bluuebunny/crossref_metadata_2025 huggingface dataset:
AN ELECTRON‐MICROSCOPIC STUDY OF SPORE WALL STRUCTURE IN THE MUSCI
Authors: McClymont John W. , LARSON Donald A.
Published: January 2018

Spores of 9 species of mosses were embedded in plastic and sectioned for light and electron microscopy. The presence of 4 spore wall layers was found to be of common occurrence. A comparison with pollen wall structure was made. Variations in the layers contributing to the ornamentation were noted. A multi‐layered intine was observed in the genus Archidium. The results indicate that thin sectioning should yield additional sporoderm characteristics of systematic value.
THE HOST‐PARASITE INTERFACE OF ALBUGO CANDIDA ON RAPHANUS SATIVUS
Authors: Berlin Jerry D. , Bowen C. C.
Published: January 2018

The fine structure of the intercellular hyphae of the obligate parasite Albugo candida infecting radish does not differ markedly from that described previously for cells of Peronospora manshurica. The stalked, capitate haustoria do not contain nuclei and are packed with mitochondria and lomasomes. The fungal plasma membrane and cell wall are continuous from the intercellular hypha throughout the haustorium except that there is no evidence of fungal cell wall around a portion of the haustorial stalk proximal to the haustorial head. Within the vacuolate host mesophyll cell, the haustorium is always surrounded by host plasma membrane and with at least a thin layer of host cytoplasm. The host cell wall invaginates at the point of haustorial penetration to form a short sheath around the region of penetration, but normally there is no host cell wall around the balance of the haustorium. About 1% of the haustoria observed were necrotic, and these were invariably walled‐off completely from host cytoplasm by host cell wall. An amorphous, moderately electron‐dense encapsulation lies between the haustorium proper and the host plasma membrane and extends into the penetration region between the sheath and the fungal cell wall. Invaded host cells contain more ribosomal‐rich ground cytoplasm than uninfected cells. Glandular‐like systems of tubules and connecting vesicles are often numerous in host cytoplasm in the vicinity of haustorial heads. These tubules open into the encapsulation, their limiting unit membranes being continuous with the host plasma membrane. We suggest that these represent a secretory mechanism of the host specifically induced by the parasite.
AN ANATOMIC‐SYSTEMATIC STUDY OF THE CLASSICAL TRIBE FESTUCEAE (GRAMINEAE)
Authors: Decker Henry F.
Published: January 2018

Using the classical tribe Festuceae as a frame of reference, 135 grass genera have been examined in an effort to determine natural generic relationships which often have been obscured by parallel and convergent evolution. Studies of embryo and leaf structure, ligules, lodicules, and lemmas have greatly enlarged, verified, and nearly completed existing evidence that the classical concept of the Festuceae is highly artificial and that the tribe contains many genera which are only remotely related. A more nearly phylogenetic system is achieved when more than two‐thirds of these genera are distributed among 4 major groups, which may be worthy of subfamily rank: 55 genera are retained in the festucoid group, 46 are moved to the eragrostoid, 2 to the bambusoid, 13 to the arundoid, and 8 to a recently designated group labelled the centothecoid. Three genera remain unplaced; and material was unavailable or insufficient to make accurate determinations for 8 genera.
VENTURIA INAEQUALIS. XV. HISTOLOGY OF INFECTIONS BY BIOCHEMICAL MUTANTS
Authors: Kline D. M. , Boone D. M. , Keitt G. W.
Published: January 2018

Microscopic examination of apple leaves infected by biochemical mutants of Venturia inaequalis showed that all mutants had penetrated the cuticle and had established themselves in the characteristic subcuticular position without an additional source of their required substances from outside the host. Those mutants that were fully as pathogenic as the wild type developed in vivo comparably to it, but those that were nonpathogenic made very limited growth and, with the exception of 1 requiring choline, failed to develop sufficiently to sporulate. However, the nonpathogenic mutants, with the exception of 1 requiring adenine, grew and sporulated in vivo when their required substances were applied to the surface of the inoculated leaves.
VACUOLAR MASS‐FLOW IN THE FLORAL HAIRS OF STAPELIA
Authors: Benda G. T. A.
Published: January 2018

The flow of vacuolar material was observed in the single‐celled hairs of the corolla of Stapelia grandiflora when the tip region of a hair was cut away and the basal region was supplied with water. The vacuolar flow was a bulk flow independent of the concomitant protoplasmic streaming. The observation has been interpreted in terms of Münich's model for the translation of diffusion into mass‐flow.
CYTOLOGICAL EVIDENCE OF NATURAL INTERTRIBAL HYBRIDIZATION OF TRIPSACUM AND MANISURIS
Authors: Prywer Czeslawa
Published: January 2018

A plant with the morphological aspect of Tripsacum zopilotense, collected at Acahuizotla, State of Guerrero, showed a series of irregularities during meiosis. In diakinesis, 18 bivalents and 9 univalents were observed. In the following stages the univalents stayed separated, like a genome with very different chromosomes. The study of irregularities during meiosis suggests that the plant could be a hybrid which originated from a fusion of an unreduced gamete of T. zopilotense having 36 chromosomes with a reduced gamete of Manisuris cylindrica having 9 chromosomes.
THE DEVELOPMENTAL ANATOMY OF THE ANNONACEAE. I. EMBRYO AND EARLY SEEDLING STRUCTURE
Authors: Hayat M. Arif , Canright James E.
Published: January 2018

Development of the epicotylary meristem is delayed; thus, it apparently has no immediate controlling influence on the procambium initiation either in the hypocotyl‐root axis or in the cotyledons. Contrary to the situation found in most herbaceous dicotyledons, the procambium forms a hollow cylinder in the axis of the mature embryo. The first protophloem differentiates simultaneously in the upper part of the hypocotyl‐root axis, at the base of the cotyledons, and in the cotyledons; protoxylem differentiation follows the same pattern as that of the protophloem. The direct vascular connection between the hypocotyl‐root axis and cotyledons is established early in the mature embryo, and the fundamental aspects of transition phenomena are exhibited by the procambium before mature vascular elements differentiate. In the mature embryos, the pattern of lateral differentiation is irregular in that the number of protoxylem elements present at different levels is quite variable.
THE EFFECTS OF COLCHICINE ON CELLULAR ORGANIZATION IN CHLAMYDOMONAS. I. LIGHT MICROSCOPY AND CYTOCHEMISTRY
Authors: Walne Patricia L.
Published: January 2018

Light‐microscopic investigations and cytochemical analyses were conducted on cells of Chlamydomonas eugametos before, during, and after treatment with colchicine. The effects of the drug on the organization of cellular components were followed at definite intervals and compared with those of control cells in colchicine‐free medium; corresponding studies were made of recovery after treated cells had been returned to a colchicine‐free medium. Upon introduction of 0.005 m colchicine into the culture medium, pronounced changes at the cell surface, in motility, cell size and shape, nuclear volume and shape, and number and arrangement of organelles occurred. When treated cells were returned to a colchicine‐free medium, many underwent a progression of changes and eventually gave rise to apparently normal progeny. Comparative cytochemical studies of untreated and colchicine‐treated cells revealed an increase in amount of starch, protein, and lipid materials to be characteristic of treated cells. The data also suggest that the enlarged walls of treated cells are composed of a complex polysaccharide.
THE KINETICS OF INHIBITION OF AUXIN‐INDUCED GROWTH IN GREEN PEA STEM SEGMENTS BY ACTINOMYCIN D AND OTHER SUBSTANCES
Authors: Penny Pauline , Galston A. W.
Published: January 2018

Inhibitors of nucleic acid and protein synthesis were applied to excised green pea stem sections in the absence and presence of IAA and the effects on growth noted as a function of time. Actinomycin D, which inhibits de novo RNA synthesis, ribonuclease, which degrades RNA, and puromycin, which prevents transfer of aminoacyl residues into the growing polypeptide chain, inhibit section growth only after lengthy lag periods of, respectively, 2, 8 and 5 hr. For actinomycin D and ribonuclease, preincubation in the inhibitor alone, prior to IAA application, does not reduce the lag period, indicating that the lag is not caused by slow penetration of the inhibitor. By contrast, chloramphenicol, which prevents binding of messenger RNA to ribosomes, and p‐fluorophenylalanine, a competitive antagonist of phenylalanine, produce significant inhibitions in the first hour. The implications of these results for the mechanism of auxin action are considered.
A NEW DIAPORTHOPSIS CAUSING BROOMING IN BACCHARIS
Authors: Bonar Lee
Published: January 2018

The symptoms of the disease are listed and illustrated, and the development of the fungus is discussed. The peculiarities of the digestion of the secondary walls of host cells are illustrated and described. A new species, Diaporthopsis sclerophila, is described.
PALEOZOIC SEED STUDIES: ON THE GENUS HEXAPTEROSPERMUM
Authors: Taylor Thomas N.
Published: January 2018

The petrified Paleozoic seed Hexapterospermum is discussed. A new species, H. delevoryii, is described from several seed specimens collected from Middle Pennsylvanian deposits in southern Illinois. The new species is radially symmetrical; approximately 2.5 cm long and 1.3 cm in diam at the widest region. Six primary ribs extend from the integument and give the seed the configuration of a hexagon when sectioned transversely. A thin plate of cells is present at the region of the commissure in each of the ribs. Additional features, not included in the original description of the genus, are described including the occurrence of a pollen‐receiving mechanism consisting of a collar‐like nucellar extension surrounding a central column. Relationships with other Paleozoic seeds are also discussed.
AN ELECTRON MICROSCOPIC STUDY OF THE MATURE MEGAGAMETOPHYTE IN ZEA MAYS
Authors: Diboll Alfred G. , Larson Donald A.
Published: January 2018

With light microscopy maize megagametophytes stained with Alcian blue‐periodic acid‐Schiff (AB‐PAS) reveal acid or neutral polysaccharides in various cell walls. Comparative fine structural studies were made of permanganate‐ or OsO4‐fixed material. Organelle distribution is random in the vacuolate and multinucleate antipodal cells; organelles are abundant; starch is scarce. Antipodal cell walls have large openings forming several syncytia. Some walls are papillate. In the central cell (primary endosperm cell) a thin peripheral layer of cytoplasm surrounds the large vacuole; organelle number is moderate; starch is abundant. The central cell wall is also papillate adjacent to the antipodals and around the egg apparatus. In the synergids organelle distribution is non‐random; nuclei and numerous organelles occupy the micropylar cytoplasm of each synergid; vacuoles dominate the chalazal cytoplasm of these cells. The filiform apparatus stains with AB‐PAS and is composed of both lightly and darkly stained amorphous material. In the egg, organelle distribution is perinuclear with vacuoles proximal to the micropyle; mitochondria are large, abundant and polymorphic; starch is abundant. Nucleolar diameter is five times greater in the central cell and egg than in the antipodal cells and ten times greater than in the synergids. Plasmodesmata occur in all cell walls within the gametophyte, but none appear in the gametophyte wall itself. It is suggested that the antipodals and synergids might be secretory, the latter probably being involved in pollen tube attraction, and that stored metabolites in the central cell and egg cytoplasm support rapid increase in metabolism following fertilization.
THE DISCONTINUITY PLATE, A DEFINITIVE FLORAL CHARACTERISTIC OF THE PSORALEAE (LEGUMINOSAE)
Authors: Lersten Nels R. , Wemple Don K.
Published: January 2018

A survey of the floral vasculature of the Psoraleae and other selected papilionoids was made by using cleared flowers supplemented by microtome sections. The tribe is characterized by xylem discontinuities in the ovary traces in the receptacle. At the base of the ovary the three ovary bundles merge and there is a horizontal proliferation of tracheary elements. This plate‐like xylem expansion is not connected to the xylem of the pedicel and is therefore termed the “discontinuity plate.” Xylem in the petal and stamen traces is commonly discontinuous, but the sepal traces are normal. The discontinuity plate and the associated xylem discontinuities are distinguishing characteristics of the Psoraleae. They have not been found in other legumes.
POLLEN WALL ULTRASTRUCTURE AND ITS BEARING ON THE SYSTEMATIC POSITION OF BLENNOSPERMA AND CROCIDIUM (COMPOSITAE)
Authors: Skvarla John J. , Turner B. L.
Published: January 2018

Electron microscopy is used to help resolve the question of the taxonomic relationships of the genera Blennosperma and Crocidium. Ultrastructural features of their pollen walls indicate that these taxa, long placed in the tribes Helenieae and Senecioneae, respectively, are closely related and that their tribal affinities are with the Senecioneae. Additional ultrastructural observations are made for 40 or more species in the Helenieae and Senecioneae. Three major pollen wall types can be recognized: Anthemoid, Helianthoid and Senecioid. The distribution and significance of these pollen types among the Astereae, Heliantheae, Helenieae, Anthemideae and Senecioneae are discussed.
THE TEMPERATURE OF TREE TRUNKS—CALCULATED AND OBSERVED
Authors: Derby Roger W. , Gates David M.
Published: January 2018

A computer program based on Dusinberre's finite difference method was written to predict the diurnal temperature variations in a tree trunk. The program accounts for solar radiation, thermal radiation, re‐radiation and forced convection. The trunk is heterogeneous and anisotropic. A comparison between observations and predictions is made.
A CORRELATION APPROACH TO CERTAIN PROBLEMS OF POPULATION‐ENVIRONMENT RELATIONS
Authors: Davidson Robert A. , Dunn Rosalie A.
Published: January 2018

A model which visualizes a species as a set of biotype subsets is useful when considering the degree of fitness and homogeneity of populations in their environment. Under founder principle concepts we expect that the number of such subsets tends to decrease as local populations encounter new selective forces in environments and habitats other than those occupied by predecessor populations. Relations between biotypes, considered from the point of view of “variation associated with character correlation” or correlated response and polygene systems, imply that the magnitude of product‐moment correlations between characters can be used as a general measure of selective stress impinging upon populations. Magnitude is defined as the per cent of the total possible pairs of characters whose correlation coefficients are significantly different from zero. The direction of magnitude expected under the founder principle is from low in an undisturbed or ancestral situation to high in an alien one. This hypothesis is demonstrated in the genus Froelichia (AMARANTHACEAE).
INFLUENCE OF TEMPERATURE ON PHYTOTOXICITY OF TRIAZINE HERBICIDES TO PINE SEEDLINGS
Authors: Kozlowski T. T. , Sasaki S. , Torrie J. H.
Published: January 2018

The effects of temperature, over a range of 5 to 30 C, on phytotoxicity of simazine, atrazine, propazine, prometryne, prometone, and ipazine to young Pinus resinosa seedlings were investigated in growth chambers. Herbicides were applied to the soil surface and then mixed into the soil before pine seeds were planted. Development of recently germinated seedlings was then studied for 7 weeks. High temperatures greatly accelerated herbicide toxicity, but the effects of temperature varied greatly among herbicides. Atrazine and simazine were more toxic than other herbicides tested at all temperatures. Toxicity of simazine and atrazine was apparent early, whereas effects of propazine, prometryne, prometone, and ipazine were somewhat delayed. After 7 weeks maximum dry‐weight production of shoots under each herbicide treatment and control occurred at 20 C, with some decreases noted at lower temperatures and marked decreases at progressively higher ones. At 20 C final seedling dry weights following treatment with simazine or atrazine were only one‐third as high as in control plants. Growth was also reduced in lesser amounts by propazine, prometryne, prometone, or ipazine. Variations in phytotoxicity of different triazine herbicides appeared to be related more to their structural differences than their solubilities. Under the constant environmental conditions of the experiments, toxicity symptoms in plants treated with triazine herbicides appeared more rapidly and decisively than in previous field experiments under fluctuating environments. The influence of high temperatures in enhancing triazine toxicity appeared to involve complex interactions of physiological activity of plants and temperature effects on herbicide uptake.
THE KARYOTYPES OF DIPLOID CESPITOSE ZINNIAS: A METHOD AND ANALYSIS
Authors: Torres Andrew M.
Published: January 2018

The karyotypes of the three diploid (n = 10) species of the subg. Diplothrix (Zinnia—Compositae) were compared to determine whether there were any demonstrable differences which could then be sought in their polyploid derivatives. Because many of the chromosomes in a set were too similar to distinguish confidently between them, a method of analysis was developed which measures the similarity of whole sets of chromosomes rather than individual ones. The method consists of measuring the distances between graph‐plotted vertices representing arm lengths of chromosomes of real or paper hybrids and then comparing these distances by means of U tests with those similarly derived for the “parents.” This procedure obviates the need of attempting to identify morphologues (morphologically similar chromosomes) in a somatic diploid root‐tip cell and to equate corresponding pairs of chromosomes from different cells of a single plant or from different species or hybrids. No demonstrable differences in the karyotypes of diploid cespitose zinnias were found. Analysis of previously published data by this method indicated that there has been a general non‐objectivity and non‐operationalism in the determination of homologous chromosomes, and a general but unwarranted assumption that morphologues are in reality genologues (genetically corresponding chromosomes).
CYTOGEOGRAPHY AND CYTOTAXONOMIC RELATIONSHIPS OF RUMEX PAUCIFOLIUS
Authors: Smith Ben W.
Published: January 2018

A cytogeographio survey of western American Rumex paucifolius Nutt. reveals that diploid (2n = 14) and tetraploid (2n = 28) populations occur within the Rocky Mountain var. paucifolius and also within the California var. gracilescens Rech. The meiotic behavior of the chromosomes, the occurrence of aneuploid individuals in the populations, and the occasional occurrence of higher polyploids in nature suggest that the tetraploids are substantially autopolyploid in origin. The two diploid populations are restricted in range and are known, respectively, from high elevations in the southern Sierra Nevada of California and the mountainous region at the headwaters of the Missouri River in Montana and Wyoming. They are patroendemics, for they represent the ancestral diploids from which the more abundant polyploids arose. Both the diploid and the tetraploid populations are dioecious. The available evidence supports the suggestion that sex determination follows an X/Y (Melandrium) scheme in inheritance, but no evidence of heteromorphic sex chromosomes was found. Rumex paucifolius is cytologically and morphologically distinct from any other native North American Rumex. Its characters resemble the R. acetosella group of the subgenus Acetosella, as much as they resemble any known members of subgenus Acetosa. For this and other reasons, the subgenera Acetosa and Acetosella should be combined.
QUANTITATIVE CHANGES IN NUCLEAR DNA ACCOMPANYING POSTGERMINATION EMBRYONIC DEVELOPMENT IN VANDA (ORCHIDACEAE)
Authors: Alvarez Marvin R.
Published: January 2018

Nuclear DNA was measured cytophotometrically in sections and isolated nuclei of the developing embryo of Vanda. The data were interpreted in terms of developmental stage and spatial relationships of the nuclei within the embryo. An equal amount of DNA was found in all meristematic nuclei regardless of the developmental stage of the embryo and was taken as the 2C value. Most of the nuclei in the parenchymatous region fell into the discrete DNA classes, 2C, 4C, and 8C. A significant number, however, had DNA contents above 8C but could not be grouped into classes based on a whole‐number multiple of 2C. Nuclear size was found to vary in direct proportion to DNA content through 8C. Above 8C, correlation between nuclear size and DNA content was poor. The amount of DNA in the nuclei of the parenchymatous region was shown to increase in direct proportion to the distance of the nucleus from the meristem. The average amount of DNA in parenchymal nuclei above 8C was found to increase with the developmental stage of the embryo. Mechanisms which might account for the observed changes in DNA per nucleus are discussed.
EVIDENCE FOR THE PRESENCE OF LIGNIN IN MOSS GAMETOPHYTES
Authors: Siegel S. M.
Published: January 2018

Lignin has been established as a constituent of the gametophyte axes in the giant New Zealand mosses Dawsonia sp. and Dendroligotrichum sp. Isolated products comprised ca. 6‐10% of the dry weight of gametophyte axes and contained 61‐62% C, 6.4‐6.8% H, and 5.1‐7.9% OCH3. Characteristic color reaction and ultraviolet spectra were observed, and alkaline nitrobenzene oxidation yielded perhaps 14‐18% of mixed aldehydes as their 2,4‐dinitrophenylhydrazones. The presence of substantial lignin in these exceptionally tall upright moss gametophytes contrasts strikingly with north temperate species such as Polytrichum, Funaria, Bryum and others, and lends support to the hypothesis that lignification is a mechanically and/or gravitationally regulated process.
COMPARATIVE MEGASPOROGENESIS IN PAPILIONACEAE
Authors: Rembert David H.
Published: January 2018

Megasporogenesis in 16 species of Papilionaceae has been investigated. Archesporial development in Papilionaceae is usually hypodermal, but subhypodermal origin has been observed. The archesporial cell develops directly into the megasporocyte, or divides to produce a parietal cell and a primary sporogenous cell. The parietal cell is always oriented toward the micropylar end of the developing ovule. It may or may not divide to contribute to the nucellar mass as the primary sporogenous cell enlarges to form the megasporocyte. A single megasporocyte is produced in most species investigated. Of those species that form more than one megasporocyte, few develop more than one tetrad of megaspores, and in no case is more than one megagametophyte produced. Meiosis occurs in the megasporocyte to form a tetrad of megaspores. Several variations in tetrad patterns are explored here. Monosporic development is the prevalent condition in Papilionaceae; however, bisporic development does occur.
INITIATION AND EARLY DEVELOPMENT OF THE INFLORESCENCE IN PINEAPPLE (ANANAS COMOSUS, ‘SMOOTH CAYENNE') TREATED WITH ACETYLENE
Authors: Gifford E. M.
Published: January 2018

Pineapple plants ‘Smooth Cayenne’ were made to flower by treatment with acetylene. The organization of the vegetative shoot apex is similar to that of many investigated angiosperms in that it shows a zonate pattern, viz., apical zone, peripheral zone, and central‐core rib meristem. The latter zone is weakly developed. Cytological changes at the shoot apex occur as early as 3 days after treatment; these involve nuclear changes and an increase in ribonucleic acid (RNA) in the cytoplasm of cells of the apical zone. A marked increase in the height of the apex occurs by the 9th day; this is preceded by rib meristem activity in the central core. All component parts of the inflorescence are present and in various stages of development by the 21st day at which time vegetative scales and “crown” leaves are initiated.
A STUDY OF LEAF COMPRESSIONS OF KNIGHTIOPHYLLUM FROM EOCENE DEPOSITS OF SOUTHEASTERN NORTH AMERICA
Authors: Dilcher David L. , Mehrotra Bharati
Published: January 2018

A study was made of the gross morphological characters and cuticular features of several fossil leaves of Knightiophyllum wilcoxianum Berry. These fossil leaves were collected from Eocene deposits exposed in three clay pits in western Tennessee. This investigation refutes the relationship of Knightiophyllum wilcoxianum to the modern genus Knightia and the family Proteaceae as suggested by E. W. Berry.
AQUALINDERELLA FERMENTANS GEN. ET SP. N., A PHYCOMYCETE ADAPTED TO STAGNANT WATERS. II. ISOLATION, CULTURAL CHARACTERISTICS, AND GAS RELATIONS
Authors: Emerson Ralph , Held Abraham A.
Published: January 2018

This newly described member of the Leptomitales was incapable of growth in air on complex media routinely used to culture its nearest relatives. All attempts to isolate it in pure culture were unsuccessful until it was held in an atmosphere established by burning a candle in a sealed jar. Under these conditions it grew vigorously on various complex media and could be readily propagated in the laboratory in pure as well as in unifungal gross cultures. Like a number of other aquatic phycomycetes, A qualinderella fermentans proved to be a strong acid producer, its cultures requiring frequent neutralization during active growth. Work with pure cultures revealed a combination of gas relationships not described before among the fungi. A high level of atmospheric CO2 is required, with good growth occurring between 5 and 20%. Growth also takes place under 99% CO2. Supplemental CO2 is partially replaceable by succinate. A. fermentans exhibits undiminished growth in an atmosphere of CO2‐supplemented hydrogen, essentially devoid of oxygen (leuco‐methylene blue). These features are accompanied by an obligately fermentative energy metabolism. Ecologically, A. fermentans is adapted to an environment poor in oxygen and rich both in carbon dioxide and in fermentable organic matter. Such environments are likely to prevail in the warm, stagnant pools where this water mold has been found growing on submerged fruits. In many aspects of its cultural behavior and metabolism A. fermentans resembles another highly fermentative water mold, Blastocladia (Blastocladiales, Chytridiomycetes). The suggestion is made that in both instances parallel regressive evolution has occurred.
APOLAR EMBRYOS OF FUCUS RESULTING FROM OSMOTIC AND CHEMICAL TREATMENT
Authors: Torrey John G. , Galun Esra
Published: January 2018

Embryos of the brown alga Fucus vesiculosas L. were grown as populations in glass petri dishes in seawater at 15 C in continuous low‐intensity unilateral fluorescent illumination for periods up to 2 weeks. A quantitative estimate of increase in nuclear number was made from acetocarmine squash preparations of samples taken at 12‐or‐24 hr intervals. Over the period of 2‐6 days embryos showed a doubling time of about 12‐18 hr. Under normal seawater culture conditions each embryo formed a single rhizoid. When grown in seawater supplemented with sugar concentrations above 0.4 m, Fucus embryos developed as multicellular spherical embryos lacking rhizoids. In 0.6 m sucrose‐seawater, 97% of the embryos were apolar at 2 days; only 37% were apolar at 4 days, many having recovered from the sucrose inhibition. Some embryos remained apolar after growth in 0.6 m sucrose for 2 weeks. Nuclear counts showed that sucrose‐seawater markedly inhibited the rate of cell division. Other sugars including D‐glucose, D‐fructose, D‐galactose and the sugar alcohol D‐mannitol were also effective. When apolar embryos grown in sucrose‐seawater were returned to seawater, embryo growth resumed at the normal seawater rate, judged from nuclear counts. Such embryos formed multiple rhizoids, varying from two to eight rhizoids per embryo, which developed on the embryo quadrant or half away from the unilateral light. Each of the multiple rhizoids originated from a single small cell in the periphery of the multicellular spherica embryo. Thus the rhizoid‐forming stimulus apparently had been subdivided among a number of the cells of the apolar embryos. The implications of this finding are discussed. Attempts to produce multiple rhizoids by treatment of embryos with indoleacetic acid or 2,4‐dichlorophen‐oxyacetic acid failed. However, embryos treated with 10−4 M or 5 × 10−5 m 2,3,5‐triiodobenzoic acid formed 40 and 30% multiple rhizoids, respectively, suggesting that some chemical, perhaps hormonal, mechanism is involved in polarization and rhizoid initiation in Fucus embryogenesis.
TEMPERATURE AND LIGHT INTENSITY EFFECTS ON GROWTH OF DICTYOSPHAERIUM PULCHELLUM
Authors: Ragsdale Harvey L. , Clebsch Edward E. C.
Published: January 2018

Growth rate and morphological characteristics of Dictyosphaerium pulchcllum were observed from populations maintained at 20 and 25 C under light intensities varying from 100 to 1200 ft‐c. Growth rates, expressed as the number of times the population doubled in chlorophyll content per day, were 0.57 (100 ft‐c) and 1.71 (1200 ft‐c) at 20 C and 0.80 (100 ft‐c) and 2.S7 (1200 ft‐c) at 25 C. Cell size varied between 3.0 and 7.0 μ among all treatments at 20 C and mean cell size increased with an increase in light intensity. Agitation of asexually reproducing populations resulted in up to 95% of a population occurring in a unicellular form. The percentage of uni‐cells was highest in vigorously agitated test tube cultures.
MORPHOLOGICAL STUDIES OF THE NYMPHAEACEAE. V. DOES NELUMBO HAVE VESSELS?
Authors: Kosakai Hatsume , Moseley M. F. , Cheadle V. I.
Published: January 2018

The examination of the primary xylem of roots of Nelumbo has revealed the presence of vessel elements with intra‐face, transversely‐rowed to obliquely‐rowed bordered pitted side walls and scalariformly perforated end walls. Whole mounts of macerated xylem, serial sections of roots, and cells through which a water suspension of India ink particles under slight or no pressure was passed, were the means of investigation. It is our opinion that this discovery does not support theories which derive monocotyledons from the Nymphaeaceae. A discussion leading to this conclusion is presented.
ELECTRON MICROSCOPIC DETERMINATION OF SPECIFIC LEAF SURFACE AREA
Authors: Hsieh J. J. C. , Thomas J. M.
Published: January 2018

A method for the estimation of specific leaf surface area was developed as an aid in the interpretation of radionuclide penetration or gas diffusion data. The estimate was obtained by comparing the contour of the surface with the linear distance of the observed thin cross sections of a leaf replica. The first approximation of the specific surface area of a begonia leaf sample was about 1.6.
OBSERVATIONS ON NORMAL AND ABNORMAL STOMATAL FEATURES IN FOUR SPECIES OF ASPARAGUS L.
Authors: Gopal B. V. , Shah G. L.
Published: January 2018

Structure and development of stomata are reported in four species of Asparagus. The study was made on both foliar and floral organs of two species but only on foliar organs of the other two. The stomata are anomocytic in all organs studied and follow a similar type of development in different organs. Stomata with one subsidiary cell are rare. Abnormalities such as contiguous stomata, degenerate guard cells, and cytoplasmic strands between guard cells of nearby stomata were found. The latter are reported here in monocotyledons for the first time.
DEVELOPMENT OF THE INTERCALARY MERISTEM OF CYPERUS ALTERNIFOLIUS
Authors: Fisher Jack B.
Published: January 2018

The unique vegetative morphology of Cyperus alternifolius with its single elongated internode is ideal for developmental and experimental studies of internodal growth. The elongated internode is established by a primary rib meristem which extends from it to the third or fourth internode of the leaf crown. There is no internal histological differentiation of nodes. A secondary rib meristem, which is initiated later in the subapical region, produces the upper internodes of the leaf crown. Initiation of the secondary rib meristem and the start of extension of the elongated internode are correlated with the appearance of crown buds. The primary rib meristem is confined to a basal intercalary meristem (IM) at an early stage. The IM is mitotically active for many weeks and produces most of the internodal tissues. Quantitative data on percentage of cells dividing and cell length are presented for the IM at various stages of internodal development, Morphogenetic events are correlated with internodal growth. A histological gradient is described in the matured internode. Frequencies of stomates and papillae decrease and ground parenchyma cells shorten markedly toward the base. Epidermal cell length remains relatively constant but decreases in the region of the matured IM. Anatomical data are presented graphically and are correlated with internodal growth.
ORIGIN OF VARIABILITY IN THE SPONTANEA COMPLEX OF SORGHUM BICOLOR
Authors: de Wet J. M. J. , Harlan J. R. , Price E. G.
Published: January 2018

The Spontanea complex of S. bicolor (L.) Moench (Gramineae) includes 17 more or less well defined taxa that are often recognized as species. Four of these, S. elliotii, S. hewisonii, S. niloticum, and S. sudanense, represent stable hybrids between cultivated sorghums and members of Spontanea. The remaining taxa were subdivided among varieties aethiopicum, arundinaceum, verticilliflorum, and virgatum. Cultivated sorghums probably originated from several different races of var. verticilliflorum. Hybridization between cultivated races and members of the wild varieties is increasing the variability of the Spontanea as well as Sativa complexes.
SHOOT AND TREE PRODUCTION FROM ASPEN TISSUE CULTURES
Authors: Winton Lawson L.
Published: January 2018

Trees were produced from firm white callus tissue of triploid quaking aspen (Populus tremuloides Michx.), initiated on a modified Wolter and Skoog defined medium and subcultured monthly for two years. When subcultured to medium without auxin, kinetin or supplements, but containing 0.15 mg/liter BAP (6‐benzylaminopurine), multiple stunted shoots appeared on most inocula. However, at 0.05 mg/liter BAP, only a few vigorous shoots per piece were initiated, but seven rooted on the callus: two in the dark with BAP and five in 200 ft‐c of light with 0.04 mg/liter 2,4‐D. After proliferation of the roots on the medium surface, four shoots elongated and were planted in semi‐sterilized soil, then were given 3100 ft‐c of light for rapid growth into trees. Both light sources were on for 16 hr/day. Two trees were also grown from stunted shoots excised from the callus and rooted in soil.
MITOSIS AND CLAMP FORMATION IN THE FUNGUS PORIA MONTICOLA
Authors: Brushaber J. A. , Jenkins S. F.
Published: January 2018

Nuclear division in P. monticola is in general similar to mitosis in higher organisms. Synchronous division of the nuclei in the dikaryon progresses with clamp development. Mitosis begins with the movement of the centriolar plaques into and under the forming clamp. The pull of the centriolar plaque on the attached nucleolus forms a long strand of nucleolar material. Chromosomes now appear as dense granules at the end of the nucleus proximal to the clamp. At this time the nucleolus moves adjacent to the centriolar plaque and contracted chromosomes. The nuclear membrane at least partially disintegrates, and the nucleolus is released into the cytoplasm where it may persist through telophase. A faintly staining spindle is often observed, and it produces a “double bridge” effect in separating chromatin. Somatic chromosomes are attached together forming strings that appear double and at least partially separated before metaphase.
SORAL AND PINNULE ONTOGENY IN GLEICHENIA LINEARIS
Authors: Bierhorst David W.
Published: January 2018

The margin of the pinnule in G. linearis becomes determined early in ontogeny. The bulk of the lamina is derived from an intercalary meristematic band between the margin and the midvein. The sporangiferous receptacle possesses a pronounced tetrahedral apical cell and has over‐all organization comparable to the apex of an axial entity. The receptacle is traceable to the marginal series just lateral to the apical cell of the pinnule. The receptacle is described as neither marginal nor superficial in origin, but apical, and it is interpreted as a branch of the pinnule.
SECRETORY CELLS OF LILY PISTILS. II. ELECTRON MICROSCOPE CYTOCHEMISTRY OF CANAL CELLS
Authors: Dashek W. V. , Thomas H. R. , Rosen W. G.
Published: January 2018

The secretory cells which line the canal of Lilium longiflorum pistils possess, on the side facing the canal, an elaborate wall which, with associated structures, Rosen and Thomas (1970) termed the “secretion zone.” We examined the secretion zone in the electron microscope following treatment of excised pistil slices with extraction procedures which remove pectin, hemicellulose, cellulose, lipid, or protein. The outer, fibrillar wall (layer 1) of the secretion zone contains protein, pectin, and cellulose. Internal to layer 1 is a granular‐fibrillar wall (layer 2) several microns thick. It consists of outer and inner regions which can be distinguished from each other cytochemically. The granular component is composed of pectin which is not esterified with methyl groups and which may be complexed with protein. The short, randomly dispersed microfibrils of layer 2 were sensitive to procedures which dissolve cellulose. The extraction procedures did not reveal the chemical nature of the “osmiophilic islands” of layer 2. Paramural body membranes appear to be composed of glycoprotein and may function in secretion by serving as sites of pinocytic interchange at the plasmalemma. The origin of stigmatic exudate and the release of canal cell secretion product are discussed.
INFECTION OF AEDES AEGYPTI LARVAE BY AXENIC CULTURES OF THE FUNGAL GENUS SMITTIUM (TRICHOMYCETES)
Authors: Williams Marvin C. , Lichtwardt Robert W.
Published: January 2018

Spores from axenic cultures of Smittium spp., isolated from various geographical locations and from different dipteran hosts (mosquito, black fly, and chironomid larvae), were fed to mosquito larvae (Aedes aegypti). We were able to demonstrate some host specificity at the insect family level, but no significant differences in infectivity by isolates from different geographical areas. Spore germination and thallus attachment were observed in the host hindgut within 1.5 hr post spore ingestion. Preliminary studies indicate that S. culisetae has little effect on A. aegypti larvae when they are reared under conditions that promote pupation within 5–6 days. However, ingestion of large numbers of spores by 1st instar larvae growing under suboptimal nutritional conditions may produce fungal growth detrimental to larvae.
INFLUENCE OF CERTAIN PLANT GROWTH REGULATORS AND CROWN‐GALL RELATED SUBSTANCES ON BUD FORMATION AND GAMETOPHORE DEVELOPMENT OF THE MOSS PYLAISIELLA SELWYNII
Authors: Spiess Luretta D. , Lippincott Barbara B. , Lippincott James A.
Published: January 2018

Bud formation and gametophore development were studied in the moss Pylaisiella selwynii (Kindb.) Steere and Anderson grown from spores in a liquid medium consisting of inorganic salts. Indoleacetic acid and ethrel increased bud formation within a narrow concentration range. Copious bud formation was obtained with the five cytokinins tested at concentrations varying from 5 X 10−6 to 5 X 10−14 M. Except for about 10 % of the buds obtained with 6‐γ, γ‐dimethylallylaminopurine at 5 times 10−14 m, the cytokinin‐induced buds failed to develop into normal gametophores. Octopine, lysopine, and octopinic acid, substances obtained from crown‐gall tumors, increased bud formation at 10−3 m. On lysopine‐treated plants these buds developed into typical gametophores. Gemma‐like structures were obtained with octopine but no gametophores. l‐arginine and l‐lysine, the amino acids which respectively occur in octopine and lysopine, failed to induce gametophore formation although buds were obtained with 10−3 m lysine. γ‐Guanidinobutyric acid induced bud formation at 10−3 m, but these buds developed into highly abnormal gametophores. The failure of buds obtained with many of these treatments to develop into gametophores appeared to result from the formation of new cell walls in other than the normal geometrical relationship during initial divisions of the pro‐bud. The relevance of the findings to the crown‐gall problem is discussed.
SEED PROTEIN PROFILES AND THE ORIGIN OF THE HEXAPLOID WHEATS
Authors: Johnson B. Lennart
Published: January 2018

Protein profiles of Triticum and Aegilops species were obtained by electrophoresis of crude seed extracts on polyacrylamide gels. All subspecies of the hexaploid T. aestivum (AABBDD) showed a very uniform profile that could be closely simulated only by the pattern produced by a protein mixture (2:1) from specific profile types of the ancient tetraploid cultivar T. dicoccum (AABB) and the wild diploid Ae. squarrosa (DD). An exceptional hexaploid pattern occurred only in some accessions of T. aestivum ssp. macha. These results confirm the parentage of the aestivum hexaploids in general as T. dicoccum and Ae. squarrosa and more specifically identify the type of the D‐genome donor. They suggest that these wheats, excepting the aberrant macha types, had essentially a monophyletic origin in southwestern Asia. They favor the hypotheses that the cultivated aestivum wheats were derived from the so‐called primitive spelta complex primarily by mutation of a single gene governing the free threshing character and that alpine spelta represents an element displaced from the area of endemism.
FUNGI OF THE CHESAPEAKE BAY AND ITS TRIBUTARIES. III. THE DISTRIBUTION OF WOOD‐INHABITING ASCOMYCETES AND FUNGI IMPERFECTI OF THE PATUXENT RIVER
Authors: Shearer Carol Ann
Published: January 2018

The effects of changes in salinity and temperature on the distribution of wood‐inhabiting Ascomycetes and Fungi Imperfecti in the Patuxent River were studied. Forty‐one species of Ascomycetes and 83 species of Fungi Imperfecti were collected; Pyrenomycetes and dematiaceous Hyphomycetes predominated. Salinity was the most important factor affecting the distribution of fungi, and the major change in species composition occurred where freshwater and saltwater mix. The ratio of Ascomycetes to Fungi Imperfecti increased with increasing salinity, while the number of species collected generally decreased. Triadelphia heterospora Shearer and Crane was collected only at low temperatures and appears to be the only regularly occurring species whose distribution was affected by temperature. The interaction of temperature and salinity did not affect the distribution of four species that occurred regularly at wide ranges of temperature and salinity. Species composition differed between two limnetic stations, one above and the other below the discharge points of two sewage treatment plants.
THE USE OF A NEW CLEARING TECHNIQUE FOR THE STUDY OF EARLY OVULE DEVELOPMENT, MEGASPOROGENESIS, AND MEGAGAMETOGENESIS IN FIVE SPECIES OF CORNUS L.
Authors: Smith Bruce B.
Published: January 2018

The application of a new clearing technique proved successful for the study of ovule development, megasporogenesis, and megagametogenesis in Cornus asperifolia Michaux., C. stricta Lam., C. amomum Miller, C. florida L., and C. alternifolia L. These were the first studies of embryological features in C. asperifolia and C. stricta. Consistent features for both species include: slightly crassinucellate nucelli, megaspore mother cells, and equal dyads with the upper member obliquely aligned to the parietal cell. Alignment of nucelli of the 4‐nucleate megagametophyte is not the same for both species. More than one mature 8‐nucleate megagametophyte per nucellus was recorded for C. asperifolia. Embryological features not revealed in previous investigations of the other three species include: equal dyad cells for C. alternifolia and C. amomum, although disintegration of defunct megaspores is variable for both species; vacuole formation at the micropylar end at the 2‐nucleate stage of C. amomum; a 4‐nucleate stage in C. amomum and C. alternifolia with different alignments of nuclei; synergids that disintegrate rapidly in both species although antipodal shapes vary for each; and fusion of polar nuclei at varying locations within different species. A prominent hypostase is formed in all five species. Because of embryological features, it is recommended that C. forida be separated from the genus Cornus.
TRANSFORMATION OF ROD‐SHAPED ALGAL CELLS INTO SPHERICAL CELLS
Authors: Sorokin Constantine , Nishino Shirley
Published: January 2018

Transformation of the rod‐shaped algal cells, which before the conversion could be considered as belonging to the genus Stichococcus, into spherical cells was achieved by the action of the tryptic soy broth and some other organic media. Transformation did not involve degradation of the cell wall, and the resulting spheres were not sensitive to osmotic shock. The transformed cells could be propagated as spheres for several months but eventually reverted to the original rod shape. The reversion could be hastened by transferring spherical cells back into inorganic medium and growing the cells autotrophically. For a long time after reversion, the cells maintained characteristics different from those of the original rod‐shaped cells which did not go through the conversion and reversion processes. The reverted cells had a higher rate of heterotrophic growth, a lower rate of autotrophic growth, and a lower capacity for being again transformed into spheres under the influence of tryptic soy broth.
STEM ANATOMY AND INTERNODAL DEVELOPMENT IN PHASEOLUS VULGARIS
Authors: Enright A. M. , Cumbie B. G.
Published: January 2018

Internodal length in Phaseolus vulgaris decreases slightly from one through three, then sharply increases in four, and subsequently decreases toward the apex. Two internodes undergo rapid growth at a given time, although they do not mature concurrently. Early growth of the internode takes place throughout, with later growth limited to successively higher levels. Elongation results from both cell division and cell elongation, and the relative importance of these two phenomena is significant in determining final length. The difference in final length between internodes is brought about by rate rather than period of growth. The procambium is relatively homogeneous in structure, whereas the cambium consists of both fusiform and ray initials. During stem development the vascular meristem gradually acquires the characteristics of the cambium. By the time elongation ceases, the meristem has developed all the characteristics of the cambium.
ELECTRON PROBE MICROANALYSIS OF SILICON DEPOSITION IN THE INFLORESCENCE BRACTS OF THE RICE PLANT (ORYZA SATIVA)
Authors: Soni Sarvjit L. , Parry D. Wynn
Published: January 2018

The deposition of silicon in tissues of the inflorescence bracts of rice has been studied with the electron probe microanalyzer. Tissues for analysis were prepared by means of peels, frozen transverse and longitudinal sections, chromations and macerations. The microanalysis shows the heaviest deposition in a layer external to the abaxial (outer) epidermis. The cells of this epidermis are only sparsely silicified, but the’ imprints of these cells are left on the outer silica layer. In the inner tissues of the bracts, silicon deposition is mostly associated with the cell walls.