extracytoplasmic in later development. Following spermatial vacuole formation, dictyosomes form and deposit a spermatial wall, severing the spermatial mother‐cell pit connection. Enlargement of younger spermatia, which are lateral to the older ones, squeezes the maturing spermatia, pushing them from the male branch, and leaving a scar that compresses and heals. Through this release mechanism, new sites are created for additional spermatial proliferation.
ORIENTATION OF THE PLANE OF CELL DIVISION IN FERN GAMETOPHYTES: THE ROLES OF CELL SHAPE AND STRESS
Authors: Miller John H.
Published: January 2018

Apical cells of Onoclea sensibilis L. protonemata were measured to determine areas of new walls which were formed during both transverse and longitudinal cell division. Actual wall areas were compared with calculated areas of hypothetical walls oriented in the opposite sense (i.e., an actual transverse wall compared with a hypothetical longitudinal wall, and the reverse). Among 87 out of 90 cells which were analyzed the actual walls had the least area. Thus, the minimal area hypothesis of cell partitioning accurately predicts wall orientation in this instance, although it appears, on other grounds, that the hypothesis does not furnish a plausible mechanism for wall orientation. The application of Lintilhac's concept of the orientation of cell walls in response to anisotropic stresses in the cell was explored. Photographs of apical cells during deplasmolysis indicated that unequal stresses might be generated in apical cells as a result of the osmotic distension of the elastic protoplast. It is concluded that the primary factor which determines the plane of cell division in the apical cell, and the transition from one‐ to two‐dimensional growth, is the local pattern of stress which exists at the position of the nucleus at the time of onset of cell division and wall formation. Calculations of some geometrical properties of idealized model cells are interpreted to mean that the accuracy of the minimal area hypothesis results from a coincidence of its predictions with predictions of Lintilhac's hypothesis, and no causal significance is attributed to wall areas.
THE EFFECTIVENESS OF FUNGUS GNATS AS POLLINATORS
Authors: Mesler Michael R. , Ackerman James D. , Lu Karen L.
Published: January 2018

Fungus gnats (Sciaridae and Mycetophilidae) are the principal pollinators of Listera cordata (L.) R. Br. (Orchidaceae) and Scoliopus bigelovii Torr. (Liliaceae) in coastal redwood forests of northern California. Although primitive diptera have generally been regarded as relatively inefficient pollinators, fruit set for both species is high: 61–78% for L. cordata (1976–1978) and 94.3–98.5% for S. bigelovii (1978–1979). Since probability of pollination per visit is low, we attribute high fruit set to the large number of gnats present at our study sites and corresponding large number of visits to flowers. The relative frequency of geitonogamous vs. xenogamous pollen flow was estimated by emasculating flowers and subsequently comparing pollen reception or fruit set of emasculates with controls. Results for both species indicate that interplant movement of pollen is common. Thus, fungus gnats can be effective pollen vectors, both in terms of overall fruit set and potential for cross‐pollination.
CAULOCHYTRIUM PROTOSTELIOIDES SP. NOV., A NEW CHYTRID WITH AERIAL SPORANGIA
Authors: Olive Lindsay S.
Published: January 2018

Caulochytrium is a unique genus of chytrids characterized by the production of both sessile zoosporangia and aerial sporangiocarps, the latter unknown in other chytrids. The type species, C. gloeosporii, is an obligate parasite on conidia of the fungus Gloeosporium. The newly described species, C. protostelioides, which was discovered first in the British West Indies and then in North Carolina, is an obligate parasite of the dematiaceous fungus Cladosporium. It differs from the type species in microdimensions, smaller number of zoospores per aerial sporangium, lack of sexuality, production of protostelid‐like sporangiocarps that do not parasitize the host and which float freely on water, and an unrelated host fungus. The family Caulochytriaceae and genus Caulochytrium are emended.
COMPARATIVE POLLEN MORPHOLOGY OF THE MAINLAND AFRICAN GENERA OF MYRISTICACEAE (CEPHALOSPHAERA, COELOCARYON, PYCNANTHUS, AND SCYPHOCEPHALIUM)
Authors: Walker James W. , Walker Audrey G.
Published: January 2018

Pollen of four (Cephalosphaera, Coelocaryon, Pycnanthus, and Scyphocephalium) of the five genera of mainland African Myristicaceae was studied with light, scanning electron, and transmission electron microscopy. Formal generic pollen descriptions are provided for each of these genera. Our study shows that each possesses a distinctive pollen type which is most readily separated from pollen of the other mainland African Myristicaceae on the basis of differences in exine sculpturing and structure. Distinctive palynological features include the reticulate sculpturing with beaded muri of Coelocaryon, the numerous, blunt spines of Pycnanthus, and the minutely “crotonoid” sculpturing pattern of Scyphocephalium. Pollen of Cephalosphaera shows marked resemblances to that of the Madagascan myristicaceous genus Mauloutchia.
ON THE LIFE CYCLE, CYTOLOGY AND TAXONOMY OF CLADOPHORA CALLICOMA FROM INDIA
Authors: Shyam R.
Published: January 2018

The present investigation deals with the cultural observations on the morphology, reproduction, life cycle, cytology and taxonomy of a freshwater Cladophora, C. callicoma (L.) Kütz, from India. There is a regular isomorphic alternation of generations between quadriflagellate zoospore‐producing diploid plants and biflagellate isogamete‐producing haploid plants, coupled with heterothallism in the latter. Chromosome numbers of n = 12 and 2n = 24 were determined respectively for gametophytes and sporophytes. Twelve bivalents were counted in meiosis where chiasmata varied from one to three. In light of above observations, the affinity of C. callicoma with C. glomerata, to which the former has often been assigned, has been discussed. It is proposed that the C. glomerata complex, which consists of intraspecific polyploid races, might have two distinct lines of evolution with regard to life cycle; one with forms having higher ploidy levels and lacking an alternation of generations, and the other with forms having low ploidy levels and alternation of generations.
QUAESTORA AMPLECTA GEN. ET SP. N., A STRUCTURALLY SIMPLE MEDULLOSAN STEM FROM THE UPPER MISSISSIPPIAN OF ARKANSAS
Authors: Mapes Gene , Rothwell Gar W.
Published: January 2018

A well preserved, permineralized seed fern stem is described from the Upper Mississippian Fayetteville Formation of north central Arkansas. Quaestora amplecta gen. et sp. n. is 41.6 cm long and exhibits six pairs of decussate, highly decurrent petiole bases. The stem has a cruciform, exarch protostele with prominent secondary xylem, vascular cambium and secondary phloem. Leaf traces are terete and occur as an outer ring with a small number of internal strands. The cauline vasculature, leaf‐trace production, petiolar anatomy and several other features indicate that this specimen represents the most structurally simple and geologically ancient medullosan stem presently recognized.
NUCLEAR MIGRATION IN GERMINATING SPORES OF ONOCLEA SENSIBILIS: THE PATH AND KINETICS OF MOVEMENT
Authors: Vogelmann Thomas C. , Miller John H.
Published: January 2018

Nuclear migration was observed in individual germinating spores of Onoclea sensibilis from the onset of movement to the completion of mitosis. About 16 hr after the initiation of germination, the nucleus migrated from its initial position in the center of the spore to the proximal side. It then appeared to migrate along the raphe to one end of the spore where an asymmetric division occurred. The average velocity of migration was measured at 0.256 ± 0.065 μm/min. During migration the nucleus underwent changes in shape. No migrations or movement other than that by the nucleus were observed.
A COMPARATIVE STUDY OF CELL DIVISION PATTERNS DURING GERMINATION OF SPORES OF ANEMIA, LYGODIUM AND MOHRIA (SCHIZAEACEAE)
Authors: Raghavan V. , Huckaby Clark S.
Published: January 2018

Cell division patterns during germination of spores of Anemia (A. hirsuta, A. munchii, A. phyllitidis), Lygodium (L. circinatum, L. flexuosum, L. japonicum, L. salicifolium) and Mohria caffrorum have been examined by light microscopy of glycol methacrylate embedded materials. Spores of all species in a genus exhibited a constant pattern of division under different conditions of germination. In spores of species of Anemia, following an asymmetrical division, the proximal cell differentiated into the protonemal cell while the distal cell divided to produce the rhizoid. A similar division sequence was found in spores of Mohria caffrorum, but the fate of cells formed was reversed. In Lygodium spores, a proximal cell formed by an initial division of the spore cut off a protonemal cell, a rhizoid and a wedge‐shaped cell by walls parallel to the polar axis. Our results contradict earlier observations on cell division sequence during germination of spores of these genera based on whole mount preparations.
REPRODUCTIVE CAPACITY AND SEED SIZE IN LUPINUS TEXENSIS
Authors: Schaal Barbara A.
Published: January 2018

The average number of ovules produced per individual of Lupinus texensis is much greater than the average number of seeds per plant. Each plant produces approximately 2,000 ovules but only 2.5% develop into seeds. One fourth of the seeds is lost due to abortion and 0.3% is lost due to predation on the plant. Mature seeds from this population exhibit a five‐fold range in weight, from 10 to 56 mg. The distribution of seed weights in the field population is skewed and leptokurtic. Seed wt is positively correlated with both seed germination and seedling survivorship. Heritability of seed wt is 0.09. There is no correlation between average seed wt per plant and total number of seeds per plant, seeds per pod, or legumes per plant.
SIMULATIONS OF CELL DIMENSIONS IN SHOOT APICAL MERISTEMS: IMPLICATIONS CONCERNING ZONATE APICES
Authors: Niklas Karl J. , Mauseth James D.
Published: January 2018

Surface areas, differential curvatures, volumes, and dimensions of cell‐like units were described for various geometric shapes approaching the morphology of shoot apical meristems (SAM) in vascular plants. Geometric relationships are given in both graphic and dynamic simulations of shape. If the surface of the SAM is described by the revolution of a parabolic, hyperbolic, or circular function, then the greatest change in the surface areas or volumes of equally spaced transverse sections will occur in those regions showing the greatest differential in surface curvature. Subdivision of the SAM volume into cell‐like units leads to quantitative expressions of changes in “cell” length to width and width to depth (aspect) ratios. Dependent upon the geometry of the SAM, differential expressions of aspect ratios may lead to a zonate pattern within the SAM corresponding to a central‐mother‐cell zone (CMC), a peripheral zone (PZ), and a pith‐rib meristem (PRM). The boundary between the PRM and PZ, as seen in median longitudinal section, is a geometric consequence of the deployment of cells with aspect ratios best suited to occupy the entire SAM volume. The number of cell‐like lineages, L, in the SAM may be expressed by the aspect ratio of cells in longitudinal section, nx‐y, such that for the PRM and PZ, L = k1nx‐y‐5.38 and L = k2nx‐y3.18, respectively. Cellular patterns seen in the “corpus” of the SAM may not, therefore, be the a priori result of physiologically distinct populations of cells. Computer simulations are discussed within the data set derived from a study of the SAM of cacti.
NEW BASIC CHROMOSOME NUMBERS FOR GENERA OF NEOTROPICAL FERNS
Authors: Wagner Florence S.
Published: January 2018

Chromosome numbers for eight genera of Costa Rican ferns are reported here for the first time. These are: Neurocallis, n = 58; Marginariopsis, n = 35; Dicranoglossum, n = 36; Glyphotaenium, n = 37; Cochlidium, n = 33; Ormoloma, n = 42; Peltapteris, n = 40; and Loxsomopsis, n = 46. Chromosome observations involving several other genera are included: Solanopteris, n = 37; Xiphopteris, n = 32; Hemidictyum, n = 31: Pleuroderris, 2n = 80; Dictyoxiphium, 2n = 80; and Polystichum, n = 41. These numbers are compared to those of genera of presumed taxonomic affinity.
CASTANEOID INFLORESCENCES FROM THE MIDDLE EOCENE OF TENNESSEE AND THE DIAGNOSTIC VALUE OF POLLEN (AT THE SUBFAMILY LEVEL) IN THE FAGACEAE
Authors: Crepet William L. , Daghlian Charles P.
Published: January 2018

In order to help evaluate the actual affinities of four types of inflorescences that shared gross pollen and inflorescence morphology with the extant Fagaceae, the pollen of the extant Fagaceae was analyzed with light, scanning, and in some cases transmission electron microscopy. The survey illustrates the range in pollen structure in the Fagaceae and confirms that exine ornamentation is a good diagnostic character for determining subfamilies within the modern Fagaceae. Careful comparison of the pollen and floral morphology of the fossils with similar features of the extant Fagaceae revealed only one of these fossil inflorescences was actually fagoid (the other inflorescences will be considered in a subsequent manuscript). The fagaceous inflorescences are catkins conforming in all aspects of pollen, inflorescence, and floret morphology with catkins of the modern subfamily Castaneoideae. The fossil catkins also share the relatively robust inflorescence axis with modern castaneoid inflorescences suggesting that they, too, may have been upright and insect pollinated. The nature of these fossils is consistent with observations that several other families of the “Amentiferae” evolved rapidly during the Upper Cretaceous‐Middle Eocene and this trend suggests that conditions favoring wind pollinated arborescent angiosperm species were optimal during that interval.
THE ORGANIZATION OF THE VASCULAR SYSTEM IN THE STEMS OF THE NYMPHAEACEAE. III. VICTORIA AND EURYALE
Authors: Weidlich W. H.
Published: January 2018

Organization of the stem vascular system was analyzed in Victoria species and Euryale ferox. The stem vascular system consists of a number of concentrically‐organized continuing axial stem bundles. At the node each leaf is supplied with a root trace, two lateral leaf traces, and a median leaf trace. A peduncle fusion bundle is also present at each node. The peduncle fusion bundle supplies vascular tissue to the median leaf trace and to the peduncle trace. Flowers are nonmedian axillary but have specific vascular, spatial, and developmental relationships to leaves in a manner that resembles the genus Nymphaea. On the basis of the analysis of the stem vascular system, Victoria and Euryale are more similar to each other than to Nymphaea. However, the vascular system in Victoria and Euryale is similar enough to Nymphaea to suggest that Nymphaea, Victoria, and Euryale form a natural taxon of unique angiosperms. The organization of the stem vascular system in Victoria and Euryale is dicotyledonous.
ROOT APEX STRUCTURE IN EPHEDRA MONOSPERMA AND EPHEDRA CHILENSIS (EPHEDRACEAE)
Authors: Peterson R. L. , Vermeer Janet
Published: January 2018

The root meristem of E. monosperma and E. chilensis possesses a central group of distinctive, large cells. These cells have large nuclei with scattered heterochromatin, proplastids with no starch, small vacuoles, mitochondria, few dictyosomes and endoplasmic reticulum cisternae, and lipid deposits. Over a 24 hr labelling period, the large cells fail to incorporate 3H‐thymidine, whereas cells both distal and proximal to this region do. A quiescent center which includes these large cells is present therefore. Both species have an extensive root cap, the length being contributed by mitoses in many tiers of cells distal to the quiescent center. The root cap consists of a columella and peripheral regions. Distinctive amyloplasts, an increase in the number of endoplasmic reticulum cisternae and dictyosomes, large vacuoles, and lipid deposits are characteristic of differentiated columella cells. Peripheral cells elongate, lose most of their starch, and are eventually sloughed from the root.
ANTHESIS AND FLORAL SENESCENCE IN CHLOROGALUM POMERIDIANUM (LILIACEAE)
Authors: Jernstedt Judith A.
Published: January 2018

Flowers of the soap‐plant, Chlorogalum pomeridianum (DC.) Kunth., open for a few hours on only one day. The flowers open rapidly in the late afternoon, produce nectar, and close some 6‐8 hr later. As the time of anthesis nears, the tepals become contorted, and progressively larger cavities appear in the tepal mesophyll. Multicellular trichomes at the tips of the tepals increase in length, untangle, and allow the flowers to spring open. Senescence is accompanied by the breakdown of mesophyll cells and by increased ethylene production as the perianth segments twist together and become deliquescent. Anthesis has a weak but discernible rhythmic component and is strongly influenced by alternating light and dark periods. Experiments showed that the length of the uninterrupted light period is of primary importance in the control of anthesis.
LONGITUDINAL MICROFIBRILLAR ALIGNMENT IN THE WALL OF CYLINDRICAL NITELLA RHIZOIDAL CELLS: OBSERVATION UNDER POLARIZING AND INTERFERENCE MICROSCOPES
Authors: Chen James C. W.
Published: January 2018

Polarizing and interference microscopes were employed to measure overall orientation of microfibrils and dry matter (expressed in optical thickness) in the cell wall of Nitella rhizoids. The microfibrils are aligned predominantly parallel to the cell's long axis (positively birefrengent), except in the apical dome where the arrangement appears to be random. The optical thickness, however, is greater at the very tip and the base region. The wall contains about 50‐60% of acid extractable amorphous, noncrystalline substance. This extraction does not make a significant change in the alignment, but the remaining dry matter becomes less at the tip and increases slightly toward the base. The alignment parallel to the direction of cell growth in the rhizoidal cell is different from that of the elongating Nitella internodal cell where the alignment is transverse.
SUBEPIDERMAL AIR SPACES: BASIS FOR THE PHENOTYPIC EXPRESSION OF THE ARGENTEUM MUTANT OF PISUM
Authors: Hoch H. C. , Pratt Charlotte , Marx G. A.
Published: January 2018

The Argenteum (Arg) mutant of pea is characterized by a gray‐green, silvery cast of the leaves and stipules. Light and electron microscopy showed that the nature of the silvery cast was due to extensive intercellular air space between the epidermis and palisade parenchyma. Adaxial epidermal strips from mutant leaves were free of palisade cell wall fragments, whereas similar strips from normal leaves had remnants of the torn palisade cells attached to the epidermal cell walls. The periphery of the epidermal‐palisade cell wall interfaces showed a more electron‐opaque middle lamella in the normal leaves than in the Arg mutant leaves.
THE FLAVONOID CHEMISTRY OF GLANDULARIA BIPINNATIFIDA (VERBENACEAE) AND ALLIED SPECIES
Authors: Umber Ray E.
Published: January 2018

Eight taxa in Verbena have been taxonomically difficult (B. bipinnatifida, V. bipinnatifida var. latilobata, V. Wrightii, V. ciliata, V. ciliata var. longidentata, V. ciliata var. pubera, V. ambrosifolia, and V. ambrosifolia f. eglandulosa). The taxonomic difficulties have been suggested to be the result of widespread hybridization. A flavonoid study of the populations belonging to these eight taxa, combined with a morphological survey resulted in the recognition of four taxa, Glandularia bipinnatifida var. bipinnatifida, G. bipinnatifida var. brevispicata, G. Wrightii, and G. chiricahensis. Hybridization is not responsible for widespread variation in this group.
COMPARATIVE ULTRASTRUCTURE OF VEGETATIVE AND SEXUAL THECAE OF PERIDINIUM LIMBATUM AND PERIDINIUM CINCTUM (DINOPHYCEAE)
Authors: Pfiester Lois A. , Skvarla J. J.
Published: January 2018

Peridinium limbatum(Stokes) Lemmerman reproduces sexually in nitrogen deficient medium. Sexual reproduction is homothallic and similar to that reported for otherPeridiniumspecies. Thecate planozygotes ofP. limbatumandP. cinctumenlarge greatly. Suture bands connecting thecal plates enlarge unequally inP. cinctumproducing a “warty” zygote and equally inP. limbatummaintaining the regular but enlarged appearance of the cell. Zygotes can be recognized by greatly enlarged striated suture bands.
INVESTIGATIONS OF ANGIOSPERMS FROM THE EOCENE OF NORTH AMERICA: RHAMNUS MARGINATUS (RHAMNACEAE) REEXAMINED
Authors: Jones Jay H. , Dilcher David L.
Published: January 2018

Leaf compressions, previously assigned to Rhamnus marginatus Lesquereux, were collected from the Middle Eocene Claiborne Formation of western Kentucky and Tennessee. The leaf architecture and cuticular features of over 40 compressions were carefully examined and compared to those of many extant species of Rhamnaceae and related families as well as fossil specimens previously assigned to this taxon. This leaf type appears to belong to the Rhamnaceae, however, it conforms more closely to species of several genera in the tribe Zizypheae than to those of Rhamnus or other genera in the tribe Rhamneae. Confident assignment to any specific genus within this complex of genera cannot be made on the basis of leaf characteristics alone and would require discovery and analysis of additional vegetative and reproductive organs. Because this fossil leaf form cannot be confidently assigned to any modern genus and earlier classifications appear to be improper, this leaf type has been reassigned to the taxon Berhamniphyllum claibornense gen. et sp. nov. The transfer of this leaf form at the tribe level reaffirms the need for close examination of taxonomic determinations made by early workers.
DIVERSE NODAL ANATOMY OF THE CUNONIACEAE
Authors: Dickison William C.
Published: January 2018

A comprehensive study of nodal anatomy of the Cunoniaceae has revealed an unusually diverse assemblage of nodal types, including patterns with “split‐lateral” traces previously undescribed for dicotyledons. On the basis of leaf arrangement and nodal vascularization, six distinct nodal conditions are recognized in the family. The trilacunar, three‐trace pattern is the ancestral type from which the multilacunar condition evolved by amplification in the number of lateral traces. The “split‐lateral” condition, distinguished by the fusion of lateral leaf traces of adjacent leaves, or the bifurcation of a single trace, and their association with a “common gap,” probably evolved concomitant with the transition from opposite to whorled leaves. The characteristic interpetiolar stipules of the Cunoniaceae are vascularized by veins originating from lateral leaf traces, or by a combination of complete lateral traces and veins arising from lateral leaf traces. Both Aphanopetalum and Bauera possess unilacunar one‐trace nodes. The most satisfactory family placement of both genera remains uncertain, although the unilacunar nodes of Bauera can reasonably be interpreted as a case of reduction from the trilacunar pattern in response to reduced plant size.
A SYNOPSIS OF NORTH AMERICAN ASTERS: THE SUBGENERA, SECTIONS AND SUBSECTIONS OF ASTER AND LASALLEA
Authors: Semple John C. , Brouillet Luc
Published: January 2018

Traditional treatments of Aster were found unsatisfactory in predicting cytological and morphological characteristics of members of various subgenera, sections and subsections of different authors. A realignment of species into these infrageneric categories is presented and is based on sets of shared morphological characteristics of roots or rhizomes, leaves, and phyllaries. Eight subgenera are recognised in Aster. Subgenus Aster is divided into five sections on morphological characteristics: three have X = 9, one has X = 8 and one has X = 7. Subgenus Aster section Dumosi has been redefined and contains all the X = 8 species. Ten X = 5 species and one X = 4 species previously classified in up to six sections of subgenus Aster were found to be morphologically and cytologically related to each other, but unrelated to the other species of Aster. These eleven species have been assigned to the genus Lasallea sensu Semple & Brouillet. Lasallea has been divided in sections and subsections with new combinations presented in this paper.