bluuebunny/crossref_metadata_2025 huggingface dataset:
COMPARATIVE STUDIES OF THE NODAL AND VASCULAR ANATOMY IN THE NEOTROPICAL CYATHEACEAE. III. NODAL AND PETIOLE PATTERNS; SUMMARY AND CONCLUSIONS
Authors: Lucansky Terry W. , White Richard A.
Published: January 2018

Comparative studies of the nodal and vascular anatomy in the Cyatheaceae are discussed as they relate to the taxonomy and phylogeny of the family. There is in the Cyatheaceae (excluding Metaxya and Lophosoria) a basic nodal pattern consisting of four major phases of leaf trace separations. Abaxial traces arise from the leaf gap margins, and the last abaxial traces from each side of the gap are larger and undergo numerous divisions. Distally adaxial traces separate from the gap margins, and the last adaxial traces are usually larger and undergo multiple divisions. In addition, medullary bundles frequently become petiole strands of the adaxial arc in the petiole. Rarely, cortical bundles form petiole strands in the abaxial arc in the petiole. Leaf gaps of the squamate genera of the Cyatheaceae are fusiform and possess prominent lateral constrictions which result from medullary bundle fusions and the separation of leaf traces. A characteristic petiole pattern is found in all members of the Cyatheaceae. There is an increase in the complexity of the petiole vascular tissue which results in a gradation from the undivided strand in Metaxya, to the three‐parted petiole pattern in Lophosoria, and finally to the much‐dissected petiole vascular tissue in the advanced genera. Nodal and vascular anatomy data basically support Tryon's phyletic scheme for the family. The Sphaeropteris‐Alsophila‐Nephelea line shows certain tendencies toward increased complexity of nodal and vascular anatomy, whereas the Trichipteris‐Cyathea‐Cnemidaria line shows the same anatomical and morphological characters in a direction of increased simplification or reduction.
MORPHOLOGY, SEASONAL VARIATION, AND FUNCTION OF RESIN GLANDS ON BUDS AND LEAVES OF POPULUS DELTOIDES (SALICACEAE)
Authors: Curtis John D. , Lersten Nels R.
Published: January 2018

When buds form in summer or early fall, modified stipules act as bud scales and their adaxial epidermis secretes a resin that fills the bud. This secretory layer collapses in the dormant bud. Immature leaves, stipules, and leaf primordia occupy the center of the bud; all lack functional resin glands. In spring, stipules of emerging leaves develop an adaxial palisadelike secretory epidermis that becomes more ridged longitudinally in successive stipules. Marginal teeth of the first leaves to emerge are covered with trichomes and lack a secretory epidermis. In successive leaves the teeth become glandular and secrete resin as the lamina unrolls. Later in the season, marginal leaf glands account for much of the resin. Unspecialized hydathodes or extrafloral nectaries occur proximal to each glandular tip. Guttation of water or nectar occurs here through stomata located above a vein ending. On the basis of field observations and a laboratory feeding experiment, the resin seems to function mainly as an insect repellent. It may also reduce water loss from young leaves.
SYMMETRY AND DEVELOPMENT OF PISTILLATE VALLISNERIA AMERICANA (HYDROCHARITACEAE)
Authors: Wilder George J.
Published: January 2018

Pistillate Vallisneria americana produces upright vegetative axes and prostrate stolons and develops in a manner fundamentally similar to that of Limnobium spongia (Hydrocharitaceae) and certain other taxa of Alismatidae. The cauline portions of pistillate V. americana branch solely by the bifurcation of apical meristems, and their mode of branching offers clues concerning the nature of the plant body. The upright axes are interpreted to have sympodial growth, whereas at least certain stolons appear to be entirely monopodial. The upright axes are either typical vegetative axes or turions; and of these, only turions appear to survive the winter in at least one locality. Pistillate V. americana produces intravaginal squamules (multi‐seriate trichomes) although they appear reduced in number relative to those in certain other hydrocharitaceous and alismatid taxa. Vallisneria americana exhibits a notable degree of mirror image symmetry which differs somewhat from that of Limnobium spongia.
THE ULTRASTRUCTURE OF THE QUIESCENT CENTER IN THE APEX OF CULTURED ROOTS OF CONVOLVULUS ARVENSIS L.
Authors: Phillips Harry L. , Torrey John G.
Published: January 2018

Cultured roots of the common bindweed, Convolvulus arvensis L. growing at the rate of 15–30 mm/day in sterile nutrient medium were fixed for electron microscopic analysis. The ultrastructure of the quiescent center, the initials of the ground meristem, and the initials of the procambium were studied in order to determine whether sequential structural changes could be correlated with models for specifying the mechanisms by which cell differentiation and cell division might be controlled. The differentiation of cells in the root proper occurs very gradually in linear files from the site of the quiescent center proximally into the different tissue regions. Major structural changes, such as the orientation and subsequent elongation of cells along the longitudinal axis of the root and cell wall changes, indicate that the control of differentiation and perhaps cell division occurs in radial gradients outwardly from the quiescent center.
GERMINATION OF HELEOCHLOA ALOPECUROIDES (POACEAE) IN VARIOUS CONCENTRATIONS OF HELIUM, NITROGEN, AND CARBON DIOXIDE
Authors: Holte Karl E. , Mourtsen Peter
Published: January 2018

The percentages of germination of Heleochloa alopecuroides (Pill and Mitterp) Host seeds were tested in various controlled atmospheres of He, N2, and CO2. Atmospheres of 16.7%, 33.3 %, and 88.9 % of each of these gases (thus reducing O2 concentrations to 17.5 %, 14.0 %, and 2.3% respectively) were introduced into 1000‐ml stoppered vacuum flasks, each containing 100 seeds placed on substrates of either sterilized soil or filter paper. The flasks were placed in growth chambers with an 8‐hr light period at 20 C and a 16‐hr dark period at 5 C. The germination rate was accelerated directly with increased concentrations of He and N2 but was retarded by increased percentages of CO2. Control flasks eventually reached nearly the same percentages of germination as those of He and N2 but at a later point in time.
IS THE NUCLEAR DNA CONTENT OF MATURE ROOT CELLS PRESCRIBED IN THE ROOT MERISTEM?
Authors: Evans Lance S. , Hof Jack Van't
Published: January 2018

Cells of the mature root exhibit arrest within the G1 and G2 periods of the mitotic cycle. The number of cells arrested with a 2C or 4C DNA amount in mature tissue was compared with that in meristems of excised primary root tips deprived of carbohydrate. Results from four plant species are described. Cells in mature tissue of seedling roots of Vicia and Pisum exhibited arrest predominately at the 4C while those of Triticum and Helianthus arrested preponderantly at the 2C DNA level. The proportion of cells arrested at the 2C and 4C levels in mature root tissue was specific for each species tested. In each species the cycle stage where most cells arrested was the same in carbohydrate‐deficient root meristems as in mature root tissue; consequently, most meristematic cells are preconditioned or predetermined to arrest in a specific mitotic period. A test system was developed in Pisum in which the predominant period of arrest was altered by the removal of the cotyledons. The predominant arrest period changed from 4C to 2C in both mature root tissue and carbohydrate‐deficient root meristems with cotyledon removal and indicated that mature root cells are preconditioned while meristematic as to where they will eventually arrest in the mitotic cycle.
DIFFERENTIAL RESPONSES TO MAGNESIUM AND CALCIUM BY NATIVE POPULATIONS OF AGROPYRON SPICATUM
Authors: Main John L.
Published: January 2018

Plants of Agropyron spicatum (Pursh) Scribn. and Smith. from populations native to serpentine and nonserpentine soils were grown at varying levels of magnesium and calcium in culture solutions. The yields of plants from the two populations were different. At high Mg levels (low Ca) the yield of the serpentine population was significantly higher than that of the nonserpentine population. At low Mg the yield of the serpentine population leveled off at a Mg: Ca ratio of 1:2, while the yield of the nonserpentine population increased up to a Mg:Ca ratio of 1:8 and showed no leveling off. Chemical analyses of tissue showed that the Ca uptake of plants from the serpentine population was significantly higher than that of the nonserpentine population. In addition, the serpentine population maintained a lower Mg concentration in the shoots than the nonserpentine population at comparable Mg substrate levels. The two populations showed differences in Ca and Mg uptake efficiency and Mg/Ca, Ca + Mg/K + Na, and Ca + Mg + K + Na in the shoots. The ecotypic differentiation with respect to Mg and Ca between native populations of serpentine and nonserpentine A. spicatum does not appear to be due to any single mechanism but, rather, a combination of several possible mechanisms, i.e., differences in root morphology, uptake mechanisms, translocation of nutrients, and interactions between cations.
MORPHOLOGY AND DISTRIBUTION OF COLLETERS AND CRYSTALS IN RELATION TO THE TAXONOMY AND BACTERIAL LEAF NODULE SYMBIOSIS OF PSYCHOTRIA (RUBIACEAE)
Authors: Lersten Nels R.
Published: January 2018

Earlier investigators established that a finger‐like colleter with elongate axial cells and a palisade epidermis is the standard type in the Rubiaceae. This type, with some variation, also prevails in Psychotria, based on a worldwide anatomical survey of vegetative buds from herbarium specimens of 296 species (about 50 % of total). It is virtually the only type found outside of continental Africa. Among African species, it is most common in subgenus Psychotria, with mostly nodule‐free species. In subgenus Tetramerae, with only leaf‐nodulated species, there is a strong tendency toward brushlike and dendroid colleters in which epidermal cells are extremely elongate and separated from each other. It is speculated that this change in colleter morphology associated with presence of nodule bacteria may be correlated with a change in secretion product more suitable for support of bacteria. Three morphological forms of crystal occur: raphides, styloids, clustered crystals. They may occur singly or in combination. Several patterns and trends were noted in crystal distribution that could be of taxonomic significance.
THE DISTRIBUTION OF HETEROCHROMATIN IN THE GENUS NICOTIANA (SOLANACEAE)
Authors: Merritt James F.
Published: January 2018

A survey of the species of the genus Nicotiana was carried out to determine the distribution and the cytological characteristics of heterochromatin in this genus. All examined species of the genus possess knob‐type heterochromatin, which is defined as spherical, densely staining regions of the pachytene chromosomes. These knobs are most frequently located near the centromere, the nucleolar organizer, and the ends of the chromosomes. Block‐type heterochromatin, defined as any longer‐than‐broad heterochromatic segment seen at pachytene, was found in three species of the section Paniculatae, three species of the section Tomentosae, and two species of the section Noctiflorae. Three categories of the block‐type heterochromatin, corresponding to the three subgenera, were found to differ with respect to overall size, staining properties, and location of the blocks. The distribution of these three types of block heterochromatin is discussed in the light of the latest taxonomic treatments of the genus.
A PALYNOLOGICAL INVESTIGATION OF THE GENUS TOURNEFORTIA (BORAGINACEAE)
Authors: Nowicke Joan W. , Skvarla John J.
Published: January 2018

The pollen morphology of 65 species of Tournefortia L. was examined by light, scanning, and transmission electron microscopy. Four distinct morphological types were found: Type I, grains subprolate with 3‐colporate apertures alternating with three pseudocolpi and the ektexine psilate; Type II, grains subprolate, the poles expanded, 3‐colporate with the ektexine psilate polarly and verrucate equatorially; Type III, grains spheroidal with three porate apertures and the ektexine clavate; Type IV, grains suboblate with 3–4 colporate apertures and the ektexine psilate to finely rugose. Type I was found in 46 species representing the most diverse group of tournefortias. Type II was found in 12 species from the Old and New Worlds representing two related groups. Type III was found in five closely related species from the American tropics. Type IV was found in two species from South America, but differences in both the pollen and sporophyte indicate that this grouping may be artificial. Pollen morphology does not support the separation of those species treated as Messerschmidia and confirms the close relationship of Tournefortia and Heliotropium. The striking morphological divergence of Tournefortia pollen raises the question of its adaptive significance.
ANATOMY OF THE GYNOECIUM IN TWO SPECIES OF BAKERIDESIA (MALVACEAE)
Authors: Klotz Larry H.
Published: January 2018

Structure of the gynoecium is described in two species of Bakeridesia, subgenus Bakeridesia (Malvaceae, tribe Malveae). The dorsal wall of each carpel bears a winglike projection with a marginal pair of pubescent, bluntly dentate wings. The projection arises as a single, solid ridge of tissue after the ovules are initiated and after the ventral carpellary margins are fused with the receptacle. Two multiseriate layers of fiber‐sclereids line each locule and continue into the winglike projection where they are separated by parenchyma. Gynoecial vascularization is described in detail. The richly vascularized carpels are supplied by five traces: a median dorsal trace, which bifurcates into two dorsal bundles; two lateral traces; and two ventral traces. Adjacent ventral traces, lateral traces, and septal bundles are fused—i.e., they are held in common by neighboring carpels. The presence of lateral carpellary traces may be a primitive character in the tribe Malveae.
PLASTID INCLUSIONS IN EPIDERMAL CELLS OF BETA
Authors: Hoefert Lynn L. , Esau Katherine
Published: January 2018

Inclusions were found in epidermal plastids of Beta vulgaris L., by the use of the electron microscope. One type of inclusion resembles the membrane‐bound plastid inclusions found by others in various meristematic plant cells; the other does not appear to have been described before. The second type of inclusion is not membrane‐bound and appears elongated and fibrillar in longisection. The elongated plastid inclusion sometimes becomes quite large. It is postulated that Beta epidermal cells may store two different proteins under some conditions.
SURFACE CONFIGURATION OF THE LORICA OF THE EUGLENOID TRACHELOMONAS AS REVEALED WITH SCANNING ELECTRON MICROSCOPY
Authors: Rosowski James R. , Vadas Robert L. , Kugrens Paul
Published: January 2018

The surface of Trachelomonas was examined readily with SEM at magnifications up to X 20,000 in unfixed or fixed material. Cells were placed directly on specimen holders without washing, air dried, and coated with aluminum or gold. Clones of T. grandis, T. hispida var. coronata, and T. oblonga var. punctata and three species from a natural collection showed the following features: the lorica was punctate or solid, and the surface projections, when present, consisted of minute papillae (0.1 μm), larger, often globose papillae (up to 0.8 μm), and spines which tapered to a point or which had parallel sides and ended bluntly; spines appeared hollow or solid. Pringsheim's clone of T. oblonga var. punctata, which he described as a new spineless variety, possessed short tapering spines and globose papillae. Such observations suggest that a major problem in delimiting species may be in discovering the ornamentation potential of a clone. The discovery of new features of the lorica (e.g., minute papillae and hollow projections), the clarification of shapes of surface features, and, in general, the excellent resolution at 10 times the usable magnification of light microscopy dictate a reexamination of known species with SEM. We suggest that a SEM study of the variation in the lorica surface in clonal material will lead to a recognition of polymorphism and eventually to a clearer understanding of taxonomic entities described from natural collections.
THE FROND OF HETERANGIUM
Authors: Shadle Gary L. , Stidd Benton M.
Published: January 2018

Frond members belonging to the monostelic seed fern genus Heterangium have been found in Pennsylvanian age coal balls collected in the Illinois Basin. Petioles bear small pinnae below a dichotomy which produced a bipartite frond. Pinnules of the Sphenopteris obtusiloba type are borne on secondary pinnae. The anatomy of each pinna order and the pinnules is described.
STUDIES ON NITROGEN FIXATION BY ALNUS CRISPA
Authors: Dalton David A. , Naylor Aubrey W.
Published: January 2018

Root nodules of Alnus crispa (Ait.) Pursh were shown to possess a symbiotic nitrogen‐fixing organism. The reduction of acetylene to ethylene, as measured by gas chromatography, was used to determine the presence of the nitrogen‐fixing system. Ethylene production was measured at 5.1 μmoles/g excised nodule · hr for both field and greenhouse plants. The nodules were found to consist of short nubs usually clustered in masses up to 4 cm in diam. Microscopic examination of nodules revealed some cortical cells fully packed with spherical endophyte cells. The outer cortex and radiating arms of cells in the inner cortex remained uninfected. Nodules examined during the winter were found to be shrunken, with a random distribution of endophyte cells. Soil nitrogen measurements indicated that nitrogen fixation activity by A. crispa does not lead to an increase in soil nitrogen above levels in adjacent areas.
THE EFFECTS OF TEN PHENOLIC COMPOUNDS ON HYPOCOTYL GROWTH AND MITOCHONDRIAL METABOLISM OF MUNG BEAN
Authors: Demos E. K. , Woolwine M. , Wilson R. H. , McMillan C.
Published: January 2018

Ten phenolic compounds were examined for their effect on mung bean (Phaseolus aureus L.) hypocotyl growth and on respiration and coupling parameters of isolated mung bean hypocotyl mitochondria. Three compounds—tannic, gentisic, and p‐coumaric acids—inhibited hypocotyl growth and when incubated with isolated hypocotyl mitochondria released respiratory control, inhibited respiration, and prevented substrate‐supported Ca2+ and PO4 transport. Vanillic acid also inhibited hypocotyl growth and reduced mitochondrial Ca2+ uptake but did not affect respiration or respiratory control of isolated mitochondria. This is the first compound reported to selectively inhibit Ca2+ uptake in plant mitochondria. Two other phenolic compounds—α, 3,5‐resorcylic and protocatechuic acids—showed no significant effect on hypocotyl growth and did not affect mitochondrial oxidative phosphorylation either separately or in various combinations. Four phenolic compounds—ferulic, caffeic, p‐hydroxybenzoic, and syringic acids—showed a significant reduction in mung bean hypocotyl growth but did not inhibit any of the mitochondrial processes examined. The results show that phenolic compounds which alter respiration or coupling responses in isolated mitochondria also inhibit hypocotyl growth and may reflect a mechanism of action for these natural growth inhibitors.
EVOLUTIONARY STUDIES OF ATRIPLEX: A RELIC GIGAS DIPLOID POPULATION OF ATRIPLEX CANESCENS
Authors: Stutz Howard C. , Melby James M. , Livingston Gordon K.
Published: January 2018

Growing on shifting sand dunes in central Utah is a small endemic population of a gigas form of A triplex canescens. Whereas normal A. canescens usually grows to a height of three to four feet and occasionally to five or six feet, the gigas form often reaches ten and sometimes twelve feet. All normal A. canescens so far examined (67 populations) have 2n = 36 chromosomes; the gigas form has 2n = 18 chromosomes. Several lines of evidence suggest that the gigas form is a relic diploid and the normal form is an autotetraploid derived from it. The growth rate of seedlings and new twigs is nearly twice as great in the diploid as in the tetraploid. Seed germination is faster and much better in the diploid. The tetraploid is reproductively isolated from the diploid because of a much earlier flowering period. The diploid plants possess many attributes which make them uniquely adapted to the drifting sand dune habitat.
THE FEMALE GAMETOPHYTE OF THREE SPECIES OF GRINDELIA AND OF PRIONOPSIS CILIATA (COMPOSITAE)
Authors: Howe Thomas D.
Published: January 2018

In the four species studied, Grindelia stricta ssp. blakei, G. arizonica, G. lanceolata, and Prionopsis ciliata (Haplopappus ciliatus), the female gametophyte develops according to the Polygonum (normal) type from the chalazal megaspore of a row of four. In most cases only two antipodal cells are formed, the micropylar one originally containing two nuclei. The number of nuclei increases in both cells; one or both antipodal cells typically grow laterally into the integument, often extending to near the surface of the ovule. This resembles the condition previously reported in Grindelia squarrosa. Since the four species of Grindelia have similar antipodal outgrowths, such outgrowths may be considered typical for this genus. The fact that Prionopsis resembles Grindelia in regard to outgrowths from the antipodal cells and differs in this respect from typical Haplopappus helps to justify its separation from Haplopappus, and perhaps its suggested merger with Grindelia.
A LIGHT AND ELECTRON MICROSCOPIC STUDY OF PEROXIDASE LOCALIZATION IN THE ONION ROOT TIP
Authors: Goff Charles W.
Published: January 2018

Peroxidase activity in the onion root tip was localized by the diaminobenzidine procedure and studied at the light and electron microscope levels. Reaction product was observed in the cell wall, on the plasmalemma, in the Golgi apparatus cisternae and vesicles, in young and developing vacuoles, in the endoplasmic reticulum, and on both soluble and membrane‐bound ribosomes. The reaction product at the various cellular and subcellular sites occurs in distinct tissue and developmental patterns.
ECCENTRIC SECONDARY GROWTH IN CORDYLINE AND OTHER AGAVACEAE (MONOCOTYLEDONAE) AND ITS CORRELATION WITH AUXIN DISTRIBUTION
Authors: Fisher Jack B.
Published: January 2018

Eccentric secondary growth is described and illustrated in detail for the first time in horizontal stems of Cordyline, Dracaena, Yucca and Beaucarnea (= Nolina) with up to 13 times more secondary tissues on the lower side than on the upper side. In Cordyline the secondary tissues on the lower side are rhizome‐like in having less lignification of ground parenchyma and more diffuse and smaller secondary bundles than in the vertical stem. In Cordyline, Yucca, Beaucarnea, and D. reflexa the ground parenchyma cells are larger on the lower side. The vascular bundles are significantly larger on the lower sides of Beaucarnea and D. reflexa and are smaller on the lower side of D. fragrans. The occurrence of growth rings and eccentric growth is related to changes in cambial activity. There is close correspondence between enhanced cambial activity and high auxin levels on the lower side which have been reported elsewhere. However, there is no evidence of reaction wood tracheids on either the upper or lower sides.
THE SHOOT APEX OF HYMENAEA COURBARIL (LEGUMINOSAE)
Authors: Stein Otto L.
Published: January 2018

Shoot apices of Hymenaea courbaril are representative of those of many distichous plants, showing sharp intraplastochronic changes as a result of differential growth of the most recently formed primordium and the apical meristem proper. However, an unusual feature of this species is the complex arrangement of stipules. These enclose their own leaves as well as younger structures. Furthermore, the midregions of the stipules fuse ontogenetically at their bases, separating the newly formed leaf from the young shoot. Examination of apices of H. courbaril and H. stilbocarpa with the SEM shows similar morphological features in these two species.
EFFECTS OF PHENOLIC INHIBITORS ON GROWTH AND METABOLISM OF GLUCOSE‐UL‐14C IN PAUL'S SCARLET ROSE CELL‐SUSPENSION CULTURES
Authors: Danks Maureen L. , Fletcher John S. , Rice Elroy L.
Published: January 2018

ABSTRACT

Paul's Scarlet rose cell‐suspension cultures were incubated in varying concentrations of the following phenolic inhibitors; chlorogenic acid, cinnamic acid, p‐coumaric acid, ferulic acid, and scopoletin. All test compounds except chlorogenic acid were completely inhibitory at a 10−3m concentration, resulting in death of the cells prior to completion of the growth cycle. To assess the cellular effects of two commonly named plant inhibitors, ferulic and cinnamic acids, these compounds were provided to cultures during incubation of cells with glucose‐UL‐14C. Incubation of cells with glucose‐UL‐14C in the presence of 10−4m ferulic acid resulted in increased incorporation of 14C into the soluble lipid fraction along with decreased incorporation of 14C into protein, organic acids, and soluble amino acids. Treatment of the cells with 10−5m cinnamic acid during the incubation period resulted in a significant decrease in incorporation of 14C into protein. These alterations in the flow of carbon into cellular constituents when cells are treated with cinnamic and ferulic acids explain, at least in part, why these compounds inhibit growth, seed germination, and seedling development.
FINE STRUCTURE OF THE ZYGOTE AND EARLY EMBRYO IN QUERCUS GAMBELII
Authors: Singh A. P. , Mogensen H. Lloyd
Published: January 2018

This investigation begins with the late zygote and traces ultrastructural development to the late globular stage of the embryo. Two nucleoli and satellite nucleoli sometimes occur in the zygote nucleus. Mitochondria, dictyosomes, cytoplasmic ribosomes, rough ER, and lipid bodies are numerous in the zygote. Microbodies are occasionally seen. The cell wall becomes well developed before the first division. No plasmodesmata occur in the zygote wall. The basal cell of the proembryo and the suspensor cells of the later embryo have very dense cytoplasm with a high concentration of cytoplasmic ribosomes. The nuclei are very electron opaque. The terminal cell and the cells of the embryo proper have a fine structure similar to that of the zygote. Plastids increase in number, size, starch content, and amount of thylakoid lamellae as the embryo develops. Mitochondria are numerous and appear active at all stages. Dictyosome activity, ribosomal aggregation, and the amount of ER are highest during the late globular stage. Lipid bodies are present up to the early globular stage, then disappear. The inner cell walls of the embryo are thin and have many plasmodesmata. These walls begin to thicken at the late globular stage, and at this time the size of the embryo begins to show an increase over that of the zygote. The results show a corresponding increase in the amount and activity of the metabolic machinery as the development of the embryo progresses. Lipids are probably more important as a nutrient source in the zygote and early embryo; starch becomes more important in the late stages. Absorption of nutrient material into the embryo sac and developing embryo appears to be from the chalazal end.
POLLINATION ECOLOGY OF PYRRHOPAPPUS CAROLINIANUS (COMPOSITAE)
Authors: Estes James R. , Thorp Robbin W.
Published: January 2018

Pyrrhopappus carolinianus and Hemihalictus lustrans constitute a mutualistic association: the early morning flowering of Pyrrhopappus provides the matinal bee with a nearly exclusive pollen source, although other plants must be visited for nectar. Female Hemihalictus, the primary pollen vector, tear open the anthers and remove the pollen before it is available to other bees. The foraging behavior of the bee insures cross‐pollination. The flight pattern of the bees generally restricts the pollen dispersal range. If cross‐pollination fails, then autogamy results from twisting of the styles that brings the stigmas in contact with the pollen presented on the styles of other florets. Schinia mitis is an important predator of the capitulae of P. carolinianus.
GENERIC RELATIONSHIPS OF DECASCHISTIA (MALVACEAE) AND THE DESCRIPTION OF A NEW TRIBE, DECASCHISTIEAE
Authors: Fryxell Paul A.
Published: January 2018

The Asiatic genus Decaschistia has traditionally been placed in the tribe Hibisceae, but it is shown that this genus has a combination of characters that does not permit it to be accommodated either in the Hibisceae or in any other tribe of the Malvaceae. A new tribe, the Decaschistieae Fryx., is therefore described and distinguished from the other four tribes currently accepted in the Malvaceae.
CONIFER WOOD FROM THE UPPER JURASSIC OF UTAH PART I: XENOXYLON MORRISONENSE SP. NOV.
Authors: Medlyn David A. , Tidwell William D.
Published: January 2018

A new species of conifer wood,Xenoxylon morrisonense, is described from the Morrison Formation on the Colorado Plateau. It is compared with other species ofXenoxylon, withX. latiporosumbeing the closest.Xenoxylon morrisonensediffers fromX. latiporosumin its marked indentations, simple pits on the horizontal and tangential walls of ray cells, absence of crassulae, presence of wood parenchyma, and thin borders on podocarpoid type crossfield pits. The origin of the septa in the tracheids is summarized, and the possible affinity ofXenoxylonwith the Podocarpaceae is considered.
GAMETOPHYTES AND EMBRYOS OF ACTINOSTACHYS PENNULA, A. WAGNERI, AND SCHIZAEA ELEGANS, WITH NOTES ON OTHER SPECIES
Authors: Bierhorst David W.
Published: January 2018

Gametophytes and embryos of Actinostachys wagneri, A. pennula, and Schizaea elegans are described along with a few observations on those of 5. dichotoma, A. digitata, A. spirophylla, Ophioglossum pendulum, Danaea simplicifolia, Botrychium virginianum, B. dissectum, and Psilotum nudum. Variation in the gametophyte and embryo at the interspecific level within the Schizaeaceae is discussed.
SOME ULTRASTRUCTURAL OBSERVATIONS ON ENDODERMAL CELL DEVELOPMENT IN ZEA MAYS ROOTS
Authors: Haas David L. , Carothers Zane B.
Published: January 2018

The fine structure of primary, secondary, and tertiary stages of Zea endodermal cell development was investigated. The casparian strip formed in situ in the anticlinal walls and remained at a fixed point relative to the endodermis‐pericycle boundary. The only protoplasmic structure that had a constant spatial association with the developing strip was the plasmalemma. Plasmodesmata appeared to be more numerous on the tangential walls than on radial walls; only rarely were they located in the casparian strip. The suberized lamella developed on inner and outer tangential walls before it appeared on the radial walls. No cytoplasmic organelles were found to have any particular spatial association with this layer. The suberized lamella was about 0.04 μm thick except near plasmodesmata and along the adaxial margin of the casparian strip, where it was thicker. Occasionally it failed to form along the abaxial margin of the strip. The adherent affinity between plasmalemma and casparian strip was lost after the strip was covered by suberized lamella. The secondary wall became asymmetrically thickened by differential deposition of successive lamellae. A thin layer of secondary wall material extended across the floor of each pit. Pit cavities often contained mitochondria, and plasmodesmata were restricted to the pits. The plasmodesmata were constricted where they entered the thin layer of secondary wall material and where they penetrated the suberized lamella. The various stages of cell development tended to be asynchronous. No passage cells were observed. Endodermal cell development in Zea closely resembles that described for barley.
THE ULTRASTRUCTURE OF CRUCIFORM NUCLEAR DIVISION IN SOROSPHAERA VERONICAE (PLASMODIOPHOROMYCETE)
Authors: Braselton James P. , Miller Charles E. , Pechak David G.
Published: January 2018

Vegetative nuclear divisions in cystosoral Plasmodia from the shoot system ofSorosphaera veronicaeSchroeter were studied with standard transmission electron microscopy. Each metaphase nucleus forms a cruciform configuration as the persistent nucleolus elongates perpendicularly to chromatin aligned on the equatorial plate. The nuclear envelope remains intact during metaphase and anaphase. Each spindle pole consists of a fenestrated nuclear envelope with an exteriorly situated centriole and closely associated endoplasmic reticulum. Intranuclear membranous vesicles occur within metaphase and anaphase nuclei and are closely associated with chromatin and nuclear envelope. Microtubules pass from centrioles into the nucleus and are also attached to chromatin at kinetochores.
A QUANTITATIVE ANALYSIS OF THE MEGAGAMETOPHYTE OF FIVE SPECIES OF CORNUS L.
Authors: Smith Bruce B.
Published: January 2018

Comparisons of variations of morphological features, treated quantitatively, of the megagametophytic stages in Cornus asperifolia Michaux., C. stricta Lam., C. amomum Miller, C. florida L., and C. alternifolia L. suggest differences in growth patterns of their megagametophytes. The successful application of the clearing fluid 41/2 (Herr Fluid) affords adequate data for assessment of quantitative features of such minute plants. This method, less time consuming than traditional paraffin sectioning techniques, allows for statistical treatment of a sufficient number of species for valid inferences of angiospermous embryological features. An investigation of megagametophytic size was directed both to successive stages within each species and to each stage among all five species. In both instances, means, confidence intervals (CI), and growth increments (GI) were compared. Without exception, the largest means for length and width occurred in the 8‐nucleate stage for all species. The greatest GI for length occurred in the 8‐nucleate stage for C. stricta, C. alternifolia, and C. asperifolia and in the 4‐nucleate stage for C. florida. The 4‐ and 8‐nucleate GI were nearly equal for C. amomum. Overlapping of 95 % CI between successive stages indicated uniform growth between stages for the megagametophyte. Only C. asperifolia had CI overlapping between all successive stages for length and width. These five species are clearly separated on the basis not only of variations in qualitative features but also on megagametophytic growth patterns among species.
VARIATIONS IN ANATOMY, ASSOCIATIONS, AND ORIGINS OF KRANZ TISSUE
Authors: Brown Walter V.
Published: January 2018

Although the unique tissue required for C4 photosynthesis in nonsucculent plants is often described as being modified leaf parenchyma sheath, which is positioned meaningfully between the mesophyll externally and the vascular tissues internally, the actual range of locations and known associations make that concept untenable. In origin the Kranz tissue develops from procambium as well as ground parenchyma. It is found in stems as well as leaves. In position Kranz tissue can lie in the parenchyma sheath, in the mestome sheath, isolated in the mesophyll, peripherally in some thick leaves, or within the veins. It can be associated with mesophyll only, mesophyll and colorless parenchyma, mesophyll and sclerenchyma, other Kranz tissue and vascular tissues, mesophyll and mestome sheath, mesophyll and phloem, mesophyll and xylem, epidermis, and, finally, mestome sheath and xylem and phloem. The use of the term Kranz is expounded.
STUDIES ON THE FLORAL ANATOMY OF THE CUNONIACEAE
Authors: Dickison William C.
Published: January 2018

Twenty‐two genera representing sixty‐two species of Cunoniaceae and Davidsonia were examined with respect to floral anatomy. Sepals are vascularized by three traces with the lateral traces of adjacent sepals united. Pancheria is unique for the family with species in which the sepals are vascularized by a single, undivided bundle. Petals, when present, and stamens, are uniformly one‐trace structures. A general tendency exists within the family for the principal floral bundles to unite in various ways, with fusions evident between calyx, corolla, and androecial vascular supplies. Carpel number ranges from two to five and the gynoecium is generally surrounded by a prominent disc. Gynoecia of Ceratopetalum and Pullea are “half‐inferior.” The number of ovules per carpel locule ranges from one to numerous. Ventral carpel sutures range from open to completely sealed at the level of placentation. Carpels of the apocarpous genus Spiraeanthemum (incl. Acsmithia) are vascularized by a dorsal bundle and either three or four bundles constituting the ovular and wing vasculation in the ventral position, a condition unlike other members of the family. Ovules are supplied by the median ventral bundle. More advanced bicarpellate gynoecia within the family are predominately vascularized by a dorsal and two ventral bundles although a variable number of additional lateral wall traces may be present. A major trend exists toward fusion of the ventral bundles of adjacent carpels in the ovary of both bicarpellate and multicarpellate plants. At the base of the styles the fused ventral strands separate and extend along with the dorsal carpellary bundles into styles of adjacent carpels. In Pullea the ventral bundles terminate within the ovules. The united ventral carpellary bundles in Aphanopetalum, Gillbeea, and Aistopetalum lie in the plane of the septa separating adjacent carpels. Ovules are vascularized by traces originating from the vascular cylinder at the base of the gynoecium or by traces branching from the ventral bundles. Ovular traces in each carpel are united, or remain as discrete bundles, prior to entering the placenta. Tannin and druses are common throughout all floral parts. Although floral anatomy generally supports the position of Cunoniaceae near Saxifragaceae and Davidsoniaceae, the evolutionary relationship of the Cunoniaceae to the Dilleniaceae is uncertain.
CHROMOSOME BEHAVIOR IN HYBRID FERNS: A REINTERPRETATION OF APPALACHIAN DRYOPTERIS
Authors: Hickok Leslie G. , Klekowski Edward J.
Published: January 2018

Analyses of chromosome pairing behavior in fern hybrids, as evidenced by the degree of bivalent and/or univalent formation at meiotic prophase, have frequently been employed in studies of evolutionary relationships within polyploid fern complexes. Pairing is often seen to involve genomic numbers of chromosomes. Many examples exist, however, that indicate pairing on subgenomic levels. If this type of behavior is not recognized in analyses of F1 hybrids and their polyploid derivatives, interpretations of evolutionary relationships based upon pairing behavior may be misleading. Contrary to some views, sterile triploid hybrids possessing less than three distinct genomes may play a significant role in the formation of reticulate polyploid complexes. This possibility must be considered in interpretations of these complexes. With these factors in mind, the Appalachian Dryopteris complex has been reinterpreted. The reinterpretation provides explanations for several unexplained inconsistencies in previous interpretations.
PHYSIOLOGICAL RESPONSES TO RAINFALL IN OPUNTIA BASILARIS (CACTACEAE)
Authors: Szarek Stan R. , Ting Irwin P.
Published: January 2018

An immediate, marked response to small amounts of rainfall occurs in Opuntia basilaris, despite previous drought conditions. The effect of rainfall is upon plant water potential, which is the single most important parameter influencing stomatal opening, CO2 assimilation, and organic acid synthesis. Nocturnal stomatal opening is initiated following rainfall, and stomata remain open during the daytime. Decreasing stomatal and mesophyll resistances correlate with increasing rates of nocturnal assimilation of 14CO2. Photosynthetic rates of 14CO2 assimilation are low, despite high plant water potentials and low stomatal diffusion resistances. The decreased mesophyll resistances and increased rates of nocturnal 14CO2 assimilation correlate with the increases of nocturnal efficiency of water use and CO2 assimilation. The diurnal efficiency of water use and CO2 assimilation is lower than the nocturnal gas exchange efficiency values.
SEED DORMANCY IN ISANTHUS BRACHIATUS (LABIATAE)
Authors: Baskin Jerry M. , Baskin Carol C.
Published: January 2018

Seed dormancy and its ecological aspects were investigated in Isanthus brachiatus, a summer annual plant of limestone outcrops in southeastern United States. Freshly matured seeds are dormant and exhibit physiological polymorphism with respect to the conditions necessary to overcome dormancy. Fifteen to thirty‐five percent of the seeds in a seed crop require only one stratification treatment and germinate the first spring following their dispersal in autumn. The remainder of the seeds require two, three, or more stratification treatments and thus do not germinate until after two, three, or more overwintering periods in the field. In those seeds that require more than one stratification treatment to overcome dormancy, the stratification periods must be separated by a “rest” period, which in nature corresponds to summer. The ecological significance of this type of seed dormancy mechanism in I. brachiatus is discussed in relation to adaptation to its habitat.
HAPLOIDY IN HAPLOPAPPUS GRACILIS (N = 2)
Authors: Jackson R. C. , Jordan R. G.
Published: January 2018

Analysis of meiosis in a haploid (monoploid) sporophyte of Haplopappus gracilis (n = 2) showed a nonrandom distribution of chromosomes at anaphase I. Chromosomes A and B were associated at various prophase I stages in 34 % of the microsporocytes. Presumably, this association persisted long enough to disrupt random distribution in a portion of those meiocytes showing such an association. Pollen stainability of 26.5 % in the haploid was in agreement with the normal expectation. However, this number resulted from a nonrandom chromosome distribution. The usual method of predicting fertility of haploids, 1/2n, is not accurate for monoploids with low chromosome numbers, and more functional methods are proposed.
DORMANCY AND GERMINATION OF COMMON RAGWEED SEEDS IN THE FIELD
Authors: Willemsen Roger W.
Published: January 2018

Common ragweed (Ambrosia artemisiifolia) seeds were stored under natural environmental conditions by placing them at three soil levels (surface, 5 cm, and 15 cm) in the field on November 1, 1972. Germination tests at 4‐week intervals indicated that dormancy was broken by the end of January. Germination was initially greater at high temperatures, but this difference decreased with increasing time in the field. Secondary dormancy was evident in surface seeds by March 21 but not until April 18 at 5 cm and June 13 at 15 cm. Germination in the field was greatest at the surface but was observed at all soil levels by March 21. Seedling survival was 68% at the surface and 0% at 5 and 15 cm on June 13. Maximum and minimum soil temperatures were recorded at each soil level during the experiment and were correlated with the results. Greater germination and survival at the surface supports the evidence for ragweed's dependence on soil disturbance for germination, and the induction of secondary dormancy explains why ragweed does not constitute a dominant part of the vegetation when disturbance occurs after the soil warms to a critical point in the summer.
CHROMOSOME COUNTS IN CHEILANTHES AND ASPIDOTIS WITH A CONSPECTUS OF THE CYTOLOGY OF THE SINOPTERIDACEAE
Authors: Knobloch Irving W. , Tai William , Adangappuram Thamby Ninan
Published: January 2018

Confirmatory, corrective and new chromosome counts are listed for species in the genus Cheilanthes, and a new chromosome count is given for a member of the genus Aspidotis. An analysis of five collections of C. castanea revealed no significant morphological differences despite the different chromosome numbers. The ploidy level of all known species in genera of the Sinopteridaceae is summarized, revealing directions in which future research might proceed to complete our cytological knowledge of this family.
MORPHOGENETIC STUDIES ON HAWORTHIA: EFFECTS OF INOSITOL ON GROWTH AND DIFFERENTIATION
Authors: Kaul K. , Sabharwal P. S.
Published: January 2018

Effects of inositol on growth and differentiation of Haworthia tissue were studied. Inositol was found to be essential for the survival of the tissue. Growth was increasingly better with the increase in inositol content of the medium. A minimum level of inositol was required for organ differentiation. Organ differentiation was also promoted by the increase in inositol concentration in the medium. The chlorophyll content of the tissue increased with the increasing concentration of inositol. Presence of 2‐deoxyglucose in the inositol‐containing medium led to inositol deficiency symptoms.
FLORAL ANATOMY IN THE SAXIFRAGACEAE SENSU LATO. II. SAXIFRAGOIDEAE AND ITEOIDEAE
Authors: Bensel Carolyn R. , Palser Barbara F.
Published: January 2018

The floral anatomy and morphology of 26 species from the Saxifragoideae and three from the Iteoideae are described and compared. The flowers of the Saxifragoideae are predominantly actinomorphic, partially epigynous and/or perigynous, and pentamerous, with two carpels which bear numerous ovules. There is usually some degree of independence between carpels, and the normally separate styles possess both a canal and transmitting tissue. Generally, staminodia are absent and nectariferous tissue, which is not vascularized, is present. The subfamily is characterized by large multicellular trichomes with globular, often glandular, heads. Placentation may be parietal, axile, or transitional between the two; parietal appears to be a derived condition in the subfamily. The vascular cylinder in the pedicel generally consists of several to many discrete bundles from which diverge ten compound traces at the base of the receptacle, leaving an inner cylinder of vascular strands that coalesce at a higher level into either as many ventral bundles as carpels or twice that number. In the former case, each ventral bundle consists of one‐half of the vascular supply to each adjacent carpel and separates into individual ventral strands in the distal half of the ovary. The ventral bundles provide vascular traces to the ovules and, along with the dorsals, extend up the style to the stigma. Each trace diverging in a sepal plane typically supplies one or more carpel‐wall bundles, a median sepal bundle, and a stamen bundle. Each petal‐plane trace usually provides one or more carpel‐wall bundles, a lateral trace to each adjacent sepal, a petal bundle and, in flowers with ten stamens, a stamen bundle. Dorsal carpel bundles are usually recognizable and may originate from traces in either perianth plane. While the position of Ribes remains problematical, its floral structure does not easily exclude it from the Saxifragoideae. Floral structure in the Iteoideae is remarkably similar to that in the Saxifragoideae, the main differences being a lesser degree of independence between carpels, generally narrower placentae with somewhat fewer ovules, and the presence of only unicellular, acutely pointed epidermal hairs as opposed to the relatively complex, multicellular trichomes prevalent in the Saxifragoideae.
THE ULTRASTRUCTURAL DEVELOPMENT OF THE DIMORPHIC PLASTIDS OF ZEA MAYS L.
Authors: Kirchanski Stefan J.
Published: January 2018

The development of the dimorphic chloroplasts of Zea mays L. in adult foliage leaves is described, and a method of correlating ultrastructural stages by means of leaf chlorophyll is presented. In addition, the developmental changes in chlorophyll a/b ratio are discussed. Both the mesophyll and the bundle sheath plastids contain small grana at the earliest stages of plastid development. As the plastids enlarge, the mesophyll grana stacks increase in both length of the appressed membrane and in the number of thylakoids per granum. Initially, the grana stacks in the bundle sheath plastids also enlarge, but as the plastids approach full size, most of the membrane appression is lost. However, the remaining areas of appression in the bundle sheath plastids show an increase in the number of thylakoids in each small granum.