bluuebunny/crossref_metadata_2025 huggingface dataset:
TAXONOMIC CONSIDERATIONS FOR CARBONIFEROUS COALIFIED COMPRESSION EQUISETALEAN STROBILI
Authors: Gastaldo Robert A.
Published: January 2018

Equisetalean strobili normally are encountered as disarticulated organs. This condition has necessitated the creation of 12 form genera to accommodate the various morphological architectures and anatomical configurations. Taxonomically useful characteristics, which are discernable in permineralized specimens, are rarely distinguishable in coalified compressions due to their destruction during diagenesis and coalification. Therefore, genera established on the position of sporangiophore‐trace origin, such as Schimperia Remy and Remy, are untenable when dealing with coalified compressions. Although the two largest genera of strobili, Calamostachys Schimper and Palaeostachya Weiss, may be synonymous, it is proposed that these form genera be retained when dealing with coalified compression specimens. Each genus provides a particular architectural concept for specimens which may not be assignable to the species level. Calamostachys and Palaeostachya are highly overspeciated genera. It is suggested that characteristics necessary to delimit new species include bract height, degree of bract fusion, disposition of bracts, bract: sporangiophore ratio, number of sporangia per sporangiophore, and sexual status.
POLLEN MORPHOLOGY OF THE CHLORAEINAE (ORCHIDACEAE: DIURIDEAE) AND RELATED SUBTRIBES
Authors: Ackerman James D. , Williams Norris H.
Published: January 2018

Pollen organization and morphology of the South American Chloraeinae (Orchidaceae) was examined by scanning electron microscopy and compared with that of the remainder of the otherwise Australasian Diurideae. All five genera of the Chloraeinae, Bipinnula, Chloraea, Codonorchis, Gavilea, and Geoblasta, and at least one genus from each of the other subtribes were sampled. The Australasian Diurideae are diverse in pollen organization and morphology. The two genera of the Acianthinae, Corybas and Acianthus, have very different pollen and their classification is questioned. Monad pollen organization of Pterostylis (Pterostylidinae) is reinterpreted as primitive and not secondarily derived. Pollen of the Chloraeinae is uniform in exine morphology and organization. Most species sampled have reticulate pollen which tends to be foveolate distally. The basic pollen unit of all Chloraeinae is the tetrad, except Codonorchis which possesses monads. Pollen morphology and organization of the Chloraeinae is most similar to the Caladeniinae, which supports the contention that the Chloraeinae including Codonorchis should be retained in the Diurideae.
CYTOPHOTOMETRIC DETERMINATION OF THE AMOUNT OF DNA IN ARACHIS L. SECT. ARACHIS (LEGUMINOSAE)
Authors: Resslar P. M. , Stucky J. M. , Miksche J. P.
Published: January 2018

The 2C amounts of DNA for 12 taxa of the section Arachis nom. nud. of the genus Arachis L. were determined using cytophotometric techniques. The diploid taxa ranged from 4.92 to 5.98 pg of DNA per cell. The species of the diploid series Annuae Krap. & Greg. nom. nud. averaged ca. 1 pg less DNA per cell than the taxa of the diploid series Perennes Krap. & Greg. nom. nud. No significant differences were found between taxa within these two series. The tetraploid taxa ranged from 10.36 to 11.35 pg of DNA per cell. Within the tetraploid series Amphiploides Krap. & Greg. nom. nud. differences were found between A. monticola Krap. & Rig. and A. hypogaea L. The two subspecies of A. hypogaea, ssp. hypogaea and ssp. fastigiata Waldron, were found to differ significantly in their 2C amounts of DNA. The implications of the cytophotometric data on the chromosomal evolution of this section are discussed.
CELLULAR SLIME MOLDS OF SWITZERLAND. II. DISTRIBUTION IN FOREST SOILS
Authors: Traub Franz , Hohl Hans R. , Cavender James C.
Published: January 2018

A detailed analysis of occurrence and distribution of cellular slime molds in soils of different forest types of Switzerland is given. Specific prevalence patterns representative for each forest type were determined. The degree of complexity of these prevalence patterns parallels tree diversity of the respective forest communities. A comparison of the prevalence patterns shows that by proceeding from species‐rich to species‐poor sites the frequent and common species disappear, whereas the infrequent and rare species are conserved. Thus, these latter species, which probably represent specialists, appear to be of considerable ecological significance.

Dictyostelium mucoroides is the overwhelming dominant in all forest types. Polysphondylium violaceum and D. minutum are abundant in the deciduous forests. These three species account for 87% of the clones isolated. Two species are characteristic of conifer forests, D. aureo‐stipes var. Helvetium and D. polycarpum. Other species encounterd and listed in decreasing order are D. fasciculatum. P. filamentosum, D. sphaerocephalum, D. giganteum, Acytostelium leptosomum, D. aureum var. luteolum and D. polycephalum. Diversity of species is greatest in the mesic beech forests of the Midland, Jura or Forealps regions but reduced populations containing unique cellular slime molds occur in the highest spruce, larch, and pine forests of the Alps.
THE TAXONOMIC IMPLICATIONS OF POLLEN MORPHOLOGY IN SOME SOUTH AMERICAN SPECIES OF MIMULUS (SCROPHULARIACEAE)
Authors: Argue Charles L.
Published: January 2018

The pollen grains of South American hexaploid representatives of the Mimulus glabratus complex, section Simiolus, and M. bridgesii, a South American species sometimes included in this complex and sometimes in section Paradanthus, were examined by light and scanning electron microscopy. Mimulus bridgesii has (6‐) 4–5‐zoniaperturate grains nearly identical to those observed in a complex of species in section Paradanthus. South American members of the M. glabratus complex (M. bridgesii excluded) have the irregularly synaperturate, ± spiraperturate pollen typical of section Simiolus (sensu Grant). Treatment of M. bridgesii as a palynologically aberrant member of section Simiolus is not supported by what is known about the evolution of pollen types in Mimulus and the evolution and dispersal of the M. glabratus complex.
EMBRYOGENY AND REPRODUCTIVE BIOLOGY OF BOTHRODENDROSTROBUS MUNDUS (LYCOPSIDA)
Authors: Stubblefield Sara P. , Rothwell Gar W.
Published: January 2018

Permineralized lycopsid megagametophytes and embryos from Upper Carboniferous strata (Westphalian A) at Burnley, England have been found within isolated megaspores assignable to Setosisporites. The specimens illustrate for the first time the reproductive biology and embryogeny of a free‐sporing, bisporangiate, Paleozoic lycopod, and permit reinterpretation of the megagametophyte of Bothrodendrostrobus. Megagametophyte development is entirely endosporal. Embryogeny is comparable to that of the extant genus Isoetes, and is fundamentally different from that of the fossil lycopsid, Lepidocarpon—Lepidophloios. This further illustrates the diversity among Paleozoic lycopods and helps to clarify relationships among both fossil and extant lycopsid taxa.
NITROGEN FIXATION RATE AND CHLOROPHYLL CONTENT OF THE LICHEN PELTIGERA CANINA EXPOSED TO SULFUR DIOXIDE
Authors: Henriksson Elisabet , Pearson L. C.
Published: January 2018

In general, the rate of nitrogen fixation decreased when the lichen Peltigera canina (L.) Willd. was exposed to sulfur dioxide gas at levels from 0.1 to 500 ppm; at 30 ppm, however, nitrogen fixation was stimulated. Chlorophyll content decreased as level of sulfur dioxide increased.
THE INTERACTION OF AUXIN AND ETHYLENE IN THE MAINTENANCE OF LEAF BLADE FORM IN PHASEOLUS VULGARIS L. VAR. PINTO
Authors: Hayes Alice Bourke
Published: January 2018

Auxin treatment results in hyponastic curvature of the primary leaves of Phaseolus vulgaris L. var pinto. Ethylene production by hyponastic leaves is detected within 1 hr after treatment with IAA in concentrations at or above 1 μm. The amount of ethylene detected is proportional to the concentration of auxin applied. Untreated control leaves and leaves treated with 2,3,5‐tri‐iodobenzoic acid or gibberellic acid did not produce ethylene detectable by our equipment. The hyponastic curvature induced by auxin treatment can be inhibited by exogenous application of ethylene or ethylene‐generating compounds, and these treatments produce epinasty in auxin‐treated leaves. Treatment with inhibitors of ethylene synthesis or action, such as aminoethoxy‐vinylglycine, carbon dioxide, or heat treatment, prolong hyponasty. The planar form, therefore, appears to be affected by both hyponastic auxin effect and an epinastic ethylene effect.
PSEUDOFAGUS IDAHOENSIS, N. GEN. ET SP. (FAGACEAE) FROM THE MIOCENE CLARKIA FLORA OF IDAHO
Authors: Smiley Charles J. , Huggins L. Maurice
Published: January 2018

A new genus and species of Fagaceae are established for compressed leaves and attached fruits which represent one of the dominant taxa in the rich Miocene Clarkia flora of northern Idaho. The leaf and fruit morphology, cuticular and pericarp anatomy, and leaf phytoliths fall within the range of variation of the subfamily Fagoideae. The unique fruit consists of a large, exposed, distinctly keeled, trigonous nut and a diminutive basal cupule. The cupule has an apical frill of free, petiolate, leaflike appendages but lacks other ornamentation, and there is no evidence of a distinct Valvation. As no other genus of the Fagaceae has fruits with this combination of characters, a new genus is established and is referred to the subfamily Fagoideae. The Miocene genus seems most closely related to the extant genus Fagus.
CAVITY FORMATION IN WINTER BUDS OF PINUS BANKSIANA
Authors: Cecich Robert A.
Published: January 2018

The formation of a cavity between the rib meristem and the pith in winter buds of Pinus banksiana is described. Necrosis of cells at the juncture of the rib meristem and pith begins in November, and by mid‐March the necrotic region enlarges, forming a cavity that separates the rib meristem from the pith. The cavity appears to be formed by autolysis, rather than a pulling apart of the cells. The function of the cavity remains speculative.
EFFECT OF TEMPERATURE AND PHOTOPERIOD ON GROWTH AND DORMANCY OF BETULA PAPYRIFERA
Authors: Downs R. J. , Bevington J. M.
Published: January 2018

The effects of day/night temperatures and photoperiod on the growth and dormancy of paper birch (Betula papyrifera) were studied in seedlings from different geographic origins. The response of Alaskan plants to temperature and photoperiod was distinctly different from other seed sources. Alaskan plants required very long days to prevent cessation of growth while plants from southern seed sources grew on photoperiods as short as 14 hr. Low night temperature (14 C) antagonized the promotive action of long photoperiods in Alaskan plants but had little effect in other seed sources. High day temperatures offset the inhibitory effect of the cool night to a lesser degree in Alaskan plants than in plants from other locations. Dormancy induced by short photoperiods was antagonized (relieved ?) to a lesser degree by high night temperatures in Alaskan birch than in other seed sources. Betula papyrifera var. humilis from Alaska may be an incipient species since its morphological traits are accompanied by adaptive physiological responses to its environment. These responses are as distinct as its morphological characteristics.
DIFFERENCES IN BIOMASS ALLOCATION TO REPRODUCTIVE AND VEGETATIVE STRUCTURES OF MALE AND FEMALE PLANTS OF A DIOECIOUS, PERENNIAL HERB, SILENE ALBA (MILLER) KRAUSE
Authors: Gross Katherine L. , Soule Judith D.
Published: January 2018

The pattern of biomass allocation of males and females and the sex ratio and growth characteristics of plants from three seed‐size classes in Silene alba were investigated in a greenhouse study. Seed size significantly affected adult plant size and flower production of both male and female plants, but there was no significant difference in the proportion of males and females emerging in three seed‐size categories. Male and female plants differed in the proportion of total biomass allocated to vegetative and reproductive structures and these differences were consistent across all seed‐size categories. Males allocated a greater proportion of their biomass to flowers than did females. Female reproductive effort was dependent upon the percentage of flowers producing mature capsules. Only females with greater than 20% fruit set have a higher reproductive expenditure than males. Consequently, female expenditure is potentially greater than males, but is spread out over a longer portion of the growing season. This difference in the timing of reproductive expenditures by males and females allows females to allocate more biomass to growth during the early flowering period and may therefore account for the common pattern in herbaceous perennial dioecious species in which adult females are larger than adult males.
SOMATIC EMBRYOGENESIS AND PLANT REGENERATION FROM TISSUE CULTURES OF PENNISETUM AMERICANUM, AND P. AMERICANUM x P. PURPUREUM HYBRID
Authors: Vasil Vimla , Vasil Indra K.
Published: January 2018

Immature embryos as well as explants obtained from young inflorescences of Pennisetum americanum (pearl millet) give rise to callus tissues on nutrient media containing 2,4‐dichlorophenoxyacetic acid (2,4‐D). A compact and pale‐yellow callus that arises from the peripheral cells of the scutellum, and from the young inflorescences, undergoes further organized growth. When transferred to a 2,4‐D‐free medium, supplemented with indole‐acetic acid or kinetin, or both, embryoids are formed in the organized areas of the callus. Embryoids show a bipolar organization with a shoot‐coleorhiza (root) axis and have a coleoptile‐like structure surrounded at the base by a cup‐shaped structure that resembles the scutellum in texture and morphology. Embryoids show bilateral or radial symmetry and “germinate” in vitro to form plants that have been grown to maturity in soil. Similar embryogenic callus cultures have been produced from young inflorescence tissues of hybrid Pennisetum, a triploid sexually sterile hybrid of P. americanum x P. purpureum. Plants derived from these have also been transferred to soil. The regenerated plants showed normal chromosome numbers.
NONCONFIRMATION OF NODULATION IN ARTEMISIA LUDOVICIANA
Authors: WULLSTEIN L. H. , Harker Alan
Published: January 2018

Reports of nodulation and nitrogen fixation specifically associated with nodules or insect galls of Artemisia ludoviciana were not confirmed.
HYDROCARBONS FROM PEDILANTHUS MACROCARPUS (EUPHORBIACEAE) OF BAJA CALIFORNIA AND SONORA, MEXICO
Authors: Sternburg Charles , Rodriguez Eloy
Published: January 2018

Pedilanthus macrocarpus (Euphorbiaceae) from Baja California and Sonora, Mexico is a desert xerophyte rich in polyisoprenes and other highly reduced hydrocarbons. The latex was analyzed for rubber content and found to contain 6–10% rubber by fresh weight. Four geographically distinct populations were analyzed for alkane content and the normal alkane range was shown to be C27H36 to C35H72. The different populations show significant quantitative and qualitative variation in their alkane content. Phytochemical findings suggest that the hydrocarbon chemistry can be useful in understanding the evolution of Pedilanthus macrocarpus in Baja California.
EFFECTS OF LIGHT ON ROOT GROWTH, NODULATION, AND APOGEOTROPISM OF ZAMIA PUMILA L. SEEDLINGS IN STERILE CULTURE
Authors: Webb David
Published: January 2018

Secondary root nodulation and apogeotropism of Zamia pumila L. seedlings grown axenically on modified White's minerals with 2% sucrose at pH 5.7 was caused by light. Light also inhibited primary and secondary root elongation as well as secondary root production. Light‐induced growth inhibition and nodulation were greatest at high light intensities. Apogeotropism was more frequent at low light intensities.
LEACHIELLA PACIFICA, GEN. ET SP. NOV., A NEW PARASITIC RED ALGA FROM WASHINGTON AND CALIFORNIA
Authors: Kugrens Paul
Published: January 2018

Leachiella pacifica, gen. et sp. nov., a marine alloparasitic red alga is described from Washington and California. Several species of Polysiphonia and Pterosiphonia are hosts for this parasite. The thallus is a white, multiaxial, unbranched pustule with rhizoidal filaments that ramify between host cells, forming numerous secondary pit connections with host cells. All reproductive structures develop from outer cortical cells. Tetrasporocytes, situated on stalk cells, undergo simultaneous, tetrahedral cleavage to form tetraspores. Spermatia are formed continuously by oblique cleavages of the elongate spermatial generating cells. This results in spermatial clusters consisting of 4–8 spermatia in an alternate arrangement. Carposporophyte development is procarpial. The carpogonium is part of a six‐celled branch including a sterile cell that is formed by the basal cell. The carpogonial branch is attached laterally to an obovate supporting cell that also forms an auxiliary cell, presumably formed prior to fertilization. After fertilization the carpogonium temporarily fuses with the auxiliary cell apparently to transfer the diploid nucleus and initiate further fusion with the subtending supporting cell to form an incipient fusion cell. The auxiliary cell portion of this fusion cell divides to form gonimoblast initials that continue to divide, forming gonimoblast filaments whose terminal cells differentiate into carpospores. The remainder of the fusion cell enlarges by continual fusion with adjacent vegetative cells. The resultant carposporophyte consists of a basal, multinucleate fusion cell supporting a hemispherical cluster of gonimoblast filaments with terminally borne carpospores. Vegetatively, Leachiella resembles several other parasitic red algae but it is clearly separated by the procarp, carposporophyte development and structure, and tetrasporocyte cleavage.
INITIATION OF STAMENS, CARPELS, AND RECEPTACLE IN THE CACTACEAE
Authors: Ross Robert
Published: January 2018

Five taxa representing the three tribes of the Cactaceae have similar patterns of stamen and carpel initiation but display differences in early receptacle development. The first ring of stamens and the carpels arise simultaneously from subsurface layers. The bases of carpels are congenitally connate. Additional stamens are initiated centrifugally. The shape of the floral meristem within the ring created by the first stamens varies. In Pereskia corrugata it remains broadly convex; in Opuntia engelmannii it forms a depression with a small convex central region; in Epiphyllum strictum it forms a broad shallow depression; in Echinocereus reichenbachii var. albispinus it develops a deep depression; and in Mammillaria compressa it develops a depression prior to stamen and carpel initiation. Changes in receptacle shape result from cessation of apical growth and activation of an intercalary ring meristem. These two processes occur earlier in ontogeny in the more advanced of these five taxa.
FLORAL ONTOGENY IN CYCLAMEN PERSICUM ‘F‐1 ROSEMUNDE ROSE’ (PRIMULACEAE)
Authors: Sundberg M. D.
Published: January 2018

Floral ontogeny was examined in Cyclamen persicum ‘F‐1 Rosemunde Rose’ using a combination of light and scanning electron microscopy. The leaf plastochron index (LPI), earlier calculated for leaf elongation, was used to determine the length of each stage of floral development. LPI will provide a useful tool for selecting flowers of a given stage from large plant populations or from plants where flowers are small or inaccessible during early ontogenetic stages. Most features of floral development are similar to those previously described for other primulaceous genera. The petal‐stamen relationship, however, is unusual; stamens arise through periclinal cell divisions in the adaxial surface layers of common petal‐stamen primordia. Anatomical evidence suggests that the placenta is formed both by appendicular initials which give rise to the ovules and ventral carpellary bundles, and receptacular cells which form some, if not all, of the central axis.
SYSTEMATIC SIGNIFICANCE OF POLLEN NUCLEAR NUMBER IN EUPHORBIACEAE, TRIBE EUPHORBIEAE
Authors: Webster Grady L. , Rupert Earlene , Koutnik Daryl
Published: January 2018

Pollen nuclear number is determined in 139 species of 5 genera in the Euphorbieae, subtribe Euphorbiinae. The 111 new determinations are tabulated along with previous reports, and the results indicate that the distribution of binucleate (II) and trinucleate (III) pollen is strongly associated with the taxonomic groupings within the Euphorbieae. Although binucleate pollen is probably primitive within the tribe Euphorbieae, as suggested by the nuclear condition in Neoguillauminia, the situation in Euphorbia still requires further elucidation. Within Euphorbia, the morphologically most primitive species studied have III pollen despite the fact that II pollen is presumably the original condition for the subtribe Euphorbiinae. In Euphorbia, II pollen only is reported from nine sections and III pollen only from ten sections, while in four sections (Esula, Goniostema, Aphyllis, and Deuterocalli) both II and III pollen have been found. The New World species of Euphorbia nearly all have III pollen, whereas the vast majority of the African succulents have II pollen. The genera of New World origin, Chamaesyce and Pedilanthus, have III pollen, while the African genera Monadenium and Synadenium have II pollen. Independent derivations of III pollen from II pollen appear to have occurred in sections Goniostema, Aphyllis, and Deuterocalli (all of subg. Euphorbia). There is no evidence that reversals from III to II pollen have occurred.
EMBRYOLOGICAL STUDIES IN THE FAMILY SAXIFRAGACEAE (S.L.). I. DEVELOPMENT OF THE OVULE AND EMBRYO SAC IN SAXIFRAGA FORTUNEI VAR. PARTITA (MAKINO) NAKAI
Authors: Abe Kiyohiko
Published: January 2018

The development of the ovule, megaspore and megagametophyte in Saxifraga fortunei var. partita (Makino) Nakai was observed. The ovule is anatropous, bitegmic, and crassinucellate. Both integuments originate from the epidermis. The archesporium is considered to be multicellular. The primary sporogenous cell functions as the megaspore mother cell which forms a T‐shaped tetrad. The chalazal member of the megaspore tetrad is functional and develops into a Polygonum‐type embryo sac. In the pyriform synergids the filiform apparatus is observed, but any hook or indentations could not be recognized. The antipodal cells are detectable until the Helobial endosperm undergoes several nuclear divisions. Secondary multiplication of the nuclei or the cells of the antipodals could not be observed.
DEVELOPMENT OF THE PERITHECIUM IN GNOMONIA COMARI (DIAPORTHACEAE)
Authors: Huang L. H. , Luttrell E. S.
Published: January 2018

Perithecia of Gnomonia comari (Ascomycetes) mature within 14 days on cornmeal agar under continuous fluorescent light at 25 C. The perithecium is initiated by a coiled, multicellular ascogonium. Branches from somatic hyphae surround the ascogonium. This hyphal envelope early differentiates into two regions: a centrum of pseudoparenchymatous cells and a peripheral wall of more elongated, flattened cells. The wall produces a long, ostiolate beak by eruption of a column of hyphae from the inner layers at the apex; the cells gradually become thick‐walled and brown from the peripheral layers inward. Proliferations from the ascogonial cells near the center of the perithecium form a bowl‐shaped mass of ascogenous hyphae which expands centrifugally until it appears in section as a crescentic layer across the middle of the centrum. The centrum pseudoparenchyma above this incipient hymenium disintegrates, and short abortive paraphyses extend upward from the subhymenial pseudoparenchyma into the resulting cavity. The paraphyses disintegrate as the asci develop among them. The hymenium gradually pushes downward into the disintegrating subhymenial pseudoparenchyma until it rests on the perithecial wall. Maturing asci become detached from the hymenium, fill the perithecial cavity, and pass through the ostiole. At the tip of the beak they discharge their ascospores forcibly. Diaporthaceae with abortive paraphyses may occupy an intermediate position in a series leading from forms (Gaeumannomyces graminis) with long delicate paraphyses resembling those in the Sordariaceae to forms (Stegophora ulmea) in which the centrum is entirely pseudoparenchymatous.
XYLARY UNION BETWEEN THE NEW SHOOT AND OLD STEM DURING TERMINAL BUD BREAK IN POPULUS DELTOIDES
Authors: Goffinet Martin C. , Larson Philip R.
Published: January 2018

Bursting terminal buds and subtending stems of Populus deltoides Bartr. ex Marsh. plants were examined at several stages to determine the pattern of xylary union between the 1st‐ and 2nd‐yr growth increments. Metaxylem vessels differentiated first in traces serving the basalmost leaf in the bud. As successively younger leaves began growth, metaxylem vessels differentiated in their traces. The site of metaxylem reactivation was in the second or third internode beneath the bud (i.e., in the 1st‐yr stem), and subsequent differentiation progressed bidirectionally in each set of traces as the leaves they served expanded. Traces leading either to abscised leaf positions on the 1st‐yr stem or to bud‐scale leaf positions were reactivated by the tangential “spread” of activity from adjacent traces serving expanding leaves. The new elements were all secondary xylem vessels, as were those of the basipetal trace components, although they were functionally continuous with the metaxylem vessels that differentiated acropetally. Xylem fibers were initiated in the same position and differentiated in the same sequence as vessels. However, fiber differentiation lagged behind that of vessels. Whereas vessel differentiation was associated with leaf expansion, fiber differentiation was associated with leaf maturation. As each leaf matured in sequence, the primary‐secondary transition zone advanced acropetally to the bud base and then in the new shoot until it attained a positional relation with leaf maturation comparable to that of 1st‐yr plants.
STEM ANATOMY OF PARTHENIUM ARGENTATUM, P. INCANUM AND THEIR NATURAL HYBRIDS
Authors: Mehta Indira J.
Published: January 2018

Guayule (Parthenium argentatum Gray) contains rubber in the parenchymatous cells of stems and roots. Stem anatomy of P. argentatum is described along with that of P. incanum H.B.K. (mariola). Anatomy of these species differs significantly. Phloem rays in both species increase in width by cell division and expansion; however, the increase observed in mariola is less as compared to that in guayule. Axial xylem parenchyma in guayule is generally a two‐cell strand as compared to the fusiform axial xylem parenchyma observed in mariola. Vascular ray cells and cells of the pith region of guayule are parenchymatous, whereas those of mariola are sclerenchymatous. As a result of introgression between guayule and mariola, three forms of guayule exist in the native stands of Mexico. Morphological differences between these guayule plants have been described previously. The stem anatomy of these three groups of plants differ importantly. Group I guayule plants, least introgressed by mariola, have taller rays with the cells of pith region and vascular rays parenchymatous. Group III plants, highly introgressed by mariola, have a few to many cells of vascular rays and pith with lignified secondary walls and shorter rays. Many of the anatomical characteristics of group II plants, somewhat introgressed by mariola, are intermediate between group I and III plants.
SPACING OF PARENCHYMA BANDS IN WOOD OF CARYA GLABRA (MILL.) SWEET, PIGNUT HICKORY, AS AN INDICATOR OF GROWTH RATE AND CLIMATIC FACTORS
Authors: Hill Jane F.
Published: January 2018

Variations in the spacing of concentric, tangential bands of apotracheal axial wood parenchyma cells in the annual growth rings of Carya glabra (Mill.) Sweet constitute a record of changes in radial growth rate and of fluctuations in climatic factors. This relationship was determined from trees that were growing under moisture stress and consequently had highly consistent ring‐width patterns from tree to tree. Band spacing decreased across a growth ring and was generally greater in wide than in narrow rings. Thus, the proportion of xylem cross‐sectional area occupied by axial parenchyma tissue was inversely related to ring width. Average numbers of bands in each of 67 years were analyzed relative to ring widths. Years in which bands were unusually numerous relative to ring width were years of low April‐May precipitation, leading to slow spring growth and closely spaced bands early in the growing season. Years in which band numbers were unusually low relative to ring width were years of high April‐May precipitation, leading to rapid growth and widely spaced bands early in the season; low July precipitation in these years apparently curtailed growth before much of the typical late‐season wood, with its closely spaced bands, could form. Parenchyma bands were aggregated within some rings, suggesting that a slowing of growth had been followed by a growth spurt. Evidence for a late‐season spurt was that rings with aggregations were significantly wider than rings formed the same year and not having aggregations of bands. The number of vessels per unit of cross‐sectional area was inversely related to ring width.
FOLIAR ONTOGENY AND HISTOGENESIS IN MAGNOLIA GRANDIFLORA L. I. APICAL ORGANIZATION AND EARLY DEVELOPMENT
Authors: Poster Michael T. , Tucker Shirley C.
Published: January 2018

Foliar ontogeny of Magnolia grandiflora was studied to elucidate possible unique features of evergreen leaves and their development. The apex of Magnolia grandiflora is composed of a biseriate or triseriate tunica overlying a central initial zone, a peripheral zone and a pith rib meristem. Leaf primordia are initiated by periclinal divisions on the apical flank of the tunica in its second layer. This initiation and expansion is seasonal just as in related deciduous magnolias. Following leaf initiation, a foliar buttress is formed and the leaf base gradually extends around the apex. As growth continues, separation of the leaf blade primordium from the stipule proceeds by intensified anticlinal divisions in the surface and subsurface layers near the base. Marginal growth begins in the blade primordium when it reaches approximately 200 μm in height and results in the formation of two wing‐like extensions, the lamina. This young blade remains in a conduplicately folded position next to the stipule until bud break.
EVOLUTIONARY IMPLICATIONS OF LEAF RESIN POCKET PATTERNS IN THE TROPICAL TREE HYMENAEA (CAESALPINIOIDEAE: LEGUMINOSAE)
Authors: Langenheim Jean H. , Lincoln David E. , Stubblebine W. H. , Gabrielli A. C.
Published: January 2018

ABSTRACT: Measurement of the size (volume), distribution, and density of resin pockets are compared in margin and center areas of leaves in 11 species (including six varieties of two widespread species) of Hymenaea. Resin composition and yield (mg/g leaf tissue) were analyzed by gas‐liquid chromatography. Resin pocket patterns in certain species are highly distinctive; also a relationship seems to exist between patterns of closely related species, with variation having occurred in species or populations of widespread species which have radiated into different kinds of habitats. Thus these patterns may provide useful taxonomic characters, but we suggest that some of the patterns (and thus composition and yield of resin of different portions of the leaf) have evolved under selective pressures of herbivorous insects.
ULTRASTRUCTURAL CHANGES OF MEMBRANES WITH HYDRATION IN SOYBEAN SEEDS
Authors: Chabot Jean Fincher , Leopold A. Carl
Published: January 2018

Structural changes of soybean seeds at various levels of hydration were examined for possible explanations of the rapid initial leakage of solutes during imbibition. A clustering of vesicles and lipid bodies was observed along the two types of membranes which must undergo most extensive enlargement: the plasmalemma and the protein bodies. There was no such association with the membranes of nuclei, plastids, and mitochondria. Freeze fracture replicas of tissue with less than about 18% water content yielded only small areas identifiable as plasma membrane and these contained many irregularities or pock marks. As imbibition proceeded, larger expanses of plasma membrane were revealed. The increase in water content was seen to remove the irregularities of the membrane plane, and generally was associated with an extensive increase in particles embedded in the membrane sheets. It is suggested that imbibition may involve rapid and extensive incorporation of new materials into expanding membranes of the cell, including addition of lipids and possibly of proteins.
PHENOTYPIC PLASTICITY OF BRANCHING PATTERN IN SUGAR MAPLE (ACER SACCHARUM)
Authors: Steingraeber David A.
Published: January 2018

Branching patterns of leader shoots and lower branches were compared in 15 sugar maple trees. The number of first‐order branches per second‐order branch (R1:2) differed very significantly between leader shoots and lower branches. Values of R1:2 averaged 6.47 for leaders and 4.06 for lower branches. Stepwise bifurcation ratios between successive higher orders did not differ significantly. The difference in R1:2 between leader shoots and lower branches within individual trees is the result of developmental‐phenotypic interactions, such that the number of leaf‐bearing shoots per support shoot decreases over time. These results indicate that branching patterns within individual trees are not stationary, as has commonly been claimed.
WHAT IS THE VASCULAR ARCHITECTURE OF COMPLEX MEDULLOSAN POLLEN ORGANS?
Authors: Rothwell Gar W. , Eggert Donald A.
Published: January 2018

The recent emphasis on vascular architecture as a key to interpreting the structure and phylogeny of Dolerotheca and similar pollen organs prompts a critical examination of this feature in specimens from the Upper Pennsylvanian of Illinois. Contrary to previous descriptions, the major bundle system of these organs consists of anastomosing strands that are not consistently positioned proximal to (over) radiating sclerenchymatous plates of ground tissue. In addition, branching that has been previously described as pinnate actually consists of nonpinnate divisions.
AUTOTRIPLOID AND AUTOTETRAPLOID CYTOGENETIC ANALYSES: CORRECTION COEFFICIENTS FOR PROPOSED BINOMIAL MODELS
Authors: Jackson R. C. , Hauber Donald P.
Published: January 2018

Correction coefficients have been derived for two‐chiasmata models of autotriploids and autotetraploids to correct meiotic configuration frequencies obtained from the binomial method when the P values are 0.5. In addition, equations are derived for the direct calculation of meiotic configuration frequencies in autotriploids of the two‐chiasmata model when P values are 0.5.
A NEW SPECIES OF ZOSTEROPHYLLUM FROM THE EARLY DEVONIAN OF NEW BRUNSWICK
Authors: Gensel Patricia G.
Published: January 2018

A new species of Zosterophyllum, Z. divaricatum Gensel, is described from the late Early Devonian (Emsian) of northern New Brunswick, Canada. It is a Platyzosterophyllum type, consisting of slender sometimes bifurcating axes with laterally borne sporangia oriented to one side of the axis. The species is distinctive in that axes bifurcate within fertile regions and in sporangium shape and attachment. Aspects of the morphology of axis and sporangium cuticle, tracheids, and spores are presented and considered in relation to comparable features in other Zosterophyllum species. Associated vegetative axes exhibiting H‐ and K‐branching patterns and also cuticular features similar to the fertile specimens are described and it is suggested that they may represent parts of the same plant. Zosterophyllum divaricatum is most similar to Z. llanoveranum, Z. fertile, and Z. spectabile, and also resembles Rebuchia ovata to some extent. Z. divaricatum offers considerable information on variation within one species concerning sporangium shape, attachment, and distribution and expands the known diversity of Platyzosterophyllum types.
IN VITRO ALLELOPATHIC INHIBITION OF NITRIFICATION BY BALSAM POPLAR AND BALSAM FIR
Authors: Thibault J.‐Robert , Fortin J.‐Andre , Smirnoff Wladimir A.
Published: January 2018

A soil percolation apparatus was used to study the effect of plant extracts on nitrification. Foliar leachates, leaf extracts, and bud extracts of balsam fir (Abies balsamea) and balsam poplar (Populus balsamifera) were added to the ammonium percolation solution. Color tests and quantitative measurement of residual ammonium and formed nitrate were applied.

Foliar leachates of balsam fir strongly inhibited nitrification; leachates of balsam poplar were slightly less inhibitory. Balsam fir needle and balsam poplar dormant bud extracts (5% w/v) completely prevented the oxidation of ammonium. The same estracts (2% w/v) still prevented the oxidation of ammonium to nitrate to a large extent. Once again balsam fir extracts inhibited the process more strongly than balsam poplar. No evidence was obtained for the presence of a specific inhibitor of nitrifier microorganisms.
QUANTITATIVE ANALYSIS OF VEGETATION AT THE RICHVALE VERNAL POOLS, CALIFORNIA
Authors: Schlising Robert A. , Sanders Ellen L.
Published: January 2018

California vernal pools exhibit vegetation of mainly native, annual vascular plants that flower and set seed as standing water from the Mediterranean climate wet season evaporates. Deeper depressions often show concentric rings of color from the different species responding to progressive drying of the habitat. Vernal pool plant life was numerically analyzed in 1979 near Richvale, in the Sacramento Valley, by sampling in a regular grid pattern that covered both the pool and the adjacent annual grassland. Each species was measured once in all sample sites, all data were pooled and an importance value was determined for each of the 61 species. Species are discussed in relation to the high water line of a pool (maximum extent of standing water). Samples covering all regions of a plot showed there are “pool species” (e.g., Lasthenia fremontii) with nearly identical distributions almost totally within high water line. Four native species made up 75% of all the plants counted in the pool samples. In general, pool species had higher densities inside the high water line than the “non‐pool species” had outside the high‐water line. Non‐pool species (e.g., Aira caryophyllea) tended to occur in the pool samples more than the pool species occurred outside the pool. Some species (e.g., Limnanthes alba) had roughly similar absolute and importance values for pool and non‐pool areas; these were called “transition species,” and had less importance than either pool or non‐pool species throughout the plots. The two study plots, 40 m apart, had similar rankings for the top pool, non‐pool and transition species: importance of the species varied within each of these two neighboring pools.
INFLORESCENCE AND FLOWER DEVELOPMENT IN THE PIPERACEAE. II. INFLORESCENCE DEVELOPMENT OF PIPER
Authors: Tucker Shirley C.
Published: January 2018

The inflorescence development of three species of Piper (P. aduncum, P. amalago, and P. marginatum), representing Sections Artanthe and Ottonia, was studied. The spicate inflorescences contain hundreds or even thousands of flowers, depending on the species. Each flower has a tricarpellate syncarpous gynoecium and 4 to 6 free stamens, in the species studied. No sepals or petals are present. In P. marginatum the apical meristem of the inflorescence is zonate in configuration and is unusually elongate: up to 1,170 μm high and up to 480 μm wide during the most active period of organogenesis. Toward the time of apical cessation both height and diameter gradually diminish, leaving an apical residuum which may become an attenuate spine or may be cut off by an abscission zone just below the meristem. The active apex produces bract primordia; when each is 40–55 μm high, a floral apex is initiated in its axil. Both bract and floral apex are initiated by periclinal divisions in cells of the subsurface layer. The bracts undergo differentiation rather early, while the floral apices are still developing. The last‐produced bracts near the tip of the inflorescence tend to be sterile.
SEASONAL AND INDIVIDUAL VARIATION IN LEAF QUALITY OF TWO NORTHERN HARDWOODS TREE SPECIES
Authors: Schultz Jack C. , Nothnagle Philip J. , Baldwin Ian T.
Published: January 2018

Seasonal trends in five traits of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula allegheniensis Britt.) leaves thought to influence feeding by herbivores were measured from 17 May through 19 September, 1979. Total nitrogen and water contents declined and toughness increased through the growth season. These seasonal changes were more pronounced in sugar maple than in yellow birch. Total polyphenol contents and tanning coefficients of leaf extracts from both species reached a season high by the end of May and changed very little after that date; these patterns differ from those reported by several other investigators. Sugar maple leaf extracts exhibited much higher tanning coefficients than did those of yellow birch, a finding which is consistent with current plant defense theory. Significant differences in total polyphenol content and tanning coefficients were found between individual trees in yellow birch, but not sugar maple. The relationship between successional status, leaf quality traits, and variability in these traits in forest trees is discussed.
CHANGES IN MITOTIC ACTIVITY AND CELL SIZE IN THE APICAL MERISTEM OF HELIANTHUS ANNUUS L. DURING THE TRANSITION TO FLOWERING
Authors: Marc Jan , Palmer John H.
Published: January 2018

Cellular changes in the shoot apical meristem of Helianthus annuus L. have been investigated in relation to its progress towards flowering. During the strictly vegetative phase, lasting for 6–7 days from sowing, mitotic divisions were confined to the peripheral zone, while the central mother cells zone proper, together with the distal cells positioned above the mother zone and also the central portion of the tunica, were relatively quiescent. Mitotic activity increased in the distal cells zone on day 8 and reached the level of that in the peripheral zone by day 12. This was accompanied by an enlargement of this zone and the consequent recession of the mother zone away from the central tunica. At the same time there was a substantial increase in the amount of cytoplasm in the cells of the central tunica. Mitotic activity in the central tunica began on day 12 and reached a peak on day 16. This zone then lost its distinct entity and was replaced by a uniform dome‐shaped meristematic layer that became apparent by day 16. The cells of the mother zone remained quiescent during the transition period.
TWO NEW MEMBERS OF THE BLASTOCLADIACEAE. II. MORPHOGENETIC RESPONSES TO O2 AND CO2
Authors: Robertson Jack A. , Emerson Ralph
Published: January 2018

The development of Microallomyces dendroideus and Allomyces reticulatus was studied under various mixtures of O2, CO2 and N2. All thalli grown in broth or agar media in air produce abundant resistant sporangia but rarely produce any zoosporangia. In both fungi, the proportion of zoosporangia borne by the thalli increases as the oxygen level decreases. In addition, increased CO2 strongly stimulates resistant sporangium germination in M. dendroideus. Neither fungus grows in the absence of oxygen; therefore, they seem to be adapted for rapid multiplication in a microaerophilic niche.
ELEMENTAL ANALYSIS OF DEPOSITS ON THE ROOTS OF SPARTINA ALTERNIFLORA LOISEL.
Authors: Mendelssohn Irving A. , Postek Michael T.
Published: January 2018

Spartina alterniflora, salt marsh cordgrass, is the dominant angiosperm of a large majority of regularly flooded marshes of the Atlantic and Gulf coasts of the United States. In Louisiana, this species often occurs in two distinct zones: a more productive streamside site (adjacent to tidal creeks), and a less productive and sparsely populated inland area. Reddish‐brown deposits are present on the roots of streamside Spartina and visually absent from the roots of inland plants. A study of streamside roots using scanning electron microscope and energy dispersive X‐ray microanalysis demonstrated that the coatings are restricted to the outer cell wall of the epidermis and are composed primarily of iron. Roots of inland plants have minor iron deposits. Citrate‐dithionite extraction of the coatings and subsequent atomic absorption spectrophotometric analysis confirmed these deposits to be iron, although some manganese was present. Approximately 50 times more iron was found on streamside roots compared to roots from inland plants. These results indicate a better developed oxidized rhizosphere associated with streamside Spartina roots than the inland and, hence, the potential for a more favorable environment in which nutrient uptake may proceed.
OVULE ABORTION IN ‘NONPAREIL’ ALMOND (PRUNUS DULCIS [MILL.] D. A. WEBB)
Authors: Pimienta Eulogio , Polito Vito S.
Published: January 2018

The earliest indication of ovule abortion in almond (Prunus dulcis [Mill.] D. A. Webb ‘Nonpareil‘) is the deposition of callose (as indicated by aniline blue fluorescence) 2 days after pollination which is 2 days before clear histological symptoms of ovule degeneration are evident and 6 days before fertilization of the viable ovule. Callose deposition begins in the chalazal region of the nucellus where the funicular trace enters the ovule and ramifies into the integuments. As ovule abortion progresses, callose deposition in the inner integument extends as a ring around the nucellus. Movement of the fluorescent dye disodium fluorescein (uranin) indicated that translocation from the vascular trace into abortive ovules becomes blocked at the chalazal position. The dye freely penetrates and diffuses into viable ovules but fails to penetrate abortive ovules. Lack of, or delayed and irregular, megagametophyte development was another characteristic of abortive ovules. Biochemical and histochemical analyses of abortive and viable ovules indicated that carbohydrate depletion parallels ovule abortion. These observations lead to the conclusion that ovule abortion is accompanied by blockage in metabolite supply although whether this blockage is the primary cause or a consequence of ovule abortion is uncertain.
ANATOMY OF THE PRIMARY PHLOEM FIBER SYSTEM IN PISUM SATIVUM
Authors: Aloni Roni , Gad Alexander E.
Published: January 2018

Unusual structure of the primary phloem fiber system in the stem of Pisum sativum is described. The five lowest internodes contain large fiber strands that split radially and may also split tangentially. In both the stem and the root the number of fibers along a strand decreases with the distance below the leaf; in contrast, fiber length increases. Fiber dimensions are also increased in the centripetal direction.
POLLEN MORPHOLOGY AND THE RELATIONSHIPS OF CIRCAEASTER, OF KINGDONIA, AND OF SARGENTODOXA TO THE RANUNCULALES
Authors: Nowicke Joan W. , Skvarla John J.
Published: January 2018

The pollen of three monotypic genera, Circaeaster, Kingdonia, and Sargentodoxa has been examined by light and scanning electron microscopy and in the case of the last genus, also by transmission electron microscopy. The type of tectum found in Circaeaster and Kingdonia, derivations of a compound layer of striae, has a restricted distribution in the Order Ranunculales. Of 64 genera examined in this order only six had species with a similar tectum. They include Achlys, Epimedium, Jeffersonia, and Vancouveria of the Berberidaceae s.l., the controversial Hydrastis, and Trollius of the Ranunculaceae. Circaeaster and Kingdonia have been considered as related since both have rare and primitive vegetative characteristics, the most notable being open dichotomous leaf venation. They are probably best treated as a ditypic family, Circaeasteraceae. The pollen of Sargentodoxa, especially the structure of the exine, closely resembles that of the Lardizabalaceae. However, the fruits of Sargentodoxa have been considered to be distinct from those of the Lardizabalaceae, suggesting that it be treated as a separate, but closely allied, family.