bluuebunny/crossref_metadata_2025 huggingface dataset:
ORCHID MYCORRHIZA: VITAMIN PRODUCTION AND REQUIREMENTS BY THE SYMBIONTS
Authors: Hijner J. A. , Arditti Joseph
Published: January 2018

A Rhizoctonia species isolated from Cymbidium has been cultured successfully on a defined medium consisting of minerals, sugar, thiamine, and folic acid. Thiamine can be replaced by its thiazole component, which is probably produced by germinating orchids. The fungus apparently produces the pyrimidine moiety of thiamine, a compound which may enhance growth of certain orchid seedlings. Niacin is also provided by the fungus. Para‐aminobenzoic acid, a constituent of folic acid, produced and released by orchid seeds, can satisfy the vitamin requirement of the fungus. These findings point to the possibility that orchids and their fungi may have coevolved with respect to vitamin requirements. The data also suggest that exchanges of vitamins or their components between orchids and endophytes are important aspects of the symbiotic relationship.
MACHAERANTHERA RESTIFORMIS (ASTERACEAE) A BIZARRE NEW GYPSOPHILE FROM NORTHCENTRAL MEXICO
Authors: Turner B. L.
Published: January 2018

A rayless, diploid (n = 4), shrubby, new species of Machaeranthera is described from gypsum dunes near Cuatro Ciénegas, Coahuila. It is most closely related to M. johnstonii, another rayless, shrubby, endemic gypsophile of this region. Machaeranthera restiformis often occurs with the wide‐ranging, white‐rayed species, M. gypsophila (n = 4) with which it occasionally hybridizes.
ONTOGENY OF THE PRIMARY THICKENING MERISTEM IN SEEDLINGS OF BOUGAINVILLEA SPECTABILIS
Authors: Stevenson Dennis W. , Popham Richard A.
Published: January 2018

Anomalous secondary thickening occurs in the main axis of Bougainvillea spectabilis as a result of a primary thickening meristem which differentiates in pericycle. The primary thickening meristem first appears in the base of the primary root about 6 days after germination and differentiates acropetally as the root elongates. It begins differentiating from the base of the hypocotyl toward the shoot apex about 33 days after germination. The primary thickening meristem is first observable at the base of the first internode about 60 days after germination. It then becomes a cylinder in the main axis of the seedling. No stelar cambial cylinder forms in the primary root, hypocotyl, or stem because vascular cambium differentiation occurs neither in the pericycle opposite xylem points in the primary root nor in interfascicular parenchyma in the hypocotyl or stem. The primary vascular system of the stem appears anomalous because an inner and an outer ring of vascular bundles differentiate in the stele. Bundles of the inner ring anastomose in internodes, whereas those of the outer ring do not. Desmogen strands each of which is composed of phloem, xylem with both tracheids and vessels, and a desmogic cambium, differentiate from prodesmogen strands in conjunctive tissue. The parenchymatous cells surrounding desmogen strands then differentiate into elongated simple‐pitted fibers and thick‐walled fusiform cells that are about the same length as the primary thickening meristem initials.
CLASSIFICATION OF THE ARCHITECTURE OF DICOTYLEDONOUS LEAVES
Authors: Hickey Leo J.
Published: January 2018

A classification of the architectural features of dicot leaves—i.e., the placement and form of those elements constituting the outward expression of leaf structure, including shape, marginal configuration, venation, and gland position—has been developed as the result of an extensive survey of both living and fossil leaves. This system partially incorporates modifications of two earlier classifications: that of Turrill for leaf shape and that of Von Ettingshausen for venation pattern. After categorization of such features as shape of the whole leaf and of the apex and base, leaves are separated into a number of classes depending on the course of their principal venation. Identification of order of venation, which is fundamental to the application of the classification, is determined by size of a vein at its point of origin and to a lesser extent by its behavior in relation to that of other orders. The classification concludes by describing features of the areoles, i.e., the smallest areas of leaf tissue surrounded by veins which form a contiguous field over most of the leaf. Because most taxa of dicots possess consistent patterns of leaf architecture, this rigorous method of describing the features of leaves is of immediate usefulness in both modern and fossil taxonomic studies. In addition, as a result of this method, it is anticipated that leaves will play an increasingly important part in phylogenetic and ecological studies.
THE IN VITRO SECRETION OF GROWTH REGULATORS BY ISOLATED CALLUS TISSUES
Authors: Lin Alan , Mathes Martin C.
Published: January 2018

Tissues from a wide variety of plants were surface sterilized, isolated, and grown on different media. These isolated tissues were bioassayed for growth regulatory activity. The secretions from four of the 20 callus tissues inhibited the growth of Bacillus subtilis. An aseptic method for measuring the growth of Lemna was developed and used to detect inhibitory materials in medium which had supported the growth of five isolated callus tissues. In the seed (Lycopersicon esculentum) germination test five callus tissues had an inhibitory influence while two callus tissues showed a stimulatory effect. The study also included expressed juices and extracts of callus tissues which secreted regulatory materials. The expressed juice of five callus tissues contained materials which inhibited the growth of Lemna. Two expressed juices inhibited the growth of Bacillus subtilis. The water extract of two callus tissues inhibited the growth of Lemna. Fifty percent of the plants which have been reported to produce growth regulatory materials in nature also produced callus tissue which was capable of regulating growth of assay organisms.
SOME HISTOCHEMICAL, ULTRASTRUCTURAL, AND NUTRITIONAL ASPECTS OF THE OVULE OF QUERCUS GAMBELII
Authors: Mogensen H. Lloyd
Published: January 2018

Histochemical analyses of the ovule of Quercus gambelii show that the major food reserves (starch grains and lipids) are located almost exclusively within the outer integument. Vascular traces are present only within this integument which contains numerous, well‐developed plasmodesmata. The inner integument is virtually devoid of any food reserves and has very few plasmodesmata. The ovule has a persistent chalazal extension of residual nucellar cells (called the postament) which projects into the embryo sac. Due to the above information and the fact that the synergids rarely contain starch and no plasmodesmata are present in the walls of any of the cells of the egg apparatus (Mogensen, 1972), it is concluded that the synergids play little or no role in embryo sac nutrition. Rather, it is proposed that the pathway of available food materials in the young ovule is from the outer integument to the chalaza and through the postament into the embryo sac.
RHIZOMORPHS IN SOIL NOT CONNECTED WITH FUNGAL FRUITING BODIES
Authors: Went F. W.
Published: January 2018

About half the root‐like structures found in the litter of a Pinus murrayana forest were found to be in reality rhizomorphs of fungi. Conclusions based on direct observations of the soil are reinforced with culture experiments with litter in the greenhouse. Microscopic studies show a distinct structure of these rhizomorphs which distinguishes them from roots. Covered with a tight network of hyphae, they have very wide hyphae in their centers, which are named tracheodes in this paper. Although fungal rhizomorphs are well known in connection with fruiting bodies of mushrooms, the rhizomorphs in montane forest and desert occur apart from fruiting bodies and thus far have not been connected with any known mushrooms.
DISC ELECTROPHORETIC STUDY OF POLLEN PROTEINS FROM NATURAL POPULATIONS OF BETULA POPULIFOLIA IN NEW JERSEY
Authors: Payne Richard C. , Fairbrothers David E.
Published: January 2018

Pollen proteins from individual trees of eight natural populations of B. populifolia Marsh. located in diverse physiographic provinces of New Jersey were separated by disc electrophoresis with 7 % acid and basic acrylamide gels. Specific stains and substrates for detecting general proteins, esterase, and leucine aminopeptidase isoenzymes were utilized. Average Rp values, 95 % confidence intervals, and percentage similarity values were calculated. Dendrograms were constructed to illustrate protein similarity among populations. The effects of increasing the concentration of protein samples subjected to electrophoresis and storage of pollen (4 C over 16 months) were investigated. After statistical analysis we concluded that: each protein system investigated revealed different amounts of intra‐ and interpopulation variation, different population ranking (determined by amount of variation), and different population similarity groupings; conclusions based on the comparisons of numbers of protein bands were not always valid; disc electrophoretic data revealed information about natural selection and gene flow; the effect of increasing pollen protein concentration was quantitative; with storage pollen proteins increased in overall positive charge.
MACROCYSTS IN THE LIFE CYCLE OF THE DICTYOSTELIACEAE. I. FORMATION OF THE MACROCYSTS
Authors: Nickerson Ann Weinkauff , Raper Kenneth B.
Published: January 2018

Macrocysts, a morphogenetic phase that is alternative to sorocarp formation in the life cycle of some cellular slime molds, are known for two genera and five species of the Dictyosteliaceae. In all of these macrocyst formation was found to be strongly affected by four factors: light, temperature, moisture, and the composition of the medium. In general, macrocyst formation was suppressed and sorocarp formation was enhanced by exposure to light, by incubation at temperatures lower than 20 C, by buffering nutrient media with phosphates, and by reducing atmospheric moisture through the use of clay covers on Petri dishes. The extent to which these environmental factors, singly or in combination, inhibited the production of macrocysts varied among the different strains and species.
VARIATIONS IN THE LEAF OILS OF THREE SPECIES OF JUNIPERUS
Authors: Tatro V. E. , Scora R. W. , Vasek F. C. , Kumamoto J.
Published: January 2018

Leaf oils from Juniperus occidentalis, J. osteosperma, and J. califomica were analyzed qualitatively and quantitatively for characteristic chemical composition. Seasonal, diurnal, and local microcline variation was quantified. Neither microcline nor seasonal variation appeared to have a significant effect on the leaf oil composition, although some variation was observed. A definite trend toward diurnal cycling was detected and tentatively linked to air temperature fluctuation from dawn to dark.
MACROCYSTS IN THE LIFE CYCLE OF THE DICTYOSTELIACEAE. II. GERMINATION OF THE MACROCYSTS
Authors: Nickerson Ann Weinkauff , Raper Kenneth B.
Published: January 2018

Macrocyst germination was demonstrated in the five species of the Dictyosteliaceae known to produce these structures. The morphological changes that occurred during germination appeared to be identical in all of the strains examined, showing the following stages: (1) swelling of the dark, contracted content of the dormant cysts, (2) gradual loss of color and reappearance of cells within what previously appeared as a homogeneous protoplasmic mass, and (3) rupture of the heavy cellulosic cyst wall to liberate the myxamoebae. The age of the macrocyst appeared to be the most critical factor in determining whether or not germination would occur, since the cysts in many of the strains needed to age for several weeks or months before germination could be demonstrated. In Dictyostelium mucoroides strain DM‐7, upon which the current study was centered, light was necessary to stimulate germination of young macrocysts—a requirement that gradually diminished as the cysts aged. The rate of germination and the temperature permitting germination were also age dependent: older macrocysts germinated more rapidly and at considerably higher temperatures than did young cysts. Although light was not essential for germination in every strain, the results obtained with strain DM‐7 seem to be generally applicable to the germination process.
FORMATION AND DISSOCIATION OF CELL AGGREGATES IN SUSPENSION CULTURES OF PAUL'S SCARLET ROSE
Authors: Wallner Stephen J. , Nevins Donald J.
Published: January 2018

In liquid culture stem tissue of Paul's Scarlet rose produces a suspension containing cell aggregates of extremely variable dimensions. There is, however, a definite pattern of change in the degree of cell aggregation over time. During the period of most rapid cell division large aggregates form as the result of a minimal separation of the proliferating cells. As the rate of cell division slows, the average number of cells per aggregate decreases. The dissociation of cell aggregates continues at a uniform rate after cell division has stopped. Cell separation is inhibited at low (0.1 mg/1) auxin (NAA) concentrations and by substitution of sucrose for glucose in the culture medium. Cell separation is delayed (but not greatly inhibited) by kinetin. The presence of casein hydrolysate prevents the formation of the large cell aggregates normally occurring in the early stages of the culture cycle. A variant strain which shows a much higher degree of cell separation has been isolated from stock callus tissue grown on solid medium.
PERITHECIAL DEVELOPMENT IN HYPOMYCES AURANTIUS
Authors: Samuels Gary J.
Published: January 2018

Perithecia of Hypomyces aurantius are initiated by solitary, symmetrical, hyphal coils. During development of the ascocarp, a locule forms concomitantly with centripetal paraphyses, the uppermost of which elongate downward as a palisade of narrow, septate filaments, the apical paraphyses. The initiating coil retains its integrity in the middle of the primordium and becomes the ascogenous system. Uninucleate, diploid cells are part of the ascogenous system. The ascogenous system proliferates through croziers from which asci develop. The haploid chromosome number is 4. The perithecial papillae are formed of spherical cells. This pattern of development is a modification of the Nectria‐type of development and characterizes the genus Hypomyces.
PHOTOPERIOD EVIDENCE IN THE INTRODUCTION OF XANTHIUM STRUMARIUM TO TAHITI AND HAWAII FROM MEXICO
Authors: McMillan Calvin
Published: January 2018

Successful invasion of islands in the Pacific by Xanthium probably resulted from the chance introduction of a morpho‐physiological form adapted to subtropical coastal habitats in North America. This hypothesis was tested by comparing naturalized plants from Tahiti in the Society Islands and Oahu in the Hawaiian Islands with collections from various coastal sites in Mexico. Plants from Tampico and Ciudad Mante, Tamaulipas; Veracruz (Antigua), Veracruz; and Salina Cruz, Oaxaca have morphological and physiological similarity to the Pacific introductions; however, each collection has certain niche relations that are slightly different from each other. All of the collections are in the same morphological complex and have apparent critical nights of 10.75–11 hr for reproduction. This morpho‐physiological form is probably indigenous to Mexico, and it is widely distributed on the northeastern coastal plain of Tamaulipas.
ONTOGENETIC STUDY OF FLORAL ORGANS OF PEACH (PRUNUS PERSICA) UTILIZING CYTOCHIMERAL PLANTS
Authors: Dermen Haig , Stewart R. N.
Published: January 2018

Cell lineages were followed throughout floral ontogeny in cytochimeral peaches [Prunus persica (L.) Batsch] by observations of chromosome number and nuclear size. The contribution of the three apical cell layers to the organs of the flowers was determined. In addition to the epidermal tissue, L‐I produced several layers of cells at the suture of the ovary wall, seven or eight cell layers of the nucellus at the micropylar end of the ovule, and almost all of the integuments. L‐II gave rise to extensive internal tissue in the calyx and corolla tubes and to all internal tissue of the petal, anther, and ovule except for a small region at the base of the latter two organs. L‐III contributed significantly only to the central region of the calyx and corolla tubes and the ovary wall. A single apical layer gave rise to several different tissues, and at times a single tissue was made up of cells from 1–3 different apical layers. Within the limits imposed by their genotype the final form of differentiated cells was determined by their position in the mature organ and not by the apical layer from which they were derived. The corolla tube was shown to be a single structure, congenitally fused, and the ovary to be ontogenetically fused at the suture.
VERBESINA SECTION XIMENESIA (COMPOSITAE): BIOSYSTEMATICS AND ADAPTIVE VARIATION
Authors: Coleman James R.
Published: January 2018

Section Ximenesia is native to the southwestern United States and northern Mexico. Two of its taxa, Verbesina encelioides subsp. exauriculata and V. nana, are more western and occur in arid or semiarid regions, whereas the third taxon, V. encelioides subsp. encelioides, is more eastern and occurs in relatively moist regions. A crossing program revealed the absence of isolating barriers between the subspecies of V. encelioides. It is suggested that V. encelioides and V. nana are effectively isolated genetically by differences in ploidy. The study of several morphological characters of both field‐collected and garden‐grown populations indicates that differential adaptation for aridity has been of primary importance in the evolution of section Ximenesia. The taxa occupying arid regions show a reduction of transpiring surface, reduced reproductive capacity, and reduced dispersibility.
SOLUBILITY OF POLLEN EXINES
Authors: Southworth Darlene
Published: January 2018

The sporopollenin of pollen exines ofAmbrosia trifidais soluble in fused potassium hydroxide, in strong oxidizing solutions, and in certain organic bases. It is insoluble in other organic and inorganic acids and bases, in lipid solvents, and in detergents. The outer exine layer of gymnosperm and angiosperm pollen dissolves in 2‐aminoethanol. The inner exine layer, as well as the exine of pteridophyte spores, is insoluble. The exine dissolution process in 2‐aminoethanol involves swelling and disintegration of exine structures, leaving some residual globules. Sporopollenin shares some solubility properties with lignin and cutin but appears to be chemically distinct from these substances.
MORPHOLOGY OF SOME MAIZE‐TRIPSACUM HYBRIDS
Authors: Newell C. A. , de Wet J. M. J.
Published: January 2018

Diploid (2n = 20) and tetraploid (2n = 40) Zea mays L. were crossed with diploid (2n = 36) and tetraploid (2n = 72) Tripsacum dactyloides (L.) L. to produce a series of hybrids combining different numbers of haploid genomes from each parent. Eight hybrid groups and three parental groups were studied morphologically. Twenty‐nine quantitative characters were recorded for each sample. Data were analyzed by univariate analysis of variance, multivariate analysis of variance, and discriminant function analysis, in an attempt to evaluate hybrid differences objectively and determine which morphological characters contribute statistically to group separation. The overall MANOVA F test was significant, establishing the presence of real differences between the hybrids; discriminant function analysis indicated that the percent of paired pistillate spikelets/cupule in the lateral inflorescence was the main variable which differentiated hybrids. Duncan's Multiple Range Tests for significant differences between means were applied to five variables contributing maximally to group discrimination, using the appropriate univariate ANOVAs. Pronounced maize‐like attributes of backcross hybrids, as compared with corresponding F1's possessing similar genome constitutions, gave possible evidence of gene transfer between Zea mays and Tripsacum during backcrossing to maize.
A GENERIC CONSPECTUS OF THE SUBTRIBE PERITYLINAE (ASTERACEAE‐HELENIEAE) AND REASSESSMENT OF ITS TRIBAL POSITION
Authors: Powell A. M. , Turner B. L.
Published: January 2018

The subtribe Peritylinae, long treated as an element of the polyphyletic, chaffless tribe Helenieae, is recognized as containing 7 or 8 genera (Perityle, Pericome, Correllia, Amauria, Eutetras, Oxypappus, Eatonella and possibly Hulsea). Using mainly morphological data and a phyletic perspective, we concluded that the Peritylinae is best treated as a subtribe within the Senecioneae, where it should be positioned with or near Crocidium and Bartlettia. Reasons for this disposition are discussed in some detail.
SCANNING ELECTRON MICROSCOPY AND ENERGY DISPERSIVE X‐RAY ANALYSIS OF CHALK SECRETING LEAF GLANDS OF OF PLUMBAGO CAPENSIS
Authors: Sakai William S.
Published: January 2018

Chalk secreting leaf glands of Plumbago capensis Thunb. were examined by polarized reflected light microscopy, scanning electron microscopy, x‐ray diffraction, and energy dispersive x‐ray analysis. There are about 23 glands per mm2 on the lower leaf surface and none on the upper surface. Each gland measures 20–30 μm in diam and consists of four small secretory cells surrounded by four subsidiary cells. Secretion of chalk is apparently through a pore in the surface of each secretory cell. The secreted material was crystalline and x‐ray diffraction confirmed the presence of two minerals: calcite (CaCO3) and nesquehonite (MgCO3 · 3H2O). Energy dispersive x‐ray analysis revealed the presence of magnesium, silicon, phosphorus, sulfur, chlorine, potassium, and calcium in the epidermal cells. However, only calcium and magnesium and traces of silicon were detected in the secreted material. A distribution analysis showed calcium and magnesium to be uniformly distributed through the secreted material.
POPULATION DIFFERENCES IN INDIGENOUS FUSARIUM SPECIES BY CORN CULTURE OF PRAIRIE SOIL
Authors: Windels Carol E. , Kommedahl Thor
Published: January 2018

Six species of Fusarium were identified among approximately 7,000 cultures isolated from roots and soils collected from prairies and cornfields in southern Minnesota. In both soil sources, F. oxysporum and F. solani predominated, followed in order by F. roseum, F. episphaeria, F. tricinctum, and F. moniliforme. The same order was obtained for the 28 species of prairie grasses and forbs as for corn. From prairie plant and corn roots, respectively, F. oxysporum was isolated from 64 and 90%; F. solani, 26 and 80%; F. roseum, 8 and 35%; and F. tricinctum, 6 % each. In 10 of 17 companion soil pairs, populations of Fusarium species were higher in cornfield than in prairie soils. Populations of F. roseum and F. moniliforme especially, were higher in cornfield soils of sample pairs, but populations of F. solani were higher in prairie soils. Fusarium roseum ‘Equiseti’ was the predominant cultivar of this species in both prairie and cornfield soils. Thus all six species of Fusarium appeared to be indigenous to the prairie, and some, especially F. roseum, apparently had increased in prevalence in soil and roots by corn culture.
PHYTOCHROME DISTRIBUTION IN ETIOLATED GRASS SEEDLINGS AS ASSAYED BY AN INDIRECT ANTIBODY‐LABELLING METHOD
Authors: Pratt Lee H. , Coleman Richard A.
Published: January 2018

The distribution of phytochrome in several etiolated grass seedlings (Avena saliva L., cvs. Garry and Newton; Secale cereale L., cv. Balbo; Hordeum vulgare L., cv. Harrison; Oryza sativa L; Zea mays L., cv. Golden Cross) was determined, by an indirect antibody‐labelling method employing peroxidase as the ultimate label. Although the pattern of phytochrome distribution in etiolated shoots varies widely, it is nevertheless clear that, with the exception of corn, in which phytochrome is relatively uniformly distributed, the distribution of phytochrome is highly specific with respect both to organs and to cell types within an organ for a given species. Oat, rye, barley, and rice shoots all have high concentrations of phytochrome near the tips of their coleoptiles, as well as near the shoot apex itself. Rice, barley, and rye also have high concentrations of phytochrome in their leaf bases, but oat leaves are almost totally devoid of measurable phytochrome. An association of phytochrome with vascular tissue often occurs and is most pronounced in the rice shoot. Dark‐grown roots were found to have high levels of phytochrome only in the root caps, with lesser amounts, if any, observed in other parts of the root.
ORGANOGRAPHY, BRANCHING, AND THE PROBLEM OF LEAF VERSUS BUD DIFFERENTIATION IN THE VINING EPIPHYTIC FERN GENUS MICROGRAMMA
Authors: Hirsch Ann M. , Kaplan Donald R.
Published: January 2018

Investigation of the development and organography of the shoot systems of Microgramma vacciniifolia and M. squamulosa was undertaken for the purpose of determining: (1) the features of shoot growth that are responsible for the distinctive vining character of these epiphytic ferns; and (2) the mode of origin of branches and their contrast with leaf initiation. Shoots of both species are dorsiventral and plagiotropic (i.e., parallel to the substrate) in habit. Since the shoot apical meristem is radial in transectional symmetry, shoot dorsiventrality in Microgramma is a postgenital or secondary developmental event, and its inception is related to the initiation of lateral appendages. Leaves and buds arise in a distichous phyllotaxis and occupy opposite and alternating positions on the dorsal surfaces and flanks of the rhizome. Endogenous roots are initiated in two rows from the ventral surface of the stem, in the vicinity of the rhizome meristem; however, they do not emerge from the rhizome until some distance behind the tip and do not elongate until the region of substrate contact. We conclude that the vining nature of this fern rhizome is a result of precocious internodal elongation and the concomitant delay of leaf and bud expansion in the region of stem elongation. In addition, observation of branch origin confirms previous suggestions that branching in Microgramma is strictly lateral and extra‐axillary and not a dichotomous derivative as proposed by some workers. Leaf and bud primordia differ not only in the nature of their respective vascular supplies but also in their actual course of initiation. In the case of the leaf, the primordium is precociously emergent and exhibits a lenticular apical cell at its summit when it is only one plastochron removed from the flanks of the apical meristem. By contrast, initials of the bud primordium divide less actively and remain in a sunken position for at least 5–6 plastochrons; only when the bud apex becomes expanded and emergent does a tetrahedral apical cell become recognizable at the tip of the bud promeristem. Because of the distinctive pattern of branch and leaf origin, as well as the lack of adventitious and phyllogenous origin of branch primordia, we suggest that the shoot of Microgramma is a useful test organism for the re‐examination of the problem of leaf and bud determination in the ferns.
DETERMINATION OF RHIZOID ORIENTATION BY LIGHT AND DARKNESS IN GERMINATING SPORES OF ONOCLEA SENSIBILIS
Authors: Miller John H. , Greany Robin H.
Published: January 2018

When spores of the fern, Onoclea sensibilis L., are allowed to germinate in darkness, the rhizoid and the protonema are positioned at close to a right angle. If the spores are exposed initially to light and allowed to germinate, the rhizoid and protonema are positioned nearly axially, at opposite ends of the spore. The greater the duration and intensity of the initial illumination, the greater the tendency towards axial arrangement. All colors of light are active to some degree, and the effects are intensity‐dependent. The response occurs in a uniform light field and is not dependent on a directional stimulus; the phenomenon reflects the relative arrangement of one part of the gametophyte to another part but not the orientation of growth with respect to an external stimulus. Direct tests show that neither the relative rhizoid orientation nor initial polarity of germination are affected by unilateral white light or polarized red light; the subsequent growth of the protonema, however, is oriented perpendicular to the plane of light polarization. The effects of light in determining the positional relationship between rhizoid and protonema are interpreted in terms of a hypothesis proposing light‐induced changes in the structure and mechanical properties of the spore wall.
STRUCTURE OF THE VASCULAR PARENCHYMA IN THE STEM OF LYCOPODIUM LUCIDULUM
Authors: Warmbrodt Robert D. , Evert Ray F.
Published: January 2018

At maturity the vascular cylinder of the stem of Lycopodium lucidulum contains two distinct types of parenchyma cells, one which is always associated with sieve cells, the other with tracheids. The remaining parenchyma cells have characteristics intermediate between the two extremes. The most conspicuous feature of the sieve cell‐associated parenchyma cell is the very dense appearance of its protoplast, due to a high ribosome population and absence of large vacuoles. The large, ramifying nuclei of these cells have numerous connections with the endoplasmic reticulum (ER). The tracheid‐associated parenchyma cells, which are light in appearance, contain many small vacuoles and a relatively small ribosome population. These cells also contain relatively small nuclei and considerable ER cisternae. The parenchymatous elements which have characteristics intermediate between sieve cell‐ and tracheid‐associated parenchyma may or may not be contiguous to the sieve cells or tracheids. An intergradation in wall thickness occurs among parenchyma cells of the vascular cylinder, the thicker‐walled cells being adjacent to the sieve cells, the thinner‐walled ones next to the tracheids. An intergradation also occurs in the frequency of plasmodesmata between the various parenchyma cells. The closer parenchyma cells are to the sieve cells the greater the number of connections between them. No plasmodesmata were found between the tracheid‐associated parenchyma cells.
A COMPARATIVE INVESTIGATION OF PEROXIDASES FROM GERMINATING PEANUTS (ARACHIS HYPOGAEA): ELECTROPHORESIS
Authors: Thomas Dempsey L. , Neucere Nevin J.
Published: January 2018

Dormant seed and organs of 0‐, 1‐, 2‐, 5‐, 8‐, 11‐, and 14‐day‐old plants of Arachis hypogaea L. were homogenized in phosphate buffer and the lipid‐free extracts analyzed for benzidine and pyrogallol peroxidases using starch‐gel electrophoresis. On a wet weight basis, one weak band of benzidine peroxidase activity was detected in dormant cotyledons and three bands in 1‐day cotyledons. In 5‐day tissue, activity had increased significantly; at 14 days, the number of bands had decreased but staining intensity was maintained. In the extract from dormant axis, a single cathodic site of benzidine peroxidase activity was observed; however, on day two there was a marked increase in the number of bands and intensity of reaction in epicotyl and hypocotylradicle tissues. By day 14, the number and density of bands had decreased noticeably in the epicotyl and hypocotyl. Extracts from 14‐day roots exhibited more sites of reaction and greater intensity of staining of benzidine peroxidase than at five days of growth. Localized areas of activity at Rf ‐0.44 and ‐0.52 were present in extracts of all four organs when either benzidine or pyrogallol was used as the hydrogen donor. Although marked similarity existed between banding patterns of organs, qualitative and quantitative ontogenetic differences in peroxidases were apparent.
COMPARATIVE STUDIES OF THE NODAL AND VASCULAR ANATOMY IN THE NEOTROPICAL CYATHEACEAE. I. METAXYA AND LOPHOSORIA
Authors: Lucansky Terry W.
Published: January 2018

Comparative studies of the nodal and vascular anatomy in the monotypic genera Metaxya and Lophosoria are discussed as they relate to the taxonomy and phylogeny of the Cyatheaceae. Both genera are distinctive and primitive with respect to habit, stem and petiole indument, stelar pattern, and nodal anatomy. Metaxya possesses a prostrate, dorsiventral rhizome, whereas a short, upright radial stem occurs in Lophosoria. Trichomes occur on the stems and leaf petioles of these genera. Both Metaxya and Lophosoria have a spiral phyllotaxy, and adventitious buds occur on the petiole bases. The stelar pattern is basically a siphonostele, although frequently a dictyostele is found in Lophosoria. Accessory bundles are lacking in both genera. A characteristic petiole pattern is found in these genera, with an increase in complexity from an undivided strand in Metaxya to the three‐parted petiole pattern in Lophosoria. Data from nodal and vascular anatomy indicate that these taxa are distinct from the other genera in the Cyatheaceae and belong in an independent position at the base of the Cyatheoid line, although in some respects an affinity to members of the Dicksoniaceae is indicated.
POLLEN MORPHOLOGY AND DETAILED STRUCTURE OF FAMILY COMPOSITAE, TRIBE CICHORIEAE. I. SUBTRIBE STEPHANOMERIINAE
Authors: Tomb A. Spencer , Larson Donald A. , Skvarla John J.
Published: January 2018

A survey of pollen morphology in 20 species representing the 11 genera of the North American subtribe Stephanomeriinae by light, scanning electron, and transmission electron microscopy revealed 10 of the 11 genera to have echinate, tricolporate pollen grains, Lygodesmia being the only genus with echinolophate pollen. Sectioned exines of most of the species examined are similar, being composed of ektexine and endexine. The ektexine surface is composed of spines which typically have globose perforate bases. A cavus occurs as a separation between the basis (foot layer) and the columellae in all of the genera examined except Chaetadelpha. Pollen of the two species of Glyptopleura were found to be strikingly different in exomorphology. Pollen of the putatively self‐fertile G. marginata has much shorter spines than the closely related G. setulosa. Atrichoseris, Anisocoma, Calycoseris, Glyptopleura, Pinaropappus, Prenanthella, and most species of Malacothrix have pollen which lack paraporal ridges. The remaining genera, Chaetadelpha, Lygodesmia, Rafinesquia, and Stephanomeria have well‐developed ridges of fused spine bases around the apertures. Pollen characters, particularly those of the aperture region, have been found to be systematically useful in the subtribe, therefore acetolyzed material gives more useful information than untreated pollen.
SPORE ULTRASTRUCTURE OF THE MYXOMYCETE PHYSARUM POLYCEPHALUM
Authors: Randall L. P. , Lynch D. L.
Published: January 2018

Spores of the true slime mold Physarum polycephalum were examined at several stages of their development by means of scanning and transmission electron microscopy. The spores were globose, spine‐covered structures produced within a sporangium enclosed in a tough, noncellular peridium. Cytologically, the spore represented a typical eukaryotic cell, having discrete organelles similar to spores of other myxomycetes. The presence of dictyosomes, helical filaments, and microbodies in these cells, as well as the further elucidation of the cell wall and the “polysaccharide‐containing” areas, represent new contributions to the ultrastructure of the myxomycete spore. Of special interest were observations of metaphase nuclei just prior to spore cleavage, interphase nuclei in young spores, and nuclei in mature spores containing synaptonemal complexes. These observations indicate that in Physarum polycephalum mitosis occurs just prior to spore cleavage, and meiosis takes place after spore cleavage.
MITOSIS IN THE ALGA VACUOLARIA VIRESCENS
Authors: Heywood P. , Godward M. B. E.
Published: January 2018

Details of mitosis in the chloromonadophycean algaVacuolaria virescensCienk. have been studied with the light microscope. The chromosomes are relatively large (up to μ in length at metaphase) and so mitotic stages are readily distinguishable. Chromosomes can be recognized in interphase nuclei as fine strands of chromatin. Contraction of these chromosomes marks the beginning of mitosis and continues progressively until the transition from metaphase to anaphase. Disintegration of nucleoli is complete by late prophase and nucleolar reformation begins in telophase. Some chromosomes exhibit less densely stained regions; centromeres are also present as indicated by their differential staining and by the behavior of chromosomes at metaphase and anaphase. At anaphase progeny chromosomes move apart parallel to the division axis of the nucleus. As anaphase progresses the chromosomes fuse at the polar surface of the progeny chromosome groups. This process continues in telophase and the chromosome groups become more spherical. By the end of telophase nucleolar reformation has begun and the chromosomes have relaxed to their interphase condition.
ABNORMAL GUARD CELL DEVELOPMENT IN AN OLIVE NECROTIC MUTANT OF MAIZE
Authors: Maynard John C. , Mertz Stuart M. , Arntzen Charles J. , Payne Willard W.
Published: January 2018

A study of a mutant variety of Zea mays (ON8147) revealed that the mutant plants, in contrast with normal maize plants, do not exhibit a light‐induced increase in the rate of transpiration, and that the ontogeny of the stomatal complex is abnormal. In later stages of differentiation, the guard cells of mutant plants deteriorate, leaving the mature stomata with only the two subsidiary cells. The subsidiary cells in stomata of mutant leaves are similar to those of normal leaves with respect to their capacity to accumulate K+ in the dark, but they do not lose K+ in the light, as do subsidiary cells of stomata of nonmutant plants. It is suggested that impairment of guard cell function causes death of the mutant plant seedlings primarily by restricting CO2 entry into the leaf.
SYMMETRY AND DEVELOPMENT OF LIMNOBIUM SPONGIA (HYDROCHARITACEAE)
Authors: Wilder George J.
Published: January 2018

Limnobium spongia produces upright vegetative axes and prostrate stolons. The upright axes bear new stolons, whereas the stolons bear new upright axes and fertile and sterile branching systems. Upright axes and fertile and sterile branching systems are all interpreted to have sympodial growth. However, it was not determined whether growth of stolons is monopodial or sympodial. Both stolons and upright axes branch in alternate plastochrons, and branching is achieved solely by the bifurcation of apical meristems. Each meristematic bifurcation is interpreted to represent the formation of a precocious lateral bud. The upright axes develop from presumed precocious lateral buds on stolons, whereas such buds on upright axes produce renewal shoots. Limnobium spongia exhibits a marked degree of mirror‐image symmetry.
SPORE MORPHOLOGY IN THE CYATHEACEAE. I. THE PERINE AND SPORANGIAL CAPACITY: GENERAL CONSIDERATIONS
Authors: Gastony Gerald J.
Published: January 2018

The literature on cyatheaceous spore morphology relative to the presence of a perine layer is reviewed, and evidence based on a sodium‐hydroxide assay is presented indicating that the outer scultpine layer in certain cyatheaceous spores is perine. Perine so defined characterizes Metaxya, paleotropical and certain neotropical species of Sphaeropteris, nearly all species of Alsophila, all species of Nephelea, and certain species of Trichipteris and Cyathea. It is lacking in Lophosoria, many species of Trichipteris and Cyathea, and all species of Cnemidaria. Two major patterns of spore number per sporangium in the family are reported. Lophosoria, Sphaeropteris, Trichipteris, Cyathea, Cnemidaria, and probably Metaxya are characterized by 64‐spored sporangia, whereas most species of Alsophila and all species of Nephelea are characterized by 16‐spored sporangia. The congruence of this generic distribution of sporangial‐capacity types with Tryon's phyletic arrangement of cyatheaceous genera supports the naturalness of his system. The intrasporangial germination of spores retained in dehisced and dispersed sporangia supports the suggestion that decreased spore number per sporangium in Alsophila and Nephelea may relate to the role of the sporangia as dispersal units. The decreased number of spores per sporangium is associated with a trend toward increase in the number of sporangia per sores, with the highest known count approaching 1000 sporangia per sorus. The Alsophila‐Nephelea evolutionary line has probably not been ancestral in the phylogeny of the more advanced groups of ferns.
A COMPARATIVE STUDY OF THE FOLIAR ANATOMY OF LYCOPODIUM SPECIES
Authors: Chu Mel Chih‐Yu
Published: January 2018

A comparative study of the leaves of 31 species of Lycopodium was made. The pattern of tracheids varies with the species. Usually they exhibit annular, helical, reticulate, modified or transition forms; none of the species have advanced phylogenetically beyond the scalariform tracheid stage. Mucilage canals have been found in four species. Tracheids are enclosed by a few to several layers of oblique ended, elongated parenchyma cells in most species, but an endodermis is absent. Vascular bundles are encircled by fiber cells in three species. The mesophyll of most species consists of identically shaped cells, although palisade‐like tissue has been observed in a few species. The epidermal cells vary from elongated to isodiametric and have either undulated or smooth anticlinal walls, which are deeply pitted in some species. The outer epidermal walls are usually thick and heavily cutinized. Stomates are distributed on both surfaces in 18 species, on the abaxial surface in 11 species, and on the adaxial side in only two species. Most stomates are practically isodiametric in surface view, broader than epidermal cells, usually parallel to the vein, and at the same level as the adjacent epidermal cell. A typical guard cell has a prominent outer ledge and a less developed inner ledge of cutin in most species. Six groupings are suggested, based on similarity of leaf structure and the known chromosome numbers.
THE EFFECTS OF GIBBERELLIC ACID AND A GROWTH RETARDANT ON OVULE FORMATION AND GROWTH OF EXCISED PISTILS OF NIGELLA RANUNCULACEAE
Authors: Peterson Curt M.
Published: January 2018

The effects of gibberellic acid (GA3) and the growth retardant AMO‐1618 on ovule formation in excised pistils of Nigella sativa L. were studied by sterile culture techniques. Gibberellic acid promoted pistil growth and inhibited ovule formation. The role of endogenous gibberellins in ovule formation and pistil growth was investigated by adding AMO to the basal medium. Both pistil lengths and ovule formation were reduced significantly with increasing concentrations of AMO. The addition of low concentrations of GA3 to the medium restored pistil growth but did not reverse the inhibitory effect of AMO on ovule formation. The addition of kinetin or indoleacetic acid (IAA) to the medium containing AMO had no effect on pistil lengths. However, with the addition of 10−7 m kinetin, the number of ovules in pistils was increased but not to the levels found in pistils grown in the absence of AMO.
ULTRAVIOLET IRRADIATION AND PIGMENT CELL IDIOBLASTS IN SPIRODELA OLIGORHIZA (LEMNACEAE)
Authors: Witztum Allan
Published: January 2018

InSpirodela oligorhizaandWolffia punctataultraviolet energy induces the conversion of colorless flavans present in scattered idioblasts to red‐brown phlobaphene‐like compounds. The rare appearance of pigment cells in laboratory grown material is discussed.
POLLEN OF BOERLAGIODENDRON: A UNIQUE TYPE IN THE ARALIACEAE
Authors: Tseng Charles C.
Published: January 2018

The pollen ofBoerlagiodendron, one of the most distinct genera of Araliaceae, is unique within the family in its remarkable degree of differentiation of sexine into pertectate and intectate patterns and in its reduced apertures. The unexpanded mesocolpia and the inconspicuous apertures have apparently caused misinterpretation of the pollen morphology ofB. pectinatumin recent literature. A comparative study of several pollen features, together with the meristic characters of carpels and stamens, has demonstrated some significant correlations among them. It appears that the origin of the genus may have been centered around the New Guinea and Solomons areas.
SEPTAL PORE STRUCTURE IN TRICHODERMA SATURNISPORUM
Authors: Hammill Terrence M.
Published: January 2018

Electron microscopic observations of a previously undescribed ascomycetous septal pore structure are presented and discussed. Hyphal septa and septa at the base of phialides in the hyphomycete, Trichoderma saturnisporum Hammill, developed a membrane‐bounded, electron‐opaque septal pore body which was fine‐structurally similar to Woronin bodies. Within a septal pore body, several electron‐transparent layers appeared to develop centripetally from the septal pore rim. The number of layers observed varied from two to about five, with lower numbers being more frequently observed. The electron‐transparent layers perhaps functioned as a vinculum, binding the septal pore body in place. Questions about the origin and function of septal pore bodies are discussed.
CONTROL OF IN VITRO SEPAL DEVELOPMENT OF EXCISED FLORAL BUDS OF AQUILEGIA (RANUNCULACEAE)
Authors: Karpoff Arnold J.
Published: January 2018

Excised floral buds of Aquilegia formosa Fisch. were grown on a coconut‐milk medium containing the minerals and vitamins of Murashige and Skoog, sucrose, and kinetin. The plant growth regulators indoleacetic acid (IAA, 0.5 mg/liter) and gibberellic acid (GA, 2.0 mg/liter) were added singly and in combinations; both were omitted from the control medium. The addition of GA to the basal medium was required to support sepal development on flowers at all phases of development. The formation of stomatal complexes in the epidermis of the sepals occurred only in the presence of GA. Sepals grown in the presence of GA also contained trichoblasts and developing trichomes, while none were formed in the absence of GA. The role of IAA in the development of these idioblasts was not clear but it appeared to have no effect. The hormones GA and IAA had different effects on the growth of the sepals. In the presence of GA the sepals increase in length until comparable with sepals grown in vivo. However, the sepals remained small when GA was omitted from the medium. Upon closer examination of this effect, it was determined that there was a direct proportionality between an increase in cell number in the epidermis and an increase in sepal length. The role of the two hormones in increasing epidermal cell length in sepals was distinct and separate. Exogenous IAA had no effect upon cell division but was required for cell elongation, while GA was required for cell division and had no effect on cell elongation. The GA effect in promoting cell division in the sepals was substantiated by use of autoradiography. If the buds were grown on media with GA, twice as many epidermal cells along the central file incorporated significant amounts of tritiated thymidine. The cell cycle of the epidermal cells of the GA‐treated sepals was ca. 8.7 hr in duration and ca. 13.0 hr if GA was deleted from the medium.