bluuebunny/crossref_metadata_2025 huggingface dataset:
MORPHOLOGICAL AND EMBRYOLOGICAL STUDIES ON THE LEMNACEAE. I. THE FLORAL STRUCTURE AND GAMETOPHYTES OF LEMNA PAUCICOSTATA
Authors: Maheshwari Satish C. , Kapil R. N.
Published: January 2018

Maheshwari, Satish C., and R. N. Kapil. (U. Delhi, Delhi, India.) Morphological and embryological studies on the Lemnaceae. I. The floral structure and gametophytes of Lemna paucicostata. Amer. Jour. Bot. 50(7): 677–686. Illus. 1963.—In Lemna paucicostata, a locally occurring member of the Lemnaceae, the plant body is represented by a frond which is devoid of lignified elements. The root shows a winged root sheath but does not have root hairs. There are no distinctive layers like the endodermis and xylem. The male archesporium is hypodermal and differentiates normally as in other angiosperms into parietal and sporogenous layers. The tapetum is single‐layered and plasmodial. The partition walls of the anther are not derived by sterilization of the sporogenous cells as believed earlier. The microspore tetrads are isobilateral and decussate, the meiotic divisions being successive. The pollen grains are shed at the 3‐celled stage. The ovary contains a single hemianatropous, bitegminal and crassinucellar ovule. The development of the embryo sac conforms to the Allium type.
PALEOZOIC SEED STUDIES: A NEW PENNSYLVANIAN PACHYTESTA FROM SOUTHERN ILLINOIS
Authors: Taylor Thomas N. , Delevoryas Theodore
Published: January 2018

Pachytesta stewartii, a new species found in Middle Pennsylvanian coal ball deposits in southern Illinois, is 2.5 cm long and approximately 1.5 cm in width at its greatest diameter. Commissured ribs are pronounced near the apex and progressively less distinct toward the base. The integumentary system is delimited into 3 regions: outer sarcotesta, middle sclerotesta, and thin endotesta. Conspicuous in the new species is a pronounced basal extension with an enclosed chamber that may be the result of decomposition of thin‐walled parenchyma cells. Relationships with other species and possible significance of the chalazal chamber are discussed.
NUTRITIONAL STUDIES OF ASCOBOLUS IMMERSUS
Authors: Yu‐Sun Clare C. C.
Published: January 2018

A synthetic medium for vegetative growth and apothecial formation of 2 compatible strains of A immersus has been formulated as follows: KH2PO4, 0.5 g; K2HPO4, 0.6 g; MgSO4·7H2O, 0.5 g; micronutrients, 0.1 ml (Vogel's); asparagine, 5 g (for vegetative growth), or urea, 1 g (for apothecial formation); dextrin (Merck), 20 g; biotin, 5 μg; thiamine, 100 μg; and distilled water, 1 liter. This medium had a pH of 6.2 to 6.7 without adjustment and was satisfactory. For apothecial formation, 20 g Noble agar (Difco) and 2 g cellulose powder (Whatman) were added to the above medium. Apothecial formation was better at 23–24 than at 25–26 C. Light was necessary for apothecial formation. Dextrin, soluble starch, glucose and mannose were satisfactory carbon sources for both vegetative growth and apothecial formation. This fungus could not use lactose, sucrose, sorbose, mannitol, sorbitol or insulin as carbon sources. It could assimilate nitrate in the form of KNO3. Optimum yields were obtained with asparagine, aspartic acid, or glutamic acid as the source of nitrogen. The optimum nitrogen‐carbon ratio for apothecial formation was about 2% dextrin and 0.1% urea. This ratio was given the highest apothecial rating 10. Ascobolus immersus was deficient in the ability to synthesize biotin and thiamine.
OBSERVATIONS ON LEAF AND BUD FORMATION IN HYDROCHARIS MORSUS‐RANAE
Authors: Cutter Elizabeth G.
Published: January 2018

Regular sequences of leaf and bud formation occur in several members of the Hydrocharitaceae, including Hydrocharis, in which buds are normally formed in the axil of every second leaf of the phyllotactic spiral. Leaf inception begins by periclinal divisions of the inner cells of the 2‐layered tunica. Bud formation, which occurs in the apical meristem itself, immediately following the inception of the subtending leaf primordium, begins by divisions in various planes in the corpus, the 2 tunica layers remaining continuous throughout. The young bud meristem soon gives rise to a lateral bud, before leaf formation begins upon it. Because of these and other features, this species is one of considerable morphogenetic interest. Morphogenesis of the whole plant, and in particular the factors controlling the regular sequence of leaf and bud formation, have been and are being investigated experimentally.
COMPARATIVE STUDIES OF NITROGEN FIXATION AND PHOTOSYNTHESIS IN ANABAENA CYLINDRICA
Authors: Cobb Howell D. , Myers Jack
Published: January 2018

Manometric methods were developed to allow short‐time measurements on relatively small amounts of cell material. The methods provided measurement of the nitrogen uptake and oxygen evolution attributable to nitrogen fixation either in the presence or absence of carbon dioxide. The methods were applied to observe effects of cell history, light intensity, temperature, pH, and ammonia on nitrogen fixation and photosynthesis with 2 new and significant findings. Nitrogen fixation is markedly accelerated by a preceding period of cellular nitrogen depletion. Nitrogen fixation is depressed by light intensities greater than those required to saturate photosynthesis.
THE FOURTEEN SPECIES OF ZIZIPHUS INCLUDING SARCOMPHALUS (RHAMNACEAE) INDIGENOUS TO THE WEST INDIES
Authors: Johnston Marshall C.
Published: January 2018

Taxonomic treatment is presented for the 14 species of Ziziphus P. Mill. (Rhamnaceae: Dicotyledoneae) recognized in the West Indies, with key, synonymies, and statements of distribution. New combinations include Z. crenata (Sarcomphalus crenaius Urb.), Z. microdictya (S. microdictyus Urb. & Ekm.), Z. acutifolia (S. acutifolius Griseb.), Z. bidens (S. bidens Urb.), Z. obovata (S. obovatus Urb.), Z. havanensis var. bullata (S. bullatus Urb.), and Z. taylori (S. taylori Britt.). New names include Z. urbani (S. parvifolius Urb. & Ekm.) and Z. grisebachiana (S. divaricatus Griseb.). The available evidence of evolutionary relationships is assessed.
ULTRASTRUCTURE OF THE SECONDARY PHLOEM OF TILIA AMERICANA
Authors: Evert Ray F. , Murmanis Lidija
Published: January 2018

Summer and winter (July and January) samples of secondary phloem of Tilia americana were studied with the electron microscope. Parenchyma cells contain: nuclei, endoplasmic reticulum, ribosomes, plastids, mitochondria and occasional dictyosomes. Well‐defined tonoplasts separate vacuoles from cytoplasmic ground substance. Vacuoles often contain tannins. Lipid droplets are common in cytoplasm. Endoplasmic reticulum–connected plasmodesmata are aggregated in primary pit fields. Companion cells differ from parenchyma cells in having numerous sieve‐element connections, possibly slime, and in lacking plastids. Mature, enucleate sieve elements possess 1–4 extruded nucleoli. Numerous vesicles occupy a mostly parietal position in association with plasmalemma. The mature sieve element lacks endoplasmic reticulum, organelles (except for few mitochondria) and tonoplast. In OsO4– and glutaraldehyde‐fixed elements, slime has a fine, fibrillar appearance. Normally, these fine fibrils are organized into coarser ones which form strands that traverse the cell and the plasmalemma‐lined pores of sieve plates and lateral sieve areas.
A DEVELOPMENTAL STUDY OF GUTTULINOPSIS VULGARIS (ACRASIALES)
Authors: Olive Lindsay S.
Published: January 2018

The cellular slime mold, Guttulinopsis vulgaris E. W. Olive, is a common and widely distributed species. Its myxamoebae have lobose pseudopodia and aggregate, not by streaming, but by movement singly or in small groups into the aggregation center. The resulting shield‐shaped pseudoplasmodium gives rise to one (or possibly more on occasion) whitish, simple or compound sorocarp. Sorocarps are 95–465 μ in height, typically with relatively short, stout stalks and with mucilaginous spore heads that measure 75–350 μ broad. The spores are mostly irregular, with flattened or concave sides, and are surrounded by a thin spore wall. They measure 3.8–9.2 μ diam., or 2.6–7.8 × 3.9–9.2 μ. During sorocarp development the myxamoebae become grouped within membranous compartments both in the sorocarp and pseudoplasmodium. In the upper part of the sorocarp they develop almost entirely into spores, while in the lower stalk region of the sorocarp and in the pseudoplasmodium, some myxamoebae develop into spores while others degenerate. The phylogenetic position of Guttulinopsis is unclear, but the genus is probably not closely related to the Dictyosteliaceae.

This investigation has been supported by National Science Foundation Grants G–44263 and GB‐501. The writer is grateful to Miss Carmen Stoianovitch for her assistance.
THE INTERRELATIONSHIP BETWEEN THE FLOWERING OF DODDER AND THE FLOWERING OF SOME LONG AND SHORT DAY PLANTS
Authors: Fratianne Douglas G.
Published: January 2018

Experiments were conducted to determine the interrelationship between the flowering of Cuscuta campestris Yuncker, a species of the parasitic angiosperm dodder, and the flowering of the short‐day plants Xanthium pennsylvanicum and Glycine max var. Biloxi and the long‐day plants Matricaria parthenoides and Hyoscyamus niger. It was found that dodder flowered only on the host plants which were themselves flowering. The flowering pattern of the host plant appeared to be unaffected by the parasitism of dodder. When nonflowering dodder was introduced to soybean plants which were under noninductive photoperiods, neither dodder nor soybean flowered; but when the soybean plants were then completely defoliated, the dodder on 7 of 9 host plants began to flower. This result indicated the possibility that under noninductive photoperiods the leaves of the host plant produced a substance which inhibited the flowering of the dodder. Other experiments involved the use of soybean plants which had been linked together with bridges of living dodder. One member of each soybean pair was kept on inductive short photoperiods while the other member was kept on noninductive long photoperiods. No transmission of a flowering hormone from the induced member of each pair through the dodder bridges to the noninduced member of the pair could be demonstrated. The results, instead, support the concept that a flowering‐hormone inhibitor is translocated from the noninduced soybean partner to the induced soybean partner via the dodder bridges since the induced partners show a definitely weaker flowering pattern than corresponding photoinduced control plants.
THE OXIDATION OF HYDROGEN SULFIDE BY BEGGIATOA
Authors: Kowallik U. , Pringsheim E. G.
Published: January 2018

Knowledge of the conditions in which Beggiatoa is capable of autotrophic nutrition is incomplete. It is not known whether sulfur‐free trichomes from heterotrophic cultures are able to return to the utilization of H2S‐oxidation. Devices were developed which permitted the supply of pure cultures of Beggiatoa, previously cultivated heterotrophically, with H2S, O2, and CO2. Development in media devoid of organic nutrients was achieved, and subculturing under autotrophic conditions could be repeated indefinitely. The strains used behaved differently with respect to their tendency to grow autotrophically. The ability to dispense with organic substrates corresponds to the place in the groups to which they had previously been assigned. All the strains multiplied better when, under otherwise equal conditions, the inorganic medium was supplemented with acetate, very low concentrations of which were effective. This result may, however, be due to the selection of varieties by the isolation procedure. The mixotrophic tendency of our strains may not be a general feature of the genus. There are indications that the wider forms of Beggiatoa tend more toward autotrophic growth than the narrower ones.
ATTEMPTED HYBRIDIZATION BETWEEN MONOECIOUS AND DIOECIOUS CLONES OF CHARA
Authors: McCracken Michael D. , Proctor Vernon W. , Hotchkiss Arland T.
Published: January 2018

The suggestion has been made that within the genus Chara the condition of monoecism or dioecism is of limited taxonomic significance, and that this character reflects only minor genetic variation, rarely sufficient to prevent hybridization between two otherwise similar clones. Objections have been raised to this suggestion. The present investigation was undertaken to determine whether the eggs of dioecious C. rusbyana could be fertilized by sperm from monoecious C sejuncta, monecious C. zeylanica, or dioecious C. kenoyeri; and in turn whether the eggs of C. sejuncta and C. zeylanica could be fertilized by sperm from C. rusbyana. On the basis of 83 crosses involving 28 clones of the four taxa, we conclude that C. rusbyana is genetically isolated from the other three.
RHIZOCTONIA SOLANI: MITOTIC DIVISION IN VEGETATIVE HYPHAE
Authors: Shatla Mohamed N. , Sinclair J. B.
Published: January 2018

The mode of division in vegetative nuclei of an isolate of Rhizoctonia solani Kühn, (Pellicularia filamentosa [Pat.] Rogers), from diseased cotton seedlings was studied with the aid of light and phase‐contrast microscopy. The studies were made using the squash technique and refluxed aceto‐carmine for staining. Observations showed that mitotic mode of division similar to that in higher plants was present and the haploid chromosome number was four at metaphase. These findings are discussed with respect to the modes of division proposed for vegetative nuclei in the fungi.
INCORPORATION OF H3‐THYMIDINE IN LEAF NUCLEI OF XANTHIUM PENNSYLVANICUM
Authors: Maksymowych R. , Blum M. K.
Published: January 2018

The basic kinetics and the pattern of incorporation of H3‐thymidine was studied in the leaf lamina of Xanthium pennsylvanicum. A method of foliar absorption was used to incorporate the radioisotope into leaf nuclei. The autoradiographic techniques employed provided data on the amount of the isotope incorporated. It was determined that 10 μc/ml (sp. act. 6.7 c/mmole) of H3‐thymidine with 1–8 hr of isotopic growth and 4 hr of postisotopic growth gave the most satisfactory results. The percent of labelled nuclei and the number of grains per nucleus were presented as functions of isotopic and postisotopic growth periods. Distribution of grains in the nuclei approximated the Poisson distribution at 1 hr of isotopic growth. Increased time of isotopic growth changed the pattern of grain distribution. No deleterious effects were observed using an 8‐hr period of isotopic growth, but prolonged incubation time significantly decreased the proportion of mitotic figures in the lamina. The amount of incorporation of the DNA precursor expressed as percent of labelled nuclei was linear to about 16 hr of isotopic growth and thereafter decreased gradually. As indicated by the average number of grains per nucleus, H3‐thymidine incorporation increased to about 16 hr, and soon after reached a saturation level. The percent of labelled nuclei and the number of grains per nucleus decreased as a function of the postisotopic growth period. However, they were significantly greater in the lamina near the vein than in the lamina region at some distance from the vein. The radioactive precursor was initially absorbed by the cells of the lamina and was subsequently translocated into the vascular system. There it was circulated and made available to the dividing cells near veins of the lamina. This region may be a metabolically distinct part of the lamina with significantly higher rates of incorporation and mitotic turnover.
COMPARATIVE MORPHOLOGY OF THE CARPEL IN THE ROSACEAE VII. POMOIDEAE: CHAENOMELES, CYDONIA, DOCYNIA
Authors: Sterling Clarence
Published: January 2018

The multi‐ovulate pomoids, Chaenomeles, Cydonia, and Docynia, all have closed sutures and extensive fusion between carpel and floral cup and between ovular and wing bundles. Although the ovules in Docynia are generally apotropic and few in number (4–7), the ovules in the other two genera are pleurotropic and numerous (15–48). A statistical treatment of the whole tribe of Pomoideae shows that in carpels with open sutures ovular and wing bundles definitely tend to be separate while in those with closed sutures these bundles tend to be fused. To a lesser degree carpels with open sutures also tend to have bitegmic ovules, separate carpels, and a lesser extent of fusion between carpel and floral cup, while carpels with closed sutures tend to have monotegmic ovules, united carpels, and a greater extent of fusion between carpel and floral cup.
OBSERVATION OF THE NUCLEAR BEHAVIOR IN STREPTOMYCES CINNAMONENSIS
Authors: Chen Pearl Liu
Published: January 2018

The nuclear region in the hyphae of Streptomyces cinnamonensis consists of two phases: a dense fibrillar phase and a less dense phase in which the fibrillar phase is embedded. The fibrillar phase occurs in two states of aggregation, a dispersed condition in which a network of fine fibrils is apparent and a more organized condition in which the fibrils appear thicker and more compact and exhibit a variety of configurations. The fibrils may be dispersed throughout the nuclear region, either in a whorled pattern or in a more or less straightened manner aligned along the nuclear axis. They may aggregate toward the center of the nuclear region as a dense mass which may be separated into two daughter groups of fibrils. Often the nuclear region between the two daughter groups of fibrils is subdivided by cytoplasmic invagination. Conversely, the two daughter groups of fibrils divide a second time resulting in four masses of fibrils. Thus several nuclear regions may be located in a common cytoplasmic field. The significance of these findings is discussed.
NUTRITIONAL REQUIREMENTS OF THE CHYTRID KARLINGIA ASTEROCYSTA, AN OBLIGATE CHITINOPHILE
Authors: Murray Carol Lebeda , Lovett James S.
Published: January 2018

The nonfilamentous chytrid, Karlingia asterocysta, has been isolated in pure culture on chitin media and the nutritional requirements of a single‐spore clone investigated. The fungus displayed an absolute requirement for chitin or preformed N‐acetyl‐d‐glucosamine. This requirement could only be relieved partially by glucose in the presence of limiting acetyl glucosamine concentrations. Under similar conditions other carbohydrates were not utilized. Sulfate was used as a sulfur source and either nitrate or ammonium ion served as nitrogen sources, though growth was better with amino acids. The organism had a very low phosphate optimum (5 × 10–5 m) and was inhibited by concentrations at or above 1 × 10–3 m. The optimal pH range extended from 6.0 to 7.5 and growth decreased rapidly at higher or lower pH values. Thiamine was required at a very low concentration; only 2 μg thiamine‐HCl/liter were required for optimal growth. In a rich, agitated medium K. asterocysta completed a single growth cycle (i.e., plant generation) in 70 hr at 25 C.
COMPOSITION OF VOLATILES IN RELATION TO TAXONOMY OF AMERICAN ALLIUMS
Authors: Saghir Abdur Rahman B. , Mann Louis K. , Ownbey Marion , Berg Rolf Y.
Published: January 2018

The North American species of Allium exclusive of A. schoenoprasum and A. tricoccum of Old World affinity are grouped on the basis of morphological similarity into eight discontinuous species alliances typified by A. acuminatum, A. campanulatum, A. canadense, A. cernuum, A. falcifolium, A. kunthii, A. sanbornii, and A. validum, respectively. Representatives of each of these alliances were compared with respect to volatile constituents responsible for characteristic odors by means of gas chromatography. Results indicate that these volatiles provide evidence of relationship useful in the classification of alliums. Uniformity was found in composition of volatiles in the representatives of the A. canadense, A. cernuum, A. kunthii, and A. sanbornii alliances. Variation was observed in the A. acuminatum, A. campanulatum, and A. falcifolium alliances. A. validum was the only species of its alliance studied. Vapors of A. validum contain mostly n‐propyl sulfides (onion‐like odor) as does the cultivated A. cepa. Methyl sulfides (cabbage‐like odor) predominate in the A. sanbornii alliance. A few species of the A. acuminatum and A. falcifolium alliances contain mainly allyl sulfides (garlic‐like odor).
THE MORPHOLOGY OF THE MYRISTICACEAE. I. FLOWERS OF MYRISTICA FRAGRANS AND M. MALABARICA
Authors: Wilson Thomas K. , Maculans Livia M.
Published: January 2018

Floral histology and vascular anatomy of Myristica fragrans Van Houtt. and M. malabarica Lam. have been investigated from serial sections and specimens cleared in chloro‐lacto‐phenol. The flowers are unisexual. The androecium is considered to consist of a whorl of laterally concrescent anthers. The bisporangiate anthers are attached by a ridge of tissue to the terminal part of the androphore. In many cases the number of vascular bundles in the androphore is half the number of anthers. The gynoecium consists of a monocarpellate pistil with basal placentation and a single anatropous ovule. Of the many vascular bundles that enter the base of the carpel, two, because of their position and because they provide vascular traces to the ovule, are designated as ventral bundles. Additional ovular traces are provided by the carpel wall vascular system. These additional traces originate at the top of the locule and descend to the ovule. The similarity between the androecia of these two species and the androecium of the ćnellaceae is noted.
HORMONAL CONTROL OF TRANSLOCATION OF PHOTOSYNTHETICALLY ASSIMILATED 14C IN YOUNG SOYBEAN PLANTS
Authors: Hew C. S. , Nelson C. D. , Krotkov G.
Published: January 2018

The normal supply of growth substances to a young soybean plant was altered by removing the plant's apical meristem and replacing this meristem with an aqueous solution of either indole‐3‐acetic acid (IAA), gibberellic acid (GA), or water. The length of each experiment was 1 hr. In the middle of it, 14CO2 was administered to one of the primary leaves of the plant, and at the end distribution of 14C in various parts of the plant was determined. It was found that an addition of growth substances stimulated translocation in three different ways. Both IAA and GA increased the total amounts of sucrose‐14C translocated, increased the rate of its translocation, and affected the distribution pattern of translocated sucrose throughout the plant. Experiments using IAA‐14C have shown that the action of IAA is on the longitudinal translocation in the stem and not on the transfer of photosynthate from the mesophyll to the conducting tissues of the leaf.
COMPARATIVE MORPHOGENESIS OF THE DIMORPHIC LEAVES OF CYAMOPSIS TETRAGONOLOBA
Authors: Sparks Phillip D. , Postlethwait S. N.
Published: January 2018

Cyamopsis tetragonoloba, guar, produces two leaf forms: a simple leaf and a trifoliate leaf. The steps in the development of each of these forms have been investigated in an attempt to determine the precise point at which the leaf primordium becomes destined to produce one or the other characteristic leaf shapes. Up to 140 μ in length the leaf primordia are morphologically indistinguishable. If a simple leaf is to be formed the marginal meristem remains continuous and initiates only lamina. If a trifoliate leaf is to be formed the continuity of the marginal meristem is interrupted by a group of “pocketal” cells dividing it into an upper lamina meristem and a basal leaflet buttress.
MITOSIS IN THE NON‐ARTICULATED LATICIFER OF EUPHORBIA MARGINATA
Authors: Mahlberg Paul G. , Sabharwal Pritam S.
Published: January 2018

The multinucleate condition in the non‐articulated laticifers of embryos of Euphorbia marginata arises as a result of mitosis. Successive stages of mitosis in the nuclei of the laticifer appear in the form of a wave. No sequence of mitotic stages has been noticed in the neighboring longitudinal tiers of cells. This difference in the mitotic pattern in the laticifer and other parenchymatous cells of the embryo suggests that the synthesis of factor(s) responsible for triggering mitosis occurs within the laticifer and does not diffuse to the surrounding cells. The mitotic waves originate distally from the meristems, either in the cotyledonary or hypocotyl portion of the laticifer, and move uni‐ or bidirectionally along its longitudinal axis. The mitotic stimulus does not start simultaneously in all the laticifers. The variable velocity of the mitotic substance results in aphasic mitotic waves in laticifers of the same embryo. Mitotic aberrations have not been observed in the dividing nuclei of the laticifer. A chromosome estimation made from a polar view of metaphase does not suggest polyploidization in the observed laticifers.
HABITAT DIFFERENCES OF THREE LIATRIS SPECIES AND THEIR HYBRID DERIVATIVES IN AN INTERBREEDING POPULATION
Authors: Hadley Elmer B. , Levin Donald A.
Published: January 2018

The genus Liatris (Compositae) affords a favorable vehicle for an analysis of ecological and spatial isolation and their relationship to hybridization. Three biotically sympatric species, L. aspera, L. cylindracea, and L. spicata, were found within a northeastern Illinois sand prairie. Distribution of the three Liatris species was clearly related to a series of elevation, soil moisture, organic matter, exchangeable cation, and available phosphorus gradients. Liatris aspera occupied the upper slopes and ridge tops which were high in potassium and phosphorus content but low in moisture, organic matter, calcium, and magnesium levels. Liatris spicata occurred on the lower slopes and depressions with high soil moisture, organic matter, calcium, and magnesium levels but low potassium and phosphorus content. The third species, L. cylindracea, was restricted to the intermediate mid slopes. These distributional belts intergraded and created broad zones of overlap with opportunities for hybridization. The extent of hybridization was related to the spatial association of species and the availability of intermediate habitats. Hybrids had relatively narrow habitat preferences, and as such, few of the available spectrum of habitats along the elevational gradients were suitable for their establishment.
THE TIME COURSE OF SIEVE TUBE AND XYLEM CELL REGENERATION AND THEIR ANATOMICAL ORIENTATION IN COLEUS STEMS
Authors: Thompson Neal P.
Published: January 2018

Study of the time course of regeneration around a wound in internode number 5 of Coleus showed that first recognizable developing sieve tubes appear 2 days after wounding. Xylem cells appear 3 days after wounding in intact plants and 2 days after wounding in isolated internodes and internode stumps. Xylem cells regenerate on the same radii with previously existing sieve tubes. Separation of xylem from phloem by a cover slip in the cambial zone at the beginning of the experimental period resulted in formation of radially aligned xylem cells and sieve‐tube strands on the phloem side of the cover slip. The results indicate that IAA moves basipetally in the phloem or cambium. The relationship between causal factors in normal vascular differentiation and in the regenerating vascular system is discussed.
GENETICS OF SELF‐INCOMPATIBILITY IN THE MONOCOT GENERA, ANANAS (PINEAPPLE) AND GASTERIA
Authors: Brewbaker James L. , Gorrez David D.
Published: January 2018

Genetic segregations for self‐incompatibility were obtained and analyzed in Ananas comosus and Gasteria spp. (G. verrucosa X G. picta). A single S locus with multiple alleles and gametophytic control of pollen phenotype was implicated in each genus. Inhibition of pollen‐tube growth in the upper third of the pineapple styles and in the ovaries of Gasteria was confirmed. Allied studies of the genus Hemerocallis revealed stylar inhibition in some species and ovarian inhibition in others. The ovarian site of incompatibility reaction is discussed, and its association with hollow‐styled or styleless species and binucleate pollen is emphasized.
GROWTH AND DEVELOPMENT OF THE MYXOMYCETE PERICHAENA VERMICULARIS. I. CULTIVATION AND VEGETATIVE NUCLEAR DIVISIONS
Authors: Ross Ian K.
Published: January 2018

The isolation and successful two‐membered culture of the homothallic myxomycete Perichaena vermicularis (order Trichiales) is reported for the first time. Comparisons of mitosis in amoebae, zygotes and plasmodia as seen with phase contrast microscopy are made and distinguishing features of the different kinds of nuclear behavior are discussed.
CARPEL NUMBER AS A TAXONOMIC CRITERION IN PANDANUS
Authors: Stone Benjamin C.
Published: January 2018

One of the criteria sometimes used in distinguishing species in the genus Pandanus has been the number of carpels which make up each phalange of the fruit. An investigation of the dependability of this criterion yielded results which do not invalidate its use, but its applicability is restricted. In addition a more precise method of obtaining the information required for the use of the criterion is described, involving counts of carpels‐per‐phalange and phalanges‐per‐cephalium based on whole‐cephalium samples. Graphs illustrate some of the variation with respect to carpel number in certain species of the genus. A specific example of the application of the criterion is provided, as are several other examples without detailed data. Cautious use of and limited dependence on the criterion are suggested, and some cases of variation in carpel number within one species are cited. Like all other taxonomic criteria, it should be used in conjunction with all other data and its applicability evaluated for each particular taxonomic case rather than depended upon for quick solutions to taxonomic problems.
THE INFLUENCE OF HYDROXY‐L‐PROLINE ON ONTOGENY AND MORPHOGENESIS OF THE LIVERWORT, SCAPANIA NEMOROSA
Authors: Basile Dominick V.
Published: January 2018

Previously described procedures which permitted the alteration of the culture medium during the course of development were used to investigate the effects of hydroxy‐l‐proline (hypro) on the gametophytic ontogeny of Scapania nemorosa (L.) Dum. Depending upon the time this compound was supplied during ontogeny, hypro at an initial concentration of 5 × 10–5 m delayed leafy shoot development from protonemata and killed or damaged shoots which had already developed. More significantly, hypro was found to influence morphogenesis profoundly in plants that developed subsequent to treatment. Resulting phenovariations included: modifications in branching pattern, in the size, shape, mode of insertion, and degree of overlapping of lateral leaves; and the unprecedented formation of ventral leaves (underleaves, amphigastria). The finding that low concentrations of exogenous hypro can evoke such modifications is considered to be significant to liverwort taxonomy. The range of phenovariation which occurred in response to hypro, especially the formation of amphigastria, suggests that this compound may be influencing an area, or areas, of metabolism of cardinal importance to speciation and phylogeny in succubous leafy liverworts.
INITIATION AND DEVELOPMENT OF SHOOT‐BUDS FROM PROTONEMATA IN THE MOSS PHYSCOMITRIUM TURBINATUM
Authors: Nebel B. J. , Naylor A. W.
Published: January 2018

Moss protonemata of Physcomitrium turbinatum were grown on mineral nutrient agar in culture tubes under various controlled conditions. By use of the described system individual cells of the protonema were discernible in situ and buds could be detected at the one‐cell stage (initiation) and observed throughout their development. Buds normally arose by differentiation of a lateral filament near the apex of a growing caulonemal (heterotrichous) strand. Other modes of origin were erratic. From various other observations we conclude that the most pertinent morphological assays in studies of bud differentiation are growth of single caulonemal strands and the time they require to initiate a bud. A time course for bud development from the one‐cell stage through the stage of leaf expansion is presented. At 26 C, 2 days elapse between these stages. From the time course, the time of bud initiation could be estimated with a probable accuracy of ±2 hr with only daily observations.
LIGHT, TEMPERATURE AND CARBOHYDRATE REQUIREMENTS FOR SHOOT‐BUD INITIATION FROM PROTONEMATA IN THE MOSS PHYSCOMITRIUM TURBINATUM
Authors: Nebel B. J. , Naylor A. W.
Published: January 2018

Clonal protonemata of the moss Physcomitrium turbinatum were grown on a mineral nutrient, sucrose, agar medium under a wide range of incandescent light intensity, temperature and photo‐period conditions. Shoot‐bud differentiation was assayed as the amount of calendar time and total hours of illumination required between inoculation (protonemal inoculant) and initiation (the one‐celled stage) of the first bud in the colony. There was no correlation between bud initiation and amount of protonemal growth. When temperature was not limiting, bud initiation occurred upon giving a requisite light dose regardless of how the light was divided into photoperiods over various durations of calendar time. We interpret this “cumulative light‐dose” effect to mean that budding was dependent upon a threshold level of some morphogenic substance which was synthesized in strict accordance to light dose and was held in store over dark periods. The relationship between time required for bud initiation and light intensity showed that the rate of synthesis of the substance was linear with the log of light intensity in the range from 30–715 ft‐c. Experiments at low temperature (16 C) indicated that the light reaction was dependent upon substrates provided by dark reactions. Accumulation of the proposed substance was also dependent upon the sparing action of carbohydrate which could be provided either by optimal photosynthesis or exogenous addition of sugar. In the absence of added sugar time required for budding increased in direct relation to increasing proportions of dark periods or decreasing light intensity below the optimal level.
FINE STRUCTURE OF NUCLEAR CRYSTALS IN LEAVES OF TWO DIANTHUS SPECIES
Authors: Weintraub M. , Ragetli H. W. J. , Veto Marga
Published: January 2018

Examination of leaf cells of Dianthus barbatus with the election microscope revealed the presence of crystals in the nuclei, but not in the cytoplasm or in other organelles. They were at first thought to be viral crystalline inclusions, but no evidence could be adduced to support this possibility. The crystals were found in the nuclei of cells from all parts of the leaf, including parenchyma cells of the vascular elements. They were usually 0.5–2 μ long, and occasionally up to 5 μ. In longitudinal section they appeared as electron‐dense striations, about 10–15 mμ wide, alternating with electron‐transparent bands, 6–8 mμ wide. In cross section they had a honeycomb appearance, resulting from closely packed hexagonal elements, with electron‐transparent centers. Similar crystals were found in nuclei of D. chinensis leaf cells, but not in other members of the Caryophyllaceae, including two varieties of D. caryophyllus, D. deltoides, D. arenarius, Silene acaulis, Lychnis chalcedonica, Saponaria calibrica, and Stellaria media. This appears be the first fine structural report of a lattice inclusion in nuclei of cells of healthy higher plants.
INDUCTION OF CELL DIFFERENTIATION IN DISSOCIATED CELLS AND FRAGMENTS OF CALLITHAMNION ROSEUM
Authors: Hawkins Eva Konrad
Published: January 2018

Branching in regenerates of Callithamnion roseum is a phenomenon of cellular differentiation. Starting from single cells or filaments, a gradual morphological change in cell types occurs: from parallel cross‐walled, branchless stalk cells to oblique cross‐walled, branch‐bearing main axis cells. The development of a plating technique and a synthetic sea water medium permits quantitative study of cell differentiation (or branching) in populations of regenerating cells or fragments. The distribution of regenerating fragments on a given plate is non‐random as seen from the fact that it does not conform to the Poisson series. Clustering and attachment of neighboring fragments increases the likelihood of branch initiation. The change with age in the distribution of plated regenerating fragments is presented. Developmental potentialities of 5 fragment types were examined. Each fragment type could give rise to branching regenerates. Although apical fragments composed of more than 10 cells usually branched first in a plate, single, large, basal cells seem to have a greater regenerative capacity than do small apical fragments.
INCLUSIONS OF THE PROPLASTIDS AND VACUOLES IN THE SHOOT APICES OF BRYOPHYLLUM AND KALANCHOË
Authors: Gifford Ernest M. , Stewart Kenneth D.
Published: January 2018

Spherical, membrane‐bound inclusions occur in the proplastids and vacuoles of cells of Bryophyllum and Kalanchoë shoot apices. Evidence is presented indicating that the inclusions arise by the accumulation of material within the cisternae of certain tubular proplastid membranes and are then transferred to vacuoles. The results obtained from electron microscopy and from histochemical studies indicate that the contents of the inclusions are predominantly lipid.
PETRIFIED PLANTS FROM THE UPPER MISSISSIPPIAN OF NORTH AMERICA. II. LEPIDOSTROBUS FAYETTEVILLENSE SP. N.
Authors: Taylor Thomas N. , Eggert Donald A.
Published: January 2018

Structurally preserved arborescent lycopsid fructifications are described from the Fayetteville Shale (Upper Mississippian) of northwestern Arkansas. Specimens of Lepidostrobus fayettevillense sp. n. range from complete cones 22.5 cm long and approximately 1.0 cm in diameter to smaller water‐worn fragments. The cones consist of a central axis bearing closely spaced, spirally arranged sporophylls which extend from the cone axis at right angles. Each sporophyll consists of a pedicel which is turned up at its end to form a distal lamina. Sporangia are large and attached to the adaxial surface of each sporophyll. The vascular cylinder consists of a centrally located exarch protostele at least 1.1 mm in diameter. The new species is compared with morphologically similar lycopsid fructifications of equivalent age.
PHYLOGENETIC IMPLICATIONS OF PHYCOCYANOBILIN AND C‐PHYCOCYANIN
Authors: Chapman D. J. , Cole W. J. , Siegelman H. W.
Published: January 2018

C‐phycocyanin has been prepared from algae representative of various orders and families in the Cyanophyceae and Rhodophyceae. The chromophore phycocyanobilin has been cleaved, purified and crystallized as the dimethyl ester. Each sample was compared with reference phycocyanobilin dimethyl ester and found to be identical on the basis of absorption spectral (ultraviolet, visible and infrared) and chromatographic properties. The phylogenetic implications of these results are discussed.
MORPHOLOGICAL STUDIES OF THE ROOTS OF RED PINE, PINUS RESINOSA. II. FUNGAL COLONIZATION OF ROOTS AND THE DEVELOPMENT OF MYCORRHIZAE
Authors: Wilcox Hugh E.
Published: January 2018

Observations are reported on the distribution and appearance of long‐ and short‐root apices of nursery seedlings and plantation trees. Only emerging lateral roots over 50% of the diameter of the mother roots become long‐roots, and only from 10 to 21% attain this initial size. Short‐roots have rounded apices with small, sharply delimited, hemispherical or lens‐shaped meristematic zones. Long‐roots have pointed apices with paraboloid‐shaped meristematic zones showing light‐absorbing zones near the apex as well as near the base of the paraboloid. In small‐diameter long‐roots, lateral short‐roots tend to be uniformly distributed throughout the increment, but in large‐diameter roots they are closer together at the two ends of the increment. Lateral roots may be missing completely in the largest‐diameter pioneer roots. Both long‐ and short‐roots are inhabited by various species of fungi, mycorrhizal and non‐mycorrhizal. The patterns of fungal distribution in long‐roots vary from the proximal to the distal ends of the seasonal growth increments, depending on root growth and morphology. Mycorrhizal‐forming fungal species appear to predominate during the growing season but non‐mycorrhizal species may become prominent during the dormant season. The reactivation of apical and lateral meristems following dormancy occurs somewhat in advance of growth resumption by the fungi. However, delay in growth of the fungi is usually not long enough to permit emerging laterals to escape infection from the developing Hartig net in the mother root. Very large first‐order laterals of 3–0 seedlings and large pioneer roots in the plantations may ultimately acquire a sufficiently rapid growth rate to escape the fungus. When this occurs lateral roots may be initiated from a fungal‐free zone in the mother root and may become infected later. A very sparse Hartig net suffices for a strong invasion of emerging laterals, because hyphal growth is stimulated in the vicinity of a developing lateral.
CAMBIAL DIVISIONS IN PSEUDOTSUGA MENZIESH
Authors: Sisson Warren E.
Published: January 2018

Mitotic activity in the vascular cambium was determined from nine samples from a single internode in each of four Douglas‐fir (Pseudotsuga menziesii [Mirb.] Franco) trees. Counts of mitotic nuclei and populations of potentially dividing cells in each sample were used to determine the average mitotic index per core. The sampling error was determined for the average mitotic index per core and the internode as a whole. Significant differences were found between the mitotic indexes of samples within the internodes of three of the trees; however, no differences were observed in the rate of division among trees. A significant correlation was established between the number of cells in the cambial zone and the average mitoses per core per sample.
ON THE ULTRASTRUCTURE OF CAMBIUM AND ITS VASCULAR DERIVATIVES. III. THE SECONDARY WALLS OF THE SIEVE ELEMENTS OF PINUS STROBUS
Authors: Srivastava Lalit M.
Published: January 2018

The sieve elements of Pinus strobus have thick, lamellate secondary walls, which are composed predominantly of cellulose and lesser amounts of polyuronides and pectins. Eight to 10 lamellae may be present in walls 2‐3 μ in thickness. Each lamella represents a plane of high cellulose density which results from intersection of two parallel sets of fibrils. Polyuronides and pectins are more or less evenly distributed in the wall, possibly with a greater concentration near the middle lamella and the inner surface. Resemblance of these walls to the so‐called nacré walls is indicated, and it is possible that the two represent the same structure.
TRIBALISM IN THE FAMILY EUPHORBIACEAE
Authors: Hutchinson John
Published: January 2018

A short history of the tribal arrangement in the vast family Euphorbiaceae has been given by Henri Baillon in France, Jean Müller of Argau in Switzerland, George Bentham in England, and Ferdinand Pax in Germany. Speculation follows on the ancestors of the group, considered to be polyphyletic and probably derived from more primitive orders with hypogynous flowers, such as Tiliales and Malvales, Celastrales, and Rhamnales, all of which are fundamentally woody, as are most of the Euphorbiaceae. Considered to be ancient characters are the presence of petals, the lack of a disk, the retention of a vestigial ovary in the male flowers, numerous stamens, and the imbrication of the sepals. The sequence of the tribes is based on these assumptions, culminating in the most advanced, such as Hureae, Dalechampieae, Pereae, Ricineae, Crotoneae, Joannesieae, ending with the most advanced of all, the Euphorbieae. A dichotomous key to the tribes and their descriptions is provided, usually listing only the principal genera with the approximate number of species (in parentheses). A more detailed account will be published in the author's third volume of The Genera of Flowering Plants. Twenty of the tribes are illustrated by drawings by the author of representative genera.
THE OCCURRENCE AND DISTRIBUTION OF ACRASIEAE IN FOREST SOILS. II. EAST AFRICA
Authors: Cavender James C.
Published: January 2018

The tropical forest soils of East Africa do not harbor as many species of cellular slime molds as those of Central America, although the same species dominate populations in both areas. The difference occurs in the incidence of the less frequently isolated Acrasieae, such as the crampon‐based species. As was suggested for European forests, an explanation may lie in the fact that East African forests are not as complex and, therefore, there exists less variety of micro‐habitats for Acrasieae. An alternative but not a mutually exclusive theory is that tropical America represents a center of evolution and distribution for the group. As forest in East Africa becomes more temperate in character because of an increase in altitude, the composition of the acrasian populations changes. In particular, Dietyostelium minutum replaces D. purpureum as a dominant, and the number of species diminishes. A similar change was noted previously in Central America.
MOISTURE AND SALT EFFECTS ON FIRE RETARDANCE IN PLANTS
Authors: Montgomery Kenneth R. , Cheo P. C.
Published: January 2018

The burning characteristics of several fire‐retardant plants and Southern California chaparral shrubs of recognized high flammability were compared in muffle‐furnace tests at 650 C. Fresh terminal growth of Atriplex lentiformis did not burn as readily as comparable material of Salvia mellifera, Quercus dumosa and Rhus laurina. When samples from these species were heat‐dried before testing, no differences in flammability were demonstrated. The relatively high field moisture content of Atriplex appears to be primarily responsible for its reduced flammability. The high ash content of this species had no apparent effect on flammability at 650 C. In burning tests of fresh as well as heat‐dried samples, Cistus ladaniferus and, to a lesser extent, Eriodictyon trichocalyx required longer to burn than the other species tested. These differences were not related to moisture content.
GROWTH REGULATION BY ETHYLENE IN FERN GAMETOPHYTES. I. EFFECTS ON PROTONEMAL AND RHIZOIDAL GROWTH AND INTERACTION WITH AUXIN
Authors: Miller Pauline M. , Sweet Haven C. , Miller John H.
Published: January 2018

Three responses resulted from the treatment with ethylene of dark‐grown gametophytes of Onoclea sensibilis. Elongation of the filament was increased, elongation of the rhizoid was decreased, and cell division was inhibited. The optimal ethylene concentrations were between 0.01 and 0.1 ppm. Filament elongation was very tolerant of high ethylene concentrations, since up to 1,000 ppm did not inhibit growth below control levels. Enclosing cultures of gametophytes in chambers of limited volumes produced all the effects of treatment with ethylene, but the responses to sealing were eliminated if plants were enclosed in a chamber which contained a solution of mercuric Perchlorate. This evidence that gametophytes produced ethylene was substantiated by a direct gas chromatographic demonstration of ethylene formation. The growth‐regulating effects of ethylene and auxin appeared to be independent in filament and rhizoid growth. Inhibition of elongation by supra‐optimal auxin concentrations could not be attributed to an auxin‐stimulated production of ethylene.
VARIABILITY IN THE YEAST HANSENULA HOLSTII
Authors: Herman A. I.
Published: January 2018

In the heterothallic yeast Hansenula holstii morphological variants consisting of a mother cell, stalk, and terminal cell are formed during vegetative growth. Tetrad distribution ratios of clones derived from mother and terminal cells differ. Preceding stalk formation endospore‐like structures form in many cells. A causal relationship may exist between formation of the modified nuclei and change in the segregational patterns in the variants.