bluuebunny/crossref_metadata_2025 huggingface dataset:
PATHOLOGICAL CHANGES IN ULTRASTRUCTURE: EFFECTS OF VICTORIN ON OAT ROOTS
Authors: Hanchey Penelope , Wheeler Harry , Luke H. H.
Published: January 2018

Cells in the interior of susceptible oat roots treated with the disease‐inducing agent victorin exhibit many of the ultrastructural features which characterize the epidermal or outermost root cap cells of untreated roots. An increase in electron density of cell walls fixed in permanganate is the first effect of victorin seen in the root interior. Other early victorin‐induced changes are formation of enlarged, densely stained vesicles by the Golgi apparatus and organization of the endoplasmic reticulum into roughly parallel profiles. All of these features are characteristic of untreated epidermal cells. Victorin also induces the formation of large numbers of lomasome‐like wall lesions and causes a marked increase in the number of nearly spherical, membrane‐bounded structures tentatively identified as spherosomes. Similar lomasome‐ and spherosome‐like structures are much more abundant in the outermost cells of the root cap than in other regions of untreated roots. This suggests that these structures may be characteristic of cells destined to undergo disintegration. Victorin‐induced lesions appear to arise within the cell wall as the result of an activation of wall‐degrading enzymes. An early change which makes the unit structure of the plasma membrane visible over extended areas may account for victorin‐induced changes in permeability. Disrupted plasma membranes and swollen mitochondria are found only in cells heavily damaged by victorin. Many of the effects of victorin resemble those of calcium deficiency and calcium is known to suppress victorin‐induced disease symptoms. This suggests that calcium nutrition may play a role in the pathological changes induced by victorin.
CONTROL OF INTERCALARY GROWTH IN THE SCAPE OF GERBERA BY AUXIN AND GIBBERELLIC ACID
Authors: Sachs R. M.
Published: January 2018

With the inflorescence removed, intercalary growth can be maintained in the scape of Gerbera jamesonii by application of gibberellic acid (GA, gibberellin A3) or indole‐3‐acetic acid (IAA); the latter usually promotes more rapid and greater elongation than the former because of a greater effect on older tissues. Simultaneous application of the two substances, even when both are at optimal levels, promotes more rapid elongation than either substance alone; in fact, the rate of elongation may equal that of the intact scape. In decapitated scapes (receptacle and involucral bracts removed with the inflorescence), GA and IAA promote cell elongation with reduced or no cell division. In deflowered scapes (receptacle and involucral bracts intact) both GA and IAA promote cell division, as well as cell elongation, so that the pattern of scape elongation is nearly the same as that for intact scapes. Apparently the bracts and receptacle contribute something required for cell division which acts in concert with GA and IAA. Deflowered and decapitated scapes elongate at nearly the same rates initially; thus the rate of elongation does not depend on cell division. The ultimate length of the scape is dependent on cell number and, hence, cell division, since deflowered scapes attain greater lengths than those that are decapitated.
OBSERVATIONS ON SCHIZAEA AND ACTINOSTACHYS SPP., INCLUDING A. OLIGOSTACHYS, SP. NOV.
Authors: Bierhobst David W.
Published: January 2018

The filamentous gametophytes of Schizaea fistulosa and S. robusta are similar to those previously described from the section Euschizaea Hook. Gametophytes of Actinostachys intermedia, A. laevigata and A. oligostachys are described with some additional information presented on those of A. melanesica. These are all subterranean and begin as primary, axial bodies which become irregularly tuberous with age as the result of a peripheral thickening meristem. Rhizoids and sex organs are distributed uniformly with antheridia mostly on younger axes and archegonia on older tubers. Vegetative reproduction in Actinostachys gametophytes is by surface budding, rhizoid tip proliferation, or archegonial neck proliferation according to species. Sporangia which appear typically gleicheniaceous are occasionally borne at tips of gametophytic rhizoids of A. oligostachys. Actinostachys and Schizaea archegonia both show pronounced internal jackets with some generic differences. Archegonial initials of Actinostachys are established by oblique divisions similar to those which establish leptosporangial initials. In the embryogeny of Schizaea fistulosa, the first division seems to be oblique establishing the foot mother cell and an outer cell which gives rise to the first leaf, root and stem, the apical cells of which are established when the outer hemisphere is composed of 6–8 cells. Later stages in embryogeny of S. dichotoma suggest those in S. fistulosa, except that in certain embryos the first leaf is of late origin on the stem apex. The embryogeny and embryo structure of Actinostachys are not fernlike in the classical sense, but they invite comparison with the Psilotaceae. The zygote elongates and divides transversely. The inner cell develops into the foot, the outer one into stem apex. The structure of the foot is quite similar to that of the Psilotaceae; it is composed of strands of cells which become intermingled with gametophytic tissue. The first leaf arises on the stem apex and the first root endogenously within the stem after the young sporophyte has broken out of the calyptra. A taxonomic description of A. oligostachys, sp. nov., is presented and it is compared to its presumed closest relative, A. melanesica. Generic demarkations within the Schizaeaceae are discussed. The families Psilotaceae, Stromatopteridaceae and Schizaeaceae (sens. strict, i.e., Schizaea and Actinostachys only) are considered to collectively combine the most primitive features of filicalean ferns.
SIEVE TUBES AND CALLOSE IN ELODEA LEAVES
Authors: Currier H. B. , Shih C. Y.
Published: January 2018

Detachment and incubation of Elodea leaves promoted callose synthesis in all cells, especially in epidermal pits and in sieve tubes. Phloem was detected in the midrib by fluorescent staining of callose induced to form on sieve plates. In EM views of mature sieve elements nucleus and tonoplast were lacking, mictoplasm replaced cytoplasm, mitochondria were fewer in number, and large plastids contained crystalline inclusion bodies. Slime was present as compact aggregates and as individual fibrils in mictoplasm and sieve pores. Deposition of callose is considered in relation to the blockage concept of callose function.
ANGIOSPERM WOOD FROM THE UPPER CRETACEOUS OF CENTRAL CALIFORNIA: PART II
Authors: Page Virginia M.
Published: January 2018

Three species of fossil wood representing two genera are described. The specimens are from a collection of woods from the Upper Cretaceous Panoche formation of central California. Tetracentronites panochetris sp. nov. resembles angiosperm wood in ray structure and vascular pitting but lacks vessels. Plataninium platanoides sp. nov. is similar to the wood of Platanus, and the evidence presented points to a direct relationship. The resemblance between Plataninium cali‐fornicum sp. nov. and the woods of certain Icacinaceae is discussed, but evidence of relationship is inconclusive.
NUMERICAL TAXONOMY OF LIMNANTHACEAE
Authors: Ornduff Robert , Crovello Theodore J.
Published: January 2018

A numerical taxonomic study of the angiosperm family Limnanthaceae is presented. The 21 OTUs include all taxa recognized in a recent monograph of Limnanthes (Mason, 1952), plus Floerkea proserpinacoides, two undescribed Limnanthes species, and two artificial interspecific F1 Limnanthes hybrids. One species (L. montana) was treated as two OTUs: measurements for one OTU were taken from field collections and for the other, from garden‐grown plants. A maximum of 35 characters was used in the numerical analyses. Raw data for each character were given equal weighting by condensation. Coefficients of resemblance were established using the mean character difference (MCD) method. Tryon's clustering technique (called key communality cluster analysis) was used. Three numerical analyses of Limnanthaceae were made: one with all 35 characters (T analysis), one with 18 floral characters (F analysis), and one with 17 pre‐ or post‐anthesis or vegetative characters (V analysis). Relative positions of OTUs in the T and F analyses are substantially different from those in a conventional taxonomic treatment of the family. The V analysis shows many differences from the T and F analyses. In all analyses the two OTUs representing L. montana were closer to other OTUs than to each other. The two hybrid OTUs showed greater resemblance to one parent than to the other and in two analyses one hybrid was not intermediate between the parents. Similarities between the T and F analyses are explained on the basis of the predominance of floral characters in both. The differences between these two analyses on the one hand and the V analysis and phylogenetic arrangement of the family on the other are attributed to parallelisms in the evolution of floral characters associated with iucreasing autogamy in each of the two phyletic lines in the family. Analyses emphasizing floral characters will place evolutionarily remotely related outcrossing OTUs together and unrelated, autogamous OTUs together. Using characters that are mostly unassociated with the breeding system the positions of OTUs in a numerical analysis are similar to their positions in a phylogenetic arrangement. The V analysis agrees best with suggestions concerning phylogenetic affinities among the taxa in the family, and provides a useful context for the generation of further evolutionary hypotheses.
INTERACTION OF TEMPERATURE AND GIBBERELLIN ON POTATO SEED GERMINATION
Authors: Lam Shue‐Lock
Published: January 2018

Recently harvested true seed of potato frequently requires several months for complete germination. Gibberellic acid (GA3) has a pronounced effect on seed germination, but this effect is influenced by temperature. As the temperature approaches 80 F, germination decreases considerably irrespective of GA3 treatment. Potato seed germination is also favored by low temperature, but constant low temperature alone does not insure complete germination of dormant seeds. More than 95% germination of dormant seeds can be obtained within a week either by application of GA3 at low temperature or by diurnal alternation of temperature. A possible mechanism for control of seed germination is discussed.
CHLOROPHYCEAN ALGAE FROM LIMESTONE SPRINGS
Authors: Anderson Daryl J. , Nichols H. Wayne
Published: January 2018

Two new chlorococcalean algae have been isolated from limestone springs and studied in axenic cultures. Their life histories have been elucidated and supplementary physiological attributes reported. The relationships of these species to previously described species of the genus are discussed, and a key to known species of Spongiococcum is presented.
ULTRASTRUCTURAL CHANGES DURING SPORANGIUM FORMATION AND ZOOSPORE DIFFERENTIATION IN BLASTOCLADIELLA EMERSONII
Authors: Lessie Patricia E. , Lovett James S.
Published: January 2018

Samples from synchronized cultures of Blastocladiella emersonii were examined by electron microscopy from the late log phase to the completion of zoospore differentiation. Log‐phase plants contain the usual cytoplasmic organelles but also have an unusual system of large tubules ca. 45 mμ diam that ramify in organized bundles throughout the protoplast. After induction, zoosporangium differentiation requires a 2‐hr period in which the nuclei divide, a cross wall forms to separate the basal rhizoid region, and an apical papilla is produced. Nuclear division in B. emersonii is intranuclear with a typical microtubular spindle apparatus and paired, unequal, extranuclear centrioles at each pole. The papilla is formed by a process of localized cell wall breakdown and deposition of the papilla material by secretory granules. Differentiation of zoospores begins when one of the two centrioles associated with each nucleus elongates to form a basal body. The flagella fibers arise from the basal body and elongate into an expanding vesicle formed by the fusion of small secondary vesicles. The cleavage planes are formed by fusion of vesicles similar to those associated with flagellum initiation. When cleavage is complete, each sporangium contains ca. 250–260 uninucleate spore units with their flagella lying in the cleavage planes. Probable fusion of mitochondria to produce the single mitochondrion of the zoospore occurs after cleavage; the mitochondrion does not take its position around the basal body and rootlets until just before zoospore release. The ribosomal nuclear cap is organized and enclosed by a membrane formed through fusion of many small vesicles during a short period near the end of differentiation.
THE EFFECTS ON CHRONIC GAMMA RADIATION ON THE INTERNAL APICAL CONFIGURATIONS OF THE VEGETATIVE SHOOT APEX OF COLEUS BLUMEI
Authors: Crockett Lawrence J.
Published: January 2018

Clonal plants of a bushy variety ‘Trailing Queen’ of Coleus blumei Benth. were exposed to 600–700 R per day for 28 days. Shoot apices of control and irradiated plants were studied microscopically. The normal vegetative shoot apex has two tunica layers and a corpus which is partly layered and partly composed of randomly divided cells. Five cytohistological zones were observed, including a cup‐shaped zone, imposed upon the tunica‐corpus relationships. Response to gamma radiation resulted in abnormal internal apical configurations. All irradiated shoots was found to have the same internal configurations. Only a single tunica layer broken by occasional periclinal divisions was observed. The cytohistological organization of irradiated apices was different from that seen in the normal shoot tips in that two zones were found. Evidence of a radiosensitivity gradient within the vegetative shoot apex was also observed. The possible significance of the results is discussed.
ANATOMY, HISTOCHEMISTRY AND FINE STRUCTURE OF THE GERMINATING EMBRYO OF PAULOWNIA TOMENTOSA
Authors: Rickson Fred R.
Published: January 2018

The anatomy, morphology and gross histochemistry of the germinating embryo and seedling of Paulownia tomentosa (Scrophulariaceae) is described. Cytohistological changes in the shoot apex are correlated with anatomical and histochemical differences. During the first days of germination and before leaf primordia are formed, there is a gradual increase in staining for cytoplasmic protein and RNA. Once the first leaves are initiated, the staining for these compounds remains constant in the central mother‐cell zone, and further increase in protein and RNA is confined to the developing leaf primordia. Starch grains are found in all areas of the very young apex, but with anatomical maturity the grains are restricted to the central mother‐cell zone. Some electron micrographs point up special cytological features.
THE STOMATA OF NELUMBO NUCIFERA: FORMATION, DISTRIBUTION AND DEGENERATION
Authors: Gupta Shrish C. , Paliwal G. S. , Ahuja Rani
Published: January 2018

Contrary to earlier reports, well‐organized but fewer stomata develop on the lower surface of the leaves of Nelumbo nucifera Willd. during aerial growth. The stomata, however, become obliterated by the readjustment of neighboring epidermal cells. During initial stages of degeneration the guard cells show irregularly thickened walls, disintegrated nuclei, and highly vacuolated cytoplasm. Such abnormal features finally lead to the disappearance of stomata from the lower surface of leaves. The ontogeny, structure and distribution of stomata on leaves, perianth lobes, stamens, receptacles and carpels are described. The stomata are haplocheilic in development and are anomocytic (ranunculaceous) at maturity. The concept of a meristemoid and the significance of this study in taxonomy and phylogeny are discussed.
CHROMOSOMAL AND FLOWERING CHARACTERISTICS IN DWARF MISTLETOES (ARCEUTHOBIUM)
Authors: Wiens Delbert
Published: January 2018

Chromosome numbers and other karyological features of Arceuthobium are reported for all species and subspecific groups in the United States and 7 of the 13 entities occurring in Mexico. The only chromosome number known in the genus is n =14 and the karyotype appears to be fundamentally symmetrical. The bivalents are significantly smaller than in the related genus Phoradendron. No supernumerary chromosomes, sometimes present in Phoradendron, were observed in Arceuthobium. The existence of strong isolating mechanisms, which apparently preclude natural hybridization, is advanced as a possible explanation for the absence of polyploidy in the dwarf mistletoes. The flowering characteristics of the American species are analyzed and classified into three principal groups: (1) winter and early spring flowering species with southern distributions, (2) summer flowering species with more northerly distributions, and (3) spring flowering species with the highest latitudinal distributions, but which essentially complete floral development during the previous summer. A fourth group is intermediate between the first and second categories.
A RECONSTRUCTION OF CELL DEVELOPMENT IN THE SHOOT APEX OF MAIZE
Authors: Steffensen Dale M.
Published: January 2018

Somatic mutations were induced in maize embryos in order to follow the albino‐tissue patterns in mature plants. A reconstruction of cellular development in the shoot apex has been attempted. Two strains of maize were employed, wd/Yg2 and pastel‐8549/y1 for seed irradiation with gamma rays. After mature plants had developed from this radiated seed, the sectored plants were analyzed in detail for their patterns of albino tissue. The location and frequency of these patterns were correlated with cell number at various sites of the initial shoot apex in order to deduce the number of cells contributing to each frequency class. Various lines of evidence lead to the conclusion that the cellular differentiation in the shoot apex is organized and a relatively stable process. Apparently a few cells in the apical dome provided daughter tissue for the upper half of the maize plant. Various sector patterns are diagrammed and the position of their albino tissue is explained in relation to the location of a specific cell in the apex.
STRUCTURE AND DEVELOPMENT OF THE PERIANTH IN DOWNINGIA BACIGALUPII
Authors: Kaplan Donald R.
Published: January 2018

The structure and ontogeny of the calyx and corolla of Downingia bacigalupii Weiler (Campanulaceae; Lobelioideae) were investigated for the purpose of comparing perianth development with previous observations on the floral bract, as well as elucidating the mechanism of development of the zygomorphic, sympetalous corolla. Sepals are uni‐traced with a palmate, reticulate venation. They have basal and apical hydathodes, as well as storage tracheids. Sepals show a reduction in size, venation and hydathode number when compared to the bract. The pentamerous, zygomorphic corolla is bilabiate, consisting of a three‐lobed adaxial lip and a two‐lobed abaxial lip connected by a short tubular region. The constituent petal lobes are also uni‐traced and have a reticulate venation, resembling that of the sepal and bract, but lack storage tracheids and hydathodes. Sepals arise in an adaxial to abaxial succession and are initiated in the outer corpus layer of the floral apex. Expansion of the floral apex follows and is accompanied by the establishment of a second tunica layer. Sepals undergo apical, marginal, and intercalary growth accompanied by acropetal differentiation of procambium. The petals arise simultaneously and are initiated in the second tunica layer and the outer corpus cells. After initiation, the petals exhibit a period of apical and marginal growth followed by intercalary growth. Apical growth in petals is less protracted than in sepals, but plate meristem activity is more extensive. The free petal lobes become temporarily fused by an interlocking of marginal epidermal layers, but they separate at anthesis. Zonal growth beneath the originally free lobes forms the tube and lip regions of the sympetalous corolla. Zygomorphy is evident from the time of initiation of petals and is accentuated by later differential growth. Comparative observations of corolla ontogeny in autogamous species of Doumingia indicate that the reduced corollas in these taxa are derived by a simple process of neoteny.
A COMPARATIVE STUDY OF THE PRIMARY VASCULAR SYSTEM OF CONIFERS. I. GENERA WITH HELICAL PHYLLOTAXIS
Authors: Namboodiri Kadambari K. , Beck Charles B.
Published: January 2018

The primary vascular system of 23 species belonging to 18 genera of conifers with helical phyllotaxis has been investigated with the intent of determining the architecture of the system. Special attention has been given to nodal and subnodal relations of the vascular bundles. The vascular system seems to be composed solely of relatively discrete sympodia, that is, axial vascular bundles from which leaf traces branch unilaterally. Although the discreteness of the sympodia is not immediately apparent because of their undulation and lateral contacts with neighboring ones, close examination, including a statistical analysis of the tangential contacts, seems to reveal that each sympodium maintains its identity throughout. Although two traces may be apparent at nodal levels, the trace supply to a leaf originates, in all species, as a single bundle. An analysis is made of the relationship between the vasculature and the phyllotaxis. It is observed that the direction of trace divergence can be accurately predicted when the direction of the ontogenetic spiral, the angle of divergence of leaf traces, and the number of sympodia are known.
A COMPARATIVE STUDY OF THE PRIMARY VASCULAR SYSTEM OF CONIFERS. III. STELAR EVOLUTION IN GYMNOSPERMS
Authors: Namboodiri Kadambari K. , Beck Charles B.
Published: January 2018

This paper includes a survey of the nature of the primary vascular system in a large number of extinct gymnosperms and progymnosperms. The vascular system of a majority of these plants resembles closely that of living conifers, being characterized, except in the most primitive forms which are protostelic, by a eustele consisting of axial sympodial bundles from which leaf traces diverge. The vascular supply to a leaf originates as a single trace with very few exceptions. It is proposed that the eustele in the gymnosperms has evolved directly from the protostele by gradual medullation and concurrent separation of the peripheral conducting tissue into longitudinal sympodial bundles from which traces diverge radially. A subsequent modification results in divergence of traces in a tangential plane. The closed vascular system of conifers with opposite and whorled phyllotaxis, in which the vascular supply to a leaf originates as two traces which subsequently fuse, is considered to be derived from the open sympodial system characteristic of most gymnosperms. This hypothesis of stelar evolution is at variance with that of Jeffrey which suggests that the eustele of seed plants is derived by the lengthening and overlapping of leaf gaps in a siphonostele followed by further reduction in the resultant vascular bundles. This study suggests strongly that the “leaf gap” of conifers and other extant gymnosperms is not homologous with that of siphonostelic ferns and strengthens the validity of the view that Pterop‐sida is an unnatural group. It supports the position that gymnosperms have evolved from progymnosperms rather than from ferns, and the inclusion of ferns and gymnosperms in separate subdivisions or divisions.
A CORRELATION BETWEEN THE APICAL CELL AND THE HETEROBLASTIC LEAF SERIES IN MARSILEA
Authors: White Richard A.
Published: January 2018

Plants of three species of Marsilea (M. vestita, M. villosa, M. drummondii) were grown in sterile culture under controlled conditions, and stem apices were sampled at one of the three heteroblastic leaf forms typical of this plant: spatulate, bifid, or quadrifid leaves. Statistical analyses were made of the relationship between the area of the apical cell and the leaf form which the plant produces under varied growth conditions. For all three species there is a statistically significant correlation (1% level) between apical cell area and leaf form. The analysis indicates that 83% of the variation in apical cell area in Marsilea vestita, 52% in M. villosa, and 54% in M. drummondii can be related to the change in leaf form. An increase in the glucose concentration of the culture medium increases the average apical cell area, and the addition of the protein synthesis inhibitor 2‐thiouracil at concentrations of 10 mg/liter and 25 mg/liter decreases the average apical cell area. A certain average apical cell area is necessary for the production of a particular leaf form in the series. The area is a relative rather than an absolute size under any one particular growth condition. Any growth condition which inhibits or reverses the increase in apical cell size (which is typical of the normal growth pattern) will inhibit or reverse the normal heteroblastic series. Under constant conditions, the average size at which particular leaf forms develop appears to be species specific. These results confirm a generally held idea that the apex size is related to the heteroblastic leaf series, and they indicate that the area of the apical cell is the key factor rather than the volume or the number of cells of the apex. Undoubtedly the area of the apical cell is only a reflection of the physiological or morphological characteristics of the apical meristem that underlie the heteroblastic leaf series and which currently do not appear to lend themselves to more direct quantitative analysis.
SEASONAL DEVELOPMENT OF THE SECONDARY PHLOEM IN PINUS
Authors: Alfieri Frank J. , Evert Ray F.
Published: January 2018

Functional sieve cells are present at all times in the secondary phloem of Pinus banksiana Lamb., P. resinosa Ait., and P. strobus L. With regard to a given year's growth increment, all but the last‐formed sieve cells (2‐4 layers) cease functioning the same season they are derived from the cambium. The former overwinter and remain functional until new sieve cells differentiate in spring. Toward the end of March undifferentiated cells in the outer margin of the cambial zone begin to differentiate into sieve cells. About a week later, cambial activity (cell division) commences. All early phloem is produced by early May before new xylem differentiation begins. Most sieve cells are differentiated by late August, but a few not until late September. Cessation of function begins in late May or June with formation of definitive callose on sieve areas of the sieve cells which overwintered and continues slowly to sieve cells of the current season's early phloem. By mid‐December all but the last‐formed sieve cells (i.e., those which will overwinter in a functional state) are devoid of contents. Phloem differentiation precedes xylem differentiation by approximately 1 1/2 months. Xylem and phloem production cease more or less simultaneously in August, xylem and phloem differentiation in September.
TEMPORAL AND SPATIAL CHANGES IN PEROXIDASE ACTIVITY DURING FRUIT DEVELOPMENT IN ENCYCLIA TAMPENSIS (ORCHIDACEAE)
Authors: Alvarez Marvin R.
Published: January 2018

Peroxidase activity in the fruit of Encyclia tampensis (Lindl.) Small was investigated at various stages of growth and correlated with the histological changes of megasporogenesis and ovule development. Sites of peroxidase activity in the developing fruit were demonstrated histochemically and soluble proteins were resolved electrophoretically at progressive stages of growth. Peroxidase activity increases linearly with fruit diameter and wet weight and is highest in the portion of the fruit containing the developing ovules. While activity is initially confined to the ovulary walls, the ovules show a marked increase in peroxidase activity which is correlated with the lignification of the integuments in the later phases of development. The peroxidase activity initiated by pollination appears entirely to be that of a single isozymic form.
EFFECTS OF EXOGENOUS AMINO ACIDS ON THE DEVELOPMENT OF MARCHANTIA POLYMORPHA GEMMALINGS
Authors: Dunham Valgene L. , Bryan J. K.
Published: January 2018

The effects of various nitrogenous compounds in concentrations ranging from 10‐4 to 10‐3 m on the growth and morphology of gemmae of Marchantia polymorpha L. were investigated under axenic conditions. Only nine of the 24 compounds tested were effective in altering the normal developmental pattern of this plant. l‐Isoleucine, l‐leucine, l‐methionine or l‐threonine resulted in a disruption of the apical regions at concentrations of 10‐3 m. The addition of lower concentrations of l‐arginine, l‐histidine, l‐hydroxyproline, l‐lysine or l‐tryptophan to the nutrient medium resulted in morphological irregularities. These latter abnormal growth patterns were highly specific for the individual amino acids and ranged from lack of air chamber development to complete thallus disorganization. Both the formation and duration of abnormal developmental patterns were dependent upon the concentration of the amino acids employed. Although the experimental results are inconsistent with certain physiological mechanisms such as a general nitrogen toxicity, alternative possibilities are discussed.
ON THE EFFECTS OF DMSO IN CATION TRANSPORT BY EXCISED BARLEY ROOTS
Authors: Schmid Walter E.
Published: January 2018

Dimethyl sulfoxide (DMSO) in concentrations of up to 10% by volume stimulates the uptake of zinc by excised barley roots. In the same concentration it severely depresses uptake of sodium and of rubidium. It does not seem to affect the permeability of the membrane since roots treated with desorption solutions which were 10% in DMSO did not lose more of the preferred ion than did roots desorbed in solutions not containing DMSO. Oxygen utilization (measured in the Warburg respirometer) was reduced when DMSO was present. It is suggested that DMSO is a poisoning agent which interferes with cation transport by attacking some aspect of metabolism and not by influencing the permeability of the membrane.
ULTRASTRUCTURAL ASPECTS OF CELL ELONGATION, CELLULOSE SYNTHESIS, AND SPORE DIFFERENTIATION IN ACYTOSTELIUM LEPTOSOMUM, A CELLULAR SLIME MOLD
Authors: Hohl Hans R. , Hamamoto Susan T. , Hemmes Don E.
Published: January 2018

Vegetative myxamoebae of Acytostelium leptosomum, a cellular slime mold, have the appearance of typical eucaryotic cells. The presence of dictyosomes has been established. Elongation of the cells during aggregation and culmination appears to be mediated by dense bundles of microfibrils traversing the cells longitudinally. Microtubules are present; however, they are randomly oriented and no correlation can be made with cell elongation or with the direction of the cellulose microfibrils within the stalk. A variety of vesicles, multivesicular bodies, and lysosome‐like vacuoles seems to be involved in producing and transporting stalk material to the vicinity of the stalk. However, only rarely do the vesicles empty their contents directly to the outside of the cells. It seems rather that the fibrillar material of the stalk is assembled near or directly at the plasmalemma, and can then be seen to stream away and become an integral part of the stalk. An unusual structure, the H‐body, is formed in great abundance during culmination indicating its possible involvement in stalk synthesis. The H‐bodies are removed from the cells prior to spore formation together with other portions of the cytoplasm at least partly by a process involving autophagic vacuoles. These vacuoles, which are also present in the spores, appear to be part of a rather complex and extensive vacuolar apparatus including the food vacuoles, contractile vacuoles, lysosome‐like structures, and possibly the H‐bodies. The spore coat consists of a heavy outer wall with a fibrillar substructure and two thin, dense bands lining the inside of the plasmalemma. The fibrillar nature of both the outer spore wall and the stalk was accentuated by using barium permanganate to stain sectioned material.
BASAL STEM ANATOMY OF PSARONIUS
Authors: Stidd Benton M. , Phillips Tom L.
Published: January 2018

The basal stem anatomy of three young sporophytes of Psaronius from the Middle Pennsylvanian of Kansas and Illinois is described. The origin of the second stelar cycle is demonstrated in the transition from a simple, amphiphloic siphonostele to a dicyclic dictyostele. Petioles with C‐shaped vascular strands are attached to the stem in a one‐third phyllotaxy. A root mantle is lacking. Basal stem anatomy of Psaronius is compared with that of living genera of the Marattiaceae.
CHLOROPLAST SPECIALIZATION IN DICOTYLEDONS POSSESSING THE C4‐DICARBOXYLIC ACID PATHWAY OF PHOTOSYNTHETIC CO2 FIXATION
Authors: Laetsch W. M.
Published: January 2018

The C4‐dicarboxylic‐acid pathway of photosynthetic CO2 fixation found in tropical grasses has recently been demonstrated in members of the Amaranthaceae and Chenopodiaceae. In the tropical grasses this CO2‐fixation pathway is correlated with specialized leaf anatomy and chloroplast structure. This investigation was undertaken to determine if leaf cells of some representatives of these other families had structural features similar to those of tropical grasses. The leaf anatomy of Amaranthus edulis and a variety of Atriplex species is very similar and it resembles that of grasses such as sugar cane. Prominent bundle sheaths are surrounded by a layer of palisade cells. Bundle‐sheath cells of Am. edulis have large chloroplasts containing much starch, but the chloroplasts have grana. The palisade cells have much smaller chloroplasts containing very little starch. The bundle‐sheath cell chloroplasts of At. lentiformis have grana, their profiles tend to be ovoid, and they contain abundant starch grains. The palisade cell chloroplasts contain little starch and their profiles are discoid. The bundle‐sheath cells of both species contain mitochondria which are much larger than those in the palisade cells. The chloroplasts in both types of cells in both species have a highly developed peripheral reticulum. This reticulum is composed of anastomosing tubules which are contiguous with the inner plastid membrane. The leaf anatomy and cell ultrastructure of these dicots are similar to those of the tropical grasses possessing this new photosynthetic carbon‐fixation pathway. These morphological features are interpreted as adaptations for the rapid transport of precursors and end products of photosynthesis. A hypothesis is presented stating that the unique morphological and biochemical characters of these plants represent adaptations for efficient and rapid carbon fixation in environments where water stress frequently limits photosynthesis.
EFFECTS OF CARBON DIOXIDE ON THE GROWTH AND MORPHOGENESIS OF MARSILEA
Authors: Bristow J. Michael , Looi Ah‐Sing
Published: January 2018

Increased concentrations of CO2 in air (1–50%) cause young plants of Marsilea vestita to exhibit many characteristics of the water form when they are grown on a solid substrate under sterile conditions. Thus these plants have longer internodes, shorter petioles, more rectangular‐shaped epidermal cells and fewer stomata on the lower leaf epidermis than controls grown in 0.03% CO2. Over a 2‐week period, dry weight increase is considerably greater in 12.5% and 25% CO2 than in 0.03% CO2. Fifty percent CO2 is inhibitory to growth. CO2‐enriched air has the same morphogenetic effect when supplied in the light or the dark. Possible explanations for this effect are discussed.
MOBILIZATION BY PINUS RESINOSA CONES AND SHOOTS OF C14‐PHOTOSYNTHATE FROM NEEDLES OF DIFFERENT AGES
Authors: Dickmann D. I. , Kozlowski T. T.
Published: January 2018

Current‐year, 1‐year‐old, 2‐year‐old, and 3‐year‐old needles of 25‐ to 30‐year‐old Pinus resinosa trees were separately exposed to C14O2 at various times during the growing season. Currently produced C14‐photosynthate was preferentially mobilized in the following order: second‐year cones > current needles > current internodes > first‐year conelets. A changing seasonal pattern was shown in sources of current photosynthate for growth of cones and shoots. One‐year‐old needles were the major source of current photosynthate for growth of both cones and shoot internodes. During June the 2‐ and 3‐year‐old needles contributed appreciable amounts of current photosynthate to both cones and developing shoots, but after late June their contribution was slight. The supply of carbohydrates to all tissues, except 2nd‐year cones, from the three age classes of old needles declined late in the season as tissues mobilized increasingly more carbohydrates from current‐year needles. Nevertheless, the bulk of the C14‐photosynthate produced by current‐year needles was retained by them. The preferential mobilization of carbohydrates by reproductive tissues over vegetative tissues is emphasized as is the importance of both reserve and currently produced carbohydrate for growth of various tissues.
DIFFERENCES IN THE OCCURRENCE AND DISTRIBUTION OF HYDROXYPROLINE‐PROTEINS AMONG THE ALGAE
Authors: Gotelli Inta B. , Cleland Robert
Published: January 2018

Fifty algae from seven phyla have been examined in order to determine whether they contain protein‐bound hydroxyproline and whether this hydroxyproline is concentrated in the cell wall. Green algae, with the exception of Nitella, all contain hydroxyproline, and in most cases it is concentrated in the cell wall. Hydroxyproline is also present in low levels in the brown algae, but here it is concentrated in the soluble proteins. Red algae contain no hydroxyproline. The presence of hydroxyproline in blue‐green algae is variable, but when present the levels are low. It appears, then, that the major algal phyla differ with respect to the distribution and occurrence of hydroxyproline‐proteins.
MEIOSIS IN VITRO: SPOROGENESIS IN CULTURED FERN PLANTS
Authors: DeMaggio A. E.
Published: January 2018

Sporangia containing mature, functional spores can be induced to form on pinnae of Todea barbara sporophytes maintained in nutrient culture. Meiosis is initiated in the sporogenous cells and proceeds to completion in vitro with the formation of viable spores. Sporangial development, meiosis and the production of spores occur in plants which exhibit signs of senescence. Fertile leaves are characterized by a reduction in chlorophyll concentration and total cellular nitrogen when compared to sterile leaves. The data suggest that the process of sporogenesis may be correlated with a reduction in metabolic activity of the leaf.
POLLINATION ADAPTATION IN PEDICULARIS GROENLANDICA
Authors: Macior Lazarus Walter
Published: January 2018

Cinematographic and stereophotographic records indicate that Pedicularis groenlandica is pollinated in the Colorado Front Range by seven species of pollen‐foraging bumblebees (Bombus sp.) to which the nectarless flower is intricately adapted functionally and structurally. Removing pollen by wing vibrations of an oscilloscopically identified frequency significantly distinct from flight vibration frequency, foragers carried pollen loads with up to three foreign pollen types in addition to Pedicularis pollen, which was found in all loads. No direct correlation was evident between flight vibration frequency and combined body‐pollen load weight, ambient air temperature, or forager species. The flower is phenologically and morphologically adapted to the worker caste of apparently any Bombus species available to it throughout the plant's montane‐alpine zone vertical‐distribution range. The evolutionary position of the pollination mechanism is considered in relation to the floral morphology of other species in the genus Pedicularis.
INTERPOPULATIONAL VARIATION IN THE GAMETOPHYTES OF PELLAEA ANDROMEDAEFOLIA
Authors: Pray Thomas R.
Published: January 2018

The development and mature morphology of the gametophytes from both sexual and apogamous populations of the fern Pellaea andromedaefolia were investigated. While most sexual examples were indistinguishable, some differences were noted. An insular collection was distinctive in its variability and irregularity of form. Although the latter was a representative of var. pubescens, other collections of the variety could not be distinguished from var. andromedaefolia on the basis of gametophytic characteristics. The apogamous gametophytes were decidedly more variable in development and often very different from sexual thalli. The mature asexual thalli tended to be more irregular in form and usually sharply divergent from the typical cordate type characteristic of the sexual populations. Each of the five apogamous samples was unique with respect to gametophyte development. The differences among the gametophytes of the various populations do not correlate with the sporophytic characteristics which differentiate the two varieties of the species.
CYTOTAXONOMIC STUDIES IN ELEOCHARIS SUBSER. PALUSTRES: CENTRAL UNITED STATES TAXA
Authors: Harms Larry J.
Published: January 2018

Comparative chromosomal and morphological studies indicate that four species are present in the area surveyed. Eleocharis smallii Britt. is primarily diploid with 2n = 16, although sporadic polyploids with 2n = 36 also occur. E. macrostachya Britt. is morphologically similar with unstable polyploid numbers ranging around 2n = 38 and multivalents and univalents present in meiosis. E. xyridiformis Fern. & Brack., a species generally synonymized with E. macrostachya, is shown to be a morphologically distinct species with 2n = 18, 19, and 20. The 19‐chromosome types are trisomic for one of the long chromosomes, the three homologs pairing in meiosis as a large chain trivalent. The trivalent separates equationally in the first division and preferentially in the second so that only 9‐ or 10‐chromosome pollen grains containing an extra chromosome are formed. Trisomic cytotypes may potentially produce normal (18), reconstituted trisomies (19), or tetrasomic (20) plants, although tetrasomics have not been found. The 20‐chromosome cytotype is not the expected tetrasomic, as it is karyotypically distinct from either the 18 or 19 cytotypes. In all species somatic mutations including translocations, translocation‐retranslocations, and chromosome fragmentation (agmatoploidy) have been observed of which the significance, if any, has not been determined.
PHASE‐MICROSCOPIC OBSERVATIONS OF FUSIONS OF NUCLEI IN SOMATIC CELLS OF A HETEROKARYON OF SCHIZOPHYLLUM COMMUNE
Authors: Parag Yair
Published: January 2018

Pairs of nuclei in apical cells of a common‐B heterokaryon (A41 B41 + A2 B41) of Schizophyllum commune fused prior to the nuclear division. It is assumed that each fusion was followed by a reduction division. Five consecutive fusions and divisions in a single hypha were photographed in situ with a phase microscope. These fusions and reduction divisions are possibly related to the genetically determined phenomenon of somatic recombination as a part of the parasexual cycle in fungi.
FRESHWATER HYPHOMYCETES OF THE NORTHERN APPALACHIAN HIGHLAND INCLUDING NEW ENGLAND, AND THREE COASTAL PLAIN STATES
Authors: Crane J. Leland
Published: January 2018

Twenty‐seven species of freshwater Hyphomycetes from two five‐state areas in the northern Appalachian Highland, New England, and three Coastal Plain states were collected, isolated, and identified. The spores of three fungi which are probably aquatic Moniliales were also studied. Sigmoidea, a new Hyphomycete genus, includes submerged aquatic fungi which produce phialides laterally along the mycelium and sigmoid, multicellular phialospores. Varicosporium giganteum sp. n. produces terminal, hyaline, branched, and multiseptate aleuriospores. The main spore axis has one to four lateral branches which arise successively on one side of this axis. Tricladium marylandicum sp. n. is similar to T. splendens in that the lateral branches are constricted where each branch joins the main spore axis. It differs from this species in that the spore has a blunt apical cell on the main axis and on each of the lateral axes. Three possible methods of dispersal are presented to explain the cosmopolitan distribution of freshwater Hyphomycetes.
NUTRITIONAL COMPARISONS IN THE LEPTOMITALES
Authors: Gleason Frank H.
Published: January 2018

Certain aspects of the nutrition of five genera in Leptomitales, an order of aquatic fungi, were investigated. Asparagine was an adequate nitrogen source for all of the fungi tested. Ammonium sulfate could replace asparagine as the nitrogen source in Mindeniella. No single carbon source would support growth in all of the Leptomitales. Apodachlya and Leptomitus were capable of hydrolyzing proteins and metabolizing amino acids, especially glutamate, proline, leucine, and alanine. Apodachlya, Araiospora, and Sapromyces utilized acetate, succinate, pyruvate and d (–) lactate. Leptomitus, Apodachlya, and Araiospora utilized l(+) lactate and succinate. Only Apodachlya metabolized malate. Three sugars, i.e., glucose, fructose, and sucrose, were excellent carbon sources for Mindeniella and Sapromyces. Both of these fungi were capable of growth and fermentation under anaerobic conditions. Utilization of these sugars was more restricted in Apodachlya, Leptomitus, and Araiospora. Each of the five genera is quite distinct physiologically. The order Leptomitales contains a spectrum of related organisms ranging from strongly fermentative to obligately aerobic. Apodachlya, Leptomitus, and Araiospora are obligately aerobic, while Sapromyces is facultatively fermentative. Mindeniella is strongly fermentative even when grown in media with aeration.
SEPTAL PORES IN THE HETEROBASIDIOMYCETIDAE, PUCCINIA GRAMINIS AND P. RECONDITA
Authors: Ehrlich Mary A. , Ehrlich Howard G. , Schafer John F.
Published: January 2018

The septal pores in uredial mycelium of Puccinia graminis and P. recondita lack the septal swelling and septal pore cap (dolipore‐parenthosome configuration) typically associated with the pores of previously investigated Homobasidiomycetidae and the Tremellales among the Heterobasidiomycetidae. The pores in young hyphae of these two species of Puccinia are characterized by the presence of a cytoplasmic matrix which apparently occludes the pore and acts as a plug, thus preventing the migration of organelles from cell to cell. Large vesicles are typically present at the periphery of the pore matrix and the matrix may be very incompletely bounded by a membrane. Nuclei and other cytoplasmic structures migrate from cell to cell through an opening in the septum lateral to the pore. The available evidence indicates that this peripheral gap in the septum results from a breakdown of a portion of an initially complete septum rather than from incomplete septum formation. In addition to the centripetally formed septa, the hyphae of P. graminis and P. recondita are further compartmentalized by shallow infoldings of the lateral wall and limited unilateral septum formation. There is apparent free passage of cellular material between adjacent compartments.