bluuebunny/crossref_metadata_2025 huggingface dataset:
SEED COAT MORPHOLOGY IN CORDYLANTHUS (SCROPHULARIACEAE) AND ITS TAXONOMIC SIGNIFICANCE
Authors: Chuang Tsan‐Iang , Heckard Lawrence R.
Published: January 2018

A study of seed coat sculpturing in Cordylanthus (Scrophulariaceae—Rhinantheae) using the scanning electron microscope (SEM) shows that seed surface patterns are characteristic and constant for a given species or a group of species. Seeds of 23 species were examined and classified into four types (irregularly crested, deeply reticulate, shallowly reticulate, and irregularly striate) based on differences in the reticulated seed coat. Anatomical studies of sections with the light microscope show that the reticular patterns result from enlargement of the epidermal cells of the integument, followed by formation of characteristic wall patterns through lignification. Seed characters furnish useful data for formulating the taxonomy of Cordylanthus both on the sectional and subsectional level and for the delimitation of certain species. Seed coat morphology offers evidence for including the genus Dicranostegia in Cordylanthus and for maintaining C. hispidus and C. palmatus as separate species. The distinctness of two seed coat types within section Cordylanthus suggests two major phylogenetic lines within this section.
LATE OVULE AND EARLY EMBRYO DEVELOPMENT IN QUERCUS GAMBELII
Authors: Brown Roy C. , Mogensen H. Lloyd
Published: January 2018

The ovary of Quercus gambelii is tricarpellary and trilocular; each locule contains two anatropous, bitegmic ovules. The formation of a caecum from a chalazal extension of the embryo sac was observed. A central resistant column of cells, which exhibit some continuity with the vascular trace supplying the ovule, remains protruding into the embryo sac from the chalaza until the later stages of embryo development. Early embryogeny is characterized by a nearly vertical first division with both of the derivative cells contributing to the building of the embryo proper. Such observations suggest that the embryogeny of Quercus should be placed in the Piperad or Asterad type rather than the Onagrad type as has been the practice.
FURTHER INVESTIGATIONS ON PHYTOCHROME‐CONTROLLED SUCROSE UPTAKE INTO APICAL BUDS OF ETIOLATED PEAS
Authors: Anand Renu , Galston Arthur W.
Published: January 2018

When etiolated pea epicotyls are severed at the ground level and immersed basally into 14C‐sucrose, Pfr phytochrome promotes both the uptake of label into the terminal bud and the growth of that bud. Movement of label up the epicotyl requires active metabolism; it is inhibited by anaerobiosis, low temperature, and 2,4‐dinitrophenol. Increase in bud label is detectable within 15–30 min and precedes the first detectable increase in growth rate. Stem tissues, whose growth is inhibited by red light, show a corresponding decrease in content of label. Sixty to 70% of the label of the bud is carbohydrate; the remainder is found in organic acids and phosphates, amino acids, and cell wall components. The major metabolic effects of red irradiation are (1) promotion of sucrose hydrolysis, probably through an induction of higher β‐fructofuranosidase activity, and (2) enhanced incorporation of sucrose into ethanolinsoluble wall components.
GENETICS OF SOMATIC CELL FUSION IN TWO ISOLATES OF DIDYMIUM IRIDIS
Authors: Collins O'Neil Ray , Ling Hubert
Published: January 2018

Analysis of progeny from a cross between a Honduran clone and a Panamanian clone of Didymium iridis has revealed existence of five new plasmodial fusion loci in the Panamanian isolate. These are in addition to six which were previously known.
A RESOLUTION OF THE EUGENIA–SYZYGIUM CONTROVERSY (MYRTACEAE)
Authors: Schmid Rudolf
Published: January 2018

Floral anatomy now provides additional, strong evidence confirming the distinctness of the mainly New World Eugenia s. s. and the strictly Old World Syzygium s. l. Most significantly, species of Eugenia s. s. have a transeptal vascular supply to the ovules whereas those of Syzygium s. l. have an axile one. Other features of floral histology and vasculature also support such a division. In addition, a review of the taxonomic literature revealed three hitherto neglected organographic criteria—nature of bracteoles, presence or absence of pubescence, and presence or absence of pseudopedicels—that sharply distinguish between Eugenia s. s. and Syzygium s. l. An ensemble of these and other organographic criteria further demonstrates the basic disparity of these taxa. The organography and histology of flowers of Eugenia s. l. are described in detail, with .26 characters contrasting the Old and New World species included in a table.
CYTOTAXONOMY OF THE ELEOCHARIS TENUIS COMPLEX
Authors: Harms Larry J.
Published: January 2018

Chromosome numbers of 2n = 20, 24, 36, and 38 were found in the various taxa comprising the Eleocharis tenuis complex in the United States. Eleocharis tenuis var. verrucosa, the only taxon in the complex with 2n = 20 is given the new status of a full species [E. verrucosa (Svens.) Harms] and seems most closely allied to two southern members of the subseries Truncatae which are not members of the tenuis complex s. s. Karyotypes and meiotic pairing in artificial hybrids indicate that the remainder of the taxa are derivatives of X = 6 with E. tenuis and one of two cytotypes of E. compressa with the lowest numbers of 2n = 24, although evidence is presented to indicate that they are of amphidiploid origin. A second cytotype of E. compressa with 2n = 36 is a segmental autoallohexaploid, whereas E. elliptica and E. elliptica var. pseudoptera (Svens.) Harms, comb. nov. with 2n = 38 are hyperploid derivatives of 2n = 36.
PINOCYTOSIS IN ROOT CAP CELLS EXPOSED TO URANYL SALTS
Authors: Wheeler Harry , Baker Bonnie Lou , Hanchey Penelope
Published: January 2018

In cap cells of intact plant roots exposed to 1mM uranyl for 30 min or less, uranyl crystals were found only in cell walls and in secretory products which had been extruded from the protoplast. In roots exposed for 10–20 hr to 0.1mm uranyl, packets of uranyl crystals bound to secretory products were found within the protoplasts of those exterior cells which contained accumulations of secretory products between the cell wall and protoplast. Although the evidence indicated that these packets of crystals entered the protoplast pinocytotically, results with these specialized exterior cells did not apply to the vast majority of root cap cells in which, after prolonged exposure to 0.1mm uranyl, crystals were concentrated in vacuoles. In roots exposed to 1 or 5mm uranyl for 1 hr, the plasmalemma of interior cap cells was much thicker (13.1 nm) than normal (8.2 nm), and many invaginations and vesicular structures were found near the protoplast surface. Crystals were confined to cell walls except for a few found in vesicles with thickened membranes. Serial sections indicated that most vesicular structures with thickened membranes were in contact with the cell wall, but a few, including some which contained uranyl crystals, were within the protoplast. These results provide evidence of pinocytotic activity in intact plant cells exposed to a toxic heavy metal.
CHROMOSOME NUMBERS IN COMPOSITAE VIII: HELIANTHEAE
Authors: Solbrig Otto T. , Kyhos Donald W. , Powell Michael , Raven Peter H.
Published: January 2018

One hundred and ninety‐three new counts are reported for the tribe Heliantheae of Compositae, mostly based on determinations of meiotic material, including first counts for the genera Adenothamnus, Chrysogonum, Enceliopsis, Guardiola, Isocarpha, Lipochaeta, Otopappus, and Oyedaea, as well as first counts for 66 species. The original counts are discussed in relation to those previously reported for the tribe, by genera and subtribe. Two‐thirds of the approximately 150 genera and more than a third of the roughly 1500 species have now been examined. The incomplete knowledge of generic relationships in the tribe often make the interpretation of these chromosome numbers difficult. Three observations are documented and discussed: (1) genera with low chromosome numbers are few; (2) genera with aneuploid series are abundant; and (3) the original basic chromosome number in the tribe is probably in the range of x = 8 to x = 12.
APICAL SIZE IN THE DETERMINATION OF COROLLA LOBE NUMBER IN LINANTHUS ANDROSAECUS SSP. ANDROSAECUS
Authors: Stevens Patricia T. , Huether Carl A. , Wilson Thomas K.
Published: January 2018

A hypothesis in the literature suggests that apical size is one of the critical determinants of the number of organs a flower will form. Genetically selected and control lines of Linanthus androsaecus ssp. androsaecus (Polemoniaceae) were used to test this hypothesis. Plants in the selection up (SU) line of this species produce flowers with greater than the normal number of corolla lobes, and plants in the selection down (SD) line produce less than the normal number of corolla lobes. Apices from lateral branches collected from plants just prior to flowering differed in size among these two lines and controls. Plants in the SU line showed an increase in apical diameter in median section while plants in the SD line showed a decrease in apical diameter in comparison to controls. SU plants may be flowering later, and SD plants earlier, than controls. SU and control apices from the main stem, collected from plants in a late stage of vegetative growth, also differed in apical diameter. Increase in the number of apical cells is associated with increased size in SU apices in comparison to controls. Apical size differences associated with petal number appear to become established during vegetative growth by the time the first two pairs of foliage leaves are formed. The selected and control lines of L. androsaecus offer support for the hypothesis that apical size is an important factor in the determination of petal number.
PROMOTION OF PERITHECIAL INITIALS IN MONACROSPORIUM DOEDYCOIDES BY 6–METHYL PURINE
Authors: Galsky Alan G. , Monoson Herbert L. , Pikul Frank J. , Thompson Jeffrey S.
Published: January 2018

The promotion of perithecial initials in the imperfect fungus Monacrosporium doedycoides is enhanced by the addition of the RNA synthesis inhibitor 6‐methyl purine (6‐MP). The addition of two other RNA inhibitors (8‐azaguanine and actinomycin‐D) causes the promotion of initials but not at the magnitude observed with 6‐MP. Application of a protein synthesis inhibitor (cycloheximide), a base analog (5‐fluorouracil), or an amino acid analog (p‐fluorophenyl‐alanine) are not promotive on initial formation and can be inhibitory. The apparent cause for the promotion of perithecial initials in the imperfect fungus is that sexual structures are inhibited by mRNA's synthesized by the organism and the addition of 6‐MP prohibits their synthesis.
ELECTRON MICROSCOPIC OBSERVATIONS OF CULTURED CELLS AND PROTOPLASTS OF AMMI VISNAGA
Authors: Fowke L. C. , Bech‐Hansen C. W. , Gamborg O. L. , Shyluk J. P.
Published: January 2018

Protoplasts were prepared from cultured cells of Ammi visnaga (Umbelliferae) by enzymatic digestion of the cell walls and examined microscopically. Staining of fresh protoplasts with Calcofluor and silver hexamine demonstrated the apparent absence of wall material. Protoplasts contained more cell organelles than the whole cells, particularly endoplasmic reticulum and associated polysomes. The plasmalemma of most protoplasts appeared smooth; some protoplasts were connected by structures resembling plasmodesmata. Multinucleates resulting from fusion were frequently observed.
MONOTROPA UNIFLORA: ULTRASTRUCTURAL DETAILS OF ITS MYCORRHIZAL HABIT
Authors: Lutz Richard W. , Sjolund Richard D.
Published: January 2018

A microscopic survey of the achlorophylus plant Monotropa unijlora L. reveals an ectendotrophic mycorrhizal fungus with dolipore septa associated with the roots. Special transfer regions are found in the root cell wall ensheathing all but the ruptured tip of the fungal intrusion.
EFFECT OF HORMONES AND VITAMIN B12 ON GAMETOPHORE DEVELOPMENT IN THE MOSS PYLAISIELLA SELWYNII
Authors: Spiess Luretta D. , Lippincott Barbara B. , Lippincott James A.
Published: January 2018

Bud formation in the moss Pylaisiella selwynii is greatly enhanced by cytokinins at concentrations as low as 10−12m, yet these buds usually fail to develop into normal gametophores. Various ratios at different concentrations of the cytokinin N‐6‐γ,γ‐dimethylallylaminopurine to indoleacetic acid failed to enhance bud initiation over that obtained with cytokinin alone or to permit normal gametophore development. Deletion of the cobaltous ions from the culture medium prevented the appearance of the few gametophores usually formed in the complete medium, but different amounts of cobaltous ion did not significantly enhance initiation of gametophore development. Bud initiation was enhanced 3‐ to 20‐fold by vitamin B12 at 10−5m or by B12 coenzyme at 10−4m, and the time of appearance of these buds was advanced by 6–12 days compared to control plants. At these concentrations of the B12 compounds the buds formed normal gametophores, but at 10−4m vitamin B12 they grew into callus‐like masses similar to those obtained with cytokinins. Although the effects of B12 on bud initiation and development mimicked those of cytokinins, except in permitting normal development, no additive or synergistic effects were observed when they were tested together. It is suggested that B12 may play a regulatory role in the control of gametophore initiation and development in mosses.
THE POLLINATION ECOLOGY OF PEDICULARIS ON MOUNT RAINIER
Authors: Macior Lazarus Walter
Published: January 2018

Six native species of Pedicularis in Mount Rainier National Park in Washington State were studied for their reproductive relationships with animal pollinators. Cinematographic and stereophotographic records revealed pollination of the nectariferous P. bracteosa and P. rainierensis by upright, nectar‐foraging queens and workers of five bumblebee (Bombus Latr.) species and by inverted workers scraping pollen from anthers concealed within the corolla galea. The nectarless, rostrate flowers of P. contorta, P. groenlandica, P. ornithorhyncha, and P. racemosa were pollinated by pollen‐foraging workers and occasional queens virbrating pollen from concealed anthers. Insect exclosure methods revealed complete absence of fruiting in the absence of insects, and pollinator collections further indicate obligate dependence of the plants upon bumblebees for their sexual reproduction. Analysis of corbicular pollen loads from pollinators suggested that pollinator species are not monolectic but that individual pollinators range from monolectic to polylectic. Measurements indicated limited correlations between lengths of corolla tubes and tongues of nectar‐foraging insects. Each nectarless Pedicularis species occupied a different, specific habitat, but P. bracteosa and the endemic P. rainierensis were sympatric in part. Each species had a unique spectral reflectance pattern from the corolla. Proximity of habitats and overlap of blooming periods of all Pedicularis species eliminate the possibility of contemporary geographic or phenological reproductive isolation. It is suggested that behavioral interactions of the plants and their insect pollinators may have been instrumental in the past in reproductively isolating these species, hybrids of which are unknown.
CELL ARREST IN Gl AND G2 OF THE MITOTIC CYCLE OF VICIA FABA ROOT MERISTEMS
Authors: Hof J. Van't , Hoppin D. P. , Yagi S.
Published: January 2018

Experiments were performed with cultured excised primary root tips of Vicia faba ‘Longpod’ to determine: (1) the proportion of meristematic cells arrested in Gl and in G2 during carbohydrate starvation, and to determine if the proportion is fixed or can be varied experimentally; (2) the effect of increased starvation on the ability of arrested cells in Gl and G2 to initiate DNA synthesis and mitosis, respectively, when exogenous sucrose was supplied; and (3) whether puromycin, cycloheximide, or actinomycin D prevented the initiation of DNA synthesis and the onset of mitosis. Microspectrophotometry of nuclear DNA and autoradiographic measurements of incorporated 3H‐thymidine showed that 72 hr of starvation immediately after excision produced tissue with more than 70 % of the cells arrested in G2 and less than 30 % in Gl. If cultured for three days and then starved for 72 hr, the tissue had nearly equal numbers of cells arrested in Gl and G2. As the duration of starvation increased, the time required to initiate DNA synthesis and to divide when carbohydrate was replenished also increased. Inhibition of protein synthesis by puromycin and cycloheximide prevented the initiation of DNA synthesis and mitosis, but actinomycin D, an inhibitor of RNA synthesis, did not prevent division of cells from G2 nor DNA synthesis by cells from Gl. The experiments demonstrated that the mitotic cycle of Vicia has two major controls, one in Gl and another in G2, and that other factors determine how many cells are affected by either of these cycle controls.
THE TIME‐COURSE OF POLAR MOVEMENT OF GIBBERELLIN THROUGH ZEA ROOTS
Authors: Jacobs W. P. , Pruett Paula E.
Published: January 2018

The polarity of movement of gibberellin through sections cut from near the root tips of Zea mays L. was studied, using methods like those we previously used in roots for auxin and in petioles for auxins, cytokinins, and gibberellic acid (GA‐3). One μg GA‐3 was added in a donor agar block and gibberellin activity in the receiver agar at the opposite end of the section was measured directly with a modified barley endosperm bioassay. The movement of gibberellin was away from the root tip (basipetal) and thus opposite in direction to the polarity of auxin through such root sections. The time‐course of basipetal movement was dissimilar to that for gibberellin or auxin movement through petiole sections. It took 14‐18 hr for gibberellin activity equivalent to 6 ng GA‐3 to collect in the basal receivers on roots. Apical receivers showed activity equivalent to 1.6 ng GA‐3 at 14‐18 hr. Less than 0.01 ng equivalent GA‐3 was collected from sections to which GA‐3 was not added, so the 6 and 1.6 ng were almost entirely due to the added GA‐3. These general conclusions were confirmed with an experiment using 14C‐GA‐3. A decline in activity in receivers was found in some experiments at 18 hr, paralleling earlier results with GA‐3, IAA, and adenine in petioles and IAA in roots.
THE AFFINITY OF ONION CELL WALLS FOR CALCIUM IONS
Authors: Somers G. Fred
Published: January 2018

Cell walls prepared from onion bulbs were found to exhibit an affinity for Ca++. The adsorption of this ion was enhanced by the action of pectin methylesterase. It was confirmed that Ca++ reacts with two COO“ groups and the corresponding affinity constant, K, was found to be: log K = 4.25. The action of pectin methylesterase had no effect upon K. The cell walls, as prepared, had 25 % of the total COO− groups occupied by Ca++, 14 % by Mg++, and 39 % by H+. Treatment with acidified ethanol removed all of the metallic cations. K+ and Mg++ could displace Ca++ from the cell walls. At concentrations from 10−3 to 3 times 10−3 m it required from 4.9 to 13.2 moles of Mg++ to displace one mole of Ca++. For K+ it required 80 moles to displace 1 mole of Ca++ at K+ concentrations from 0.65 × 10−2 to 1.6 × 10−2 M.
ALTITUDINAL VARIATION IN HAWAIIAN METROSIDEROS
Authors: Corn Carolyn A. , Hiesey William M.
Published: January 2018

Hawaiian Metrosideros is a highly polymorphic complex that is distributed throughout the six major islands of the Hawaiian Island chain from tropical climates near sea level to altitudes up to 8,500 ft with frost. Its populations extend continuously over many areas with average annual precipitation ranging from 30 to 450 in. and with diverse edaphic and topographical features. The Hawaiian forms are probably all derived from one or a very small number of ancestral introductions that arrived within the last 20 million years by longdistance dispersal. Seeds collected from diverse altitudinal sites on the islands of Hawaii and Maui and grown under uniform greenhouse conditions at Honolulu show evidence of ecotypic differentiation along altitudinal gradients. Seedlings from these islands separated by 50 miles of ocean show parallelism in their altitudinal differentiation in plant height and leaf size, but with strongly overlapping variation from site to site.
REPRODUCTIVE BIOLOGY OF WEEDY AND CULTIVATED MIRABILIS (NYCTAGINACEAE)
Authors: Cruden Robert William
Published: January 2018

The reproductive biology of Mirabilis nyctaginea (Michx.) MacM. contributes to the plant's success as a weed and invader of disturbed habitats whereas that of M. Jalapa L. reflects its success as a cultivar. Plants of M. nyctaginea flowering in early summer produce chasmogamous flowers whereas plants flowering in late summer produce cleistogamous flowers. Plants of both species are self‐compatible and flower behavior contributes to self‐pollination. The flowers open late in the afternoon and close late the following morning. In M. nyctaginea flowers are effectively pollinated by bees both in the afternoon and morning, and during the night moths are effective pollinators. Mirabilis Jalapa is self‐pollinating. Anther closure during rain showers, a result of water droplets falling into open anthers, minimizes pollen loss and is highly adaptive. The reproductive biology of M. nyctaginea and M. Jalapa is contrasted with that of the obligate outcrossing species M. multiflora (Torr.) Gray and M. froebelii (Behr) Greene.
SUCROSE‐INDOLE‐3‐ACETIC ACID INTERACTIONS ON ROOT REGENERATION BY PINUS LAMBERTIANA EMBRYO CUTTINGS
Authors: Greenwood Michael S. , Berlyn Graeme P.
Published: January 2018

Interactions affecting root formation by IAA and sucrose, supplied to Pinus lambertiana embryo cuttings through their cotyledons, were explored. The sucrose optimum for rooting and dry weight increase is approximately 8 %. Osmotic substitutes for sucrose, applied alone or concomitantly with sucrose, were unable to duplicate its effects on regeneration. One μM IAA increased the number of roots per cutting with all sucrose concentrations. However, with suboptimal sucrose concentrations it only increased the total number of cuttings forming roots. Because IAA accumulates at the site of root formation, the possibility that it mobilizes sucrose or its derivatives to the site of root formation was explored. No evidence was found for hormone‐directed transport of sucrose in this system. IAA had no effect on either the basal accumulation or transport of label derived from U‐14C‐sucrose.
IDENTIFICATION OF THE GENOMIC COMPLEMENTS OF EMILIA PRAETERMISSA (SENECIONEAE—COMPOSITAE)
Authors: Olorode Omotoye
Published: January 2018

Statistical tests show that the ten large chromosomes of Emilia praetermissa Milne‐Redhead were derived from E. coccinea (Sims) G. Don while the remaining ten small chromosomes of E. praetermissa were derived from E. sonchifolia (L.) DC. It is shown too that mean length of chromosomes is smaller and more variable among the cells of diploids (species and hybrids) than of tetraploids. The nature and probable mechanisms of control of size differences among the complements are discussed.
DIFFERENCES IN NITROGEN REQUIREMENTS OF TWO CLONES OF CONVOLVULUS ARVENSIS IN VITRO
Authors: Harvey R. G. , Muzik T. J. , Warner R. L.
Published: January 2018

Various nitrogen sources were shown to alter the growth and modify nitrate reductase activities of stem callus tissue derived from two clones of Convolvulus arvensis L. (field bindweed). Callus from a Washington (S) clone grew better and had a higher level of nitrate reductase activity than callus from a New Mexico (R) clone when nitrate was the only source of nitrogen available in the culture medium. The addition of glycine to the culture medium decreased growth of the R clone and increased growth of the S clone, but glutamic acid repressed growth of both clones. An amide source of nitrogen such as glutamine or asparagine, or ammonium was required to produce maximum growth of both bindweed clones. Glutamine increased nitrate reductase activity in the two clones, and glycine increased nitrate reductase activity in the S clone but decreased it in the R clone. Glutamic acid decreased nitrate reductase activities in both the R and S tissues.
RECONSTITUTION OF A MEMBRANE‐LIKE STRUCTURE WITH STRUCTURAL PROTEINS AND LIPIDS ISOLATED FROM TOBACCO THYLAKOID MEMBRANES
Authors: Huang Jeng‐sheng , Huang Pi‐yu , Goodman Robert N.
Published: January 2018

Structural proteins and lipids were extracted from thylakoid membranes and were dissolved separately with sodium dodecyl sulfate. Dissolved structural proteins reaggregated into spherical clumps, and lipids into globules composed of alternating light and dark bands, upon dialysis against dilute beta‐buffer containing 20 mM Mg++. The reaggregates of the mixture of structural proteins and lipids formed membranous structures. The appearance and thickness of the reconstituted membranes are similar to those of thylakoid membranes prepared from sonicated chloroplasts.
DEVELOPMENTAL ANATOMY OF EPIDERMAL AND MESOPHYLL CHLOROPLASTS IN OPUNTIA BASILARIS LEAVES
Authors: Freeman Thomas P.
Published: January 2018

Developmental studies of Opuntia basilaris Engelm. & Bigel. leaves revealed the presence of three morphologically distinct types of plastids. All epidermal cells examined contained chloroplasts. After 13 days of growth in the dark the plastids of epidermal and mesophyll cells were characterized by the presence of a prolamellar body and fibril inclusions. Epidermal plastids which developed under light conditions contained large stromacentres and a limited grana‐fret membrane system. Guard cell plastids developed under similar conditions had a much poorer developed grana system with fibril inclusions apparent only during the developmental stages. At maturity these plastids appeared swollen or dilated. Mesophyll plastids had fibril inclusions during all stages of development and at maturity contained a very extensive grana‐fret membrane system. Microbodies were found in association with the mesophyll plastids. Starch accumulation was common in subsidiary cell and guard cell plastids.
GENETIC LOAD IN OSMUNDA REGALIS POPULATIONS
Authors: Klekowski Edward J.
Published: January 2018

Osmunda regalis sporophytes form haploid spores which develop into functionally hermaphroditic gametophytes. The self‐fertilization of such gametophytes results in zygotes which are completely homozygous. Spore samples collected from sporophytes in natural populations were used to establish gametophyte cultures. The majority of these gametophytes were unable to form viable embryos when only self‐fertilization was possible. Controlled selfing and crossing experiments revealed that the inability of these homozygous embryos to develop normally is attributable to the presence of recessive lethals. To account for this genetic load, an hypothesis is proposed integrating the morphology and ecology of the gametophyte generation with the polyploid genetic system of the sporophyte generation.
RADIOSENSITIVITY, RNA, AND PROTEIN METABOLISM OF “LEAKY” AND ARRESTED CELLS IN SUNFLOWER ROOT MERISTEMS (HELIANTHUS ANNUUS)
Authors: Rost T. L. , Hof J. Van't
Published: January 2018

Two cell populations in sunflower root meristems are described. Most cells stop in G1 after being cultured in sucrose‐deficient medium, but “leaky” cells continue through DNA synthesis and stop in G2. A comparison of “leaky” and arrested cells is reported on the basis of radiosensitivity, and cytological and biochemical responses to metabolic inhibitors. “Leaky” cells are randomly distributed throughout primary meristematic tissues. They are not inhibited from initiating DNA synthesis by exposure to doses of γ‐irradiation ranging from 300–7200 R; arrested cells, depending upon the dose, are inhibited partially or completely. “Leaky” cells do, however, show a dose‐dependent mitotic delay in G2, which is the same as arrested cells. Treatment with puromycin and actidione does not inhibit “leaky” cells from initiating DNA synthesis but does inhibit them from mitosis. Arrested cells are inhibited from advancing to S and M by both inhibitors. Also, puromycin and actidione cause a decrease in protein and RNA synthesis, demonstrating a possible protein dependent RNA synthesis necessary for cell cycle progression. Actinomycin D (10 μg/ml) inhibits neither “leaky” nor arrested cells from entering S and M. At 30 μg/ml, however, arrested cells are partially inhibited. “Leaky” cell metabolism is unique in preparation for and initiation of DNA synthesis but similar to that of the remaining cells of the meristem in terms of requirements for progression through the rest of the mitotic cycle.
ENTOMOPHILOUS, INTRAFLORAL POLLINATION IN PHYLA INCISA
Authors: Estes James R. , Brown Linda S.
Published: January 2018

Experimental pollination studies indicate that probing into the corolla tube by insects is a requirement for autogamous reproduction in Phyla incisa. Insect‐mediated self‐fertilization combines the anthecology of allogamous reproduction with the genetic consequences of autogamy.
ULTRASTRUCTURE OF THE SECRETORY DUCTS OF RHUS GLABRA L.
Authors: Fahn Abraham , Evert Ray F.
Published: January 2018

The infrastructure and development of the secretory ducts were studied in the secondary phloem of Rhus glabra L. The ducts were found to develop schizogenously. The electron microscope observations may explain the view of several previous authors of schizo‐lysigenous development of the duct lumen in the Anacardiaceae. The secreted material consists of lipophilic and polysaccharide substances. The electron micrographs suggest that the lipophilic substances arise in plastids, ER cisternae, Golgi vesicles, and mitochondria. The polysaccharide constituents apparently originate from the outer wall layers of the epithelial cells. The wall layers facing the lumen of the duct disintegrate and form, together with the secreted osmiophilic droplets, the gum‐resin. Numerous microtubules were found along walls of the epithelial cells.
COMPETITION AND ACCOMMODATION BETWEEN APICAL LAYERS AND THEIR DERIVATIVES IN THE ONTOGENY OF CHIMERAL SHOOTS OF PELARGONIUM X HORTORUM
Authors: Stewart R. N. , Semeniuk Pete , Dermen Haig
Published: January 2018

Two mutant plastogenes in all possible chimeral combinations were followed in Pelargonium X hortorum Bailey (geranium) shoots. The part of stem, leaf, or other structure derived from each apical layer was clearly apparent on a cell to cell basis. Shoots typically were composed of derivatives of three apical layers but we found derivatives of as many as four apical layers in some leaves and of five layers in some stems. In chimeras with one of the mutants, Dpl W1, the amount of tissue derived from the various apical layers was the same, whether the layer was mutant or wild type. We suggest that there are independent apical layers and cell lineages derived from them in nonchimeral shoots, and that their contribution in normal ontogeny is like that of the layers in Dpl W1 chimeras. In chimeras carrying the second mutant, Dpl W2, there was much less tissue derived from mutant than from wild‐type apical layers. The phenotypic expression of the plastogenes was unchanged by their transmission through male or female gametes. Comparisons of the ontogeny of geranium plants carrying the W1 or W2 mutant suggested that, while there was competition between the apical layers and between their derivatives, the genome imposed a definite harmonious interaction or accommodation which led to a final normal morphology of all plant parts and organs through quite different ontogenetic pathways.
STRUCTURE AND DEVELOPMENT OF THE SIEVE ELEMENT IN THE STEM OF LYCOPODIUM LUCIDULUM
Authors: Warmbrodt Robert D. , Evert Ray F.
Published: January 2018

Stem tissue of Lycopodium lucidulum Michx. was fixed in glutaraldehyde and postfixed in osmium tetroxide for electron microscopy. Although their protoplasts contain similar components, immature sieve elements can be distinguished from parenchymatous elements of the phloem at an early stage by their thick walls and correspondingly high population of dictyosomes and dictyosome vesicles. Late in maturation the sieve‐element walls undergo a reduction in thickness, apparently due to an “erosion” or hydrolysis of wall material. At maturity, the plasmalemma‐lined sieve elements contain plastids with a system of much convoluted inner membranes, mitochondria, and remnants of nuclei. Although the endoplasmic reticulum (ER) in most mature sieve elements was vesiculate, in the better preserved ones the ER formed a tubular network closely appressed to the plasmalemma. The sieve elements lack refractive spherules and P‐protein. The protoplasts of contiguous sieve elements are connected with one another by pores of variable diameter, aggregated in sieve areas. As there is no consistent difference between pore size in end and lateral walls these elements are considered as sieve cells.
THE OCCURRENCE OF “ROOT GAPS” IN THE RHIZOME SOLENOSTELE AND LEAF TRACE OF DENNSTAEDTIA CICUTARIA
Authors: Stevenson Dennis Wm.
Published: January 2018

The vascular system of the rhizome axes of Dennstaedtia cicutaria consists of a solenostele with an amphicribral vascular bundle centrally located in the pith. Each leaf has a single trace which is an amphicribral vascular bundle. At each node of an axis there is a complex consisting of the main axis, leaf base, and a branch axis attached to the basiscopic margin of the leaf base. Numerous roots are present on the rhizomes and the abaxial side of the leaf bases. Parenchymatous gaps occur in the rhizome solenostele and the leaf trace directly above the departure of some of the root traces. These gaps are termed root gaps. In some instances the root gaps are confluent. However, not all of the root traces have an associated root gap. The leaf trace is inserted laterally on the main and branch axes at the node so that the acroscopic leaf trace margin anastomoses with the main axis of the vascular system and the basiscopic margin with that of the branch axis. Two leaf gaps are associated with each leaf trace, one occurring in the main axis solenostele and the other in the branch axis solenostele. The medullary bundle of each axis anastomoses with each leaf trace at its point of attachment to the rhizome solenostele. Thus, the medullary bundle forms a continuous vascular strand from leaf trace to leaf trace in any given rhizome axis.
FINE STRUCTURE OF THE SPERMATOZOID OF ZAMIA: THE VIERERGRUPPE
Authors: Norstog Knut
Published: January 2018

The spermatozoids of Zamia integrifolia were examined by electron microscopy in order to clarify the structure of a fibrous organelle underlying the flagellar basal bodies. The ultrastructure of this organelle was found to resemble one similar in organization occurring in Marchantia spermatozoids and termed the Vierergruppe. Therefore the term is extended to include this structure in the Zamia spermatozoid. The Vierergruppe of Zamia is interpreted as composed of an upper (distal) layer of keeled microtubules and a lower (proximal) layer of vertical fins with lateral processes that give a three‐layered appearance to this component.
COMPARATIVE STUDIES OF THE NODAL AND VASCULAR ANATOMY IN THE NEOTROPICAL CYATHEACEAE. II. SQUAMATE GENERA
Authors: Lucansky Terry W.
Published: January 2018

Vascular tissue development in the mature stems of the six squamate genera (those with scales as stem and petiole indument) of the Cyatheaceae is described. All squamate genera possess an erect stem, although Cnemidaria approaches an acaulescent condition. The majority of the species studied possesses a spiral phyllotaxy, although a whorled condition predominates in certain species. Adventitious roots arise from the leaf bases and, at irregular intervals, from the stem. Adventitious buds occur in the genera Alsophila and Nephelea and show the same ontogenetic changes as occur in the young sporophytes of tree ferns. Mature stems have a dictyostele with overlapping leaf gaps; this consists of individual meristeles, each surrounded by sclerenchymatous tissue. All genera possess medullary bundles, whereas cortical bundles are found only in certain genera and species. The origin, course, and function of these accessory vascular bundles are discussed. The squamate genera in the Cyatheaceae show striking similarities in both anatomical and morphological characters, and constitute a natural grouping.
COMPARISON OF SEED PROTEINS IN THE GENUS SUAEDA (CHENOPODIACEAE) BY MEANS OF DISC GEL ELECTROPHORESIS
Authors: Ungar Irwin A. , Boucaud J.
Published: January 2018

Polyacrylamide gel disc electrophoresis was utilized to determine seed protein patterns in ten taxa within the genus Suaeda. The results indicated a close relationship, averaging 92.2 %, similarity between the seed protein patterns of S. maritima var. macrocarpa, S. maritima var. vulgaris, and S. maritima var. flexilis. These intraspecific forms were more similar to one another than to any of the other taxa investigated. A continental North American species, S. depressa, was related to the S. maritima complex, and its protein pattern indicates that it may have evolved from S. maritima. The technique of disc electrophoresis proved useful in assessing the degree of similarity between taxa within the genus Suaeda.
NEW FERTILE SPECIES OF PSILOPHYTON FROM THE DEVONIAN OF MAINE
Authors: Kasper Andrew E. , Andrews Henry N. , Forbes William H.
Published: January 2018

A review of the history of the genus Psilophyton is presented. Two new species with sporangia in organic connection, P. microspinosum and P. dapsile, are described. They are compared with Psilophyton‐like plants from Maine and other previously described fertile species of this genus. Evidence from several species in the Trout Valley flora confirms the concept of this taxon as presented by Hueber and Banks. Data based on all sporangium‐bearing species of Psilophyton are outlined, certain evolutionary trends within the taxon are tentatively presented, and recommendations for the treatment of the numerous fragmentary species and future new species are suggested.
COMPARATIVE MEASUREMENTS OF NUCLEAR DNA IN A HETEROTHALLIC AND A SELF‐FERTILE ISOLATE OF THE MYXOMYCETE, DIDYMIUM IRIDIS
Authors: Therrien C. D. , Yemma John J.
Published: January 2018

Comparative measurements were made of the nuclear Feulgen‐DNA content of a heterothallic and a self‐fertile isolate of the myxomycete Didymium iridis. Plasmodial nuclei of both isolates contain the diploid amount of DNA. The replicated diploid (4C) values for the heterothallic and the self‐fertile isolates are 5.66 and 5.95, respectively. Myxamoebae, however, are quite dissimilar in their nuclear DNA content. Those of the heterothallic isolates, Honduran 1–2 (A1) and Panamanian 2–4 (A7), have mean values of 3.81 and 3.69, whereas myxamoebae of the self‐fertile Philippine‐1 isolate were found to have a mean value of 6.07. Myxamoebae of the Ph‐1 isolate are, therefore, at the same ploidy level as the Ph‐1 Plasmodium. Mean DNA values for Ph‐1 sporangial nuclei were in category 4C. Measurement of the DNA content of mitotic metaphases in sporangia at T = 6 hr confirmed that the mean DNA content of both Ph‐1 myxamoebae and plasmodial nuclei is equivalent to 4C. It is concluded that nuclear phase alternance is lacking in the Ph‐1 isolate and that the Plasmodium of this isolate develops by apogamy.
CHROMOSOME NUMBERS IN COMPOSITAE. IX. HAPLOPAPPUS AND OTHER ASTEREAE
Authors: Anderson Loran C. , Kyhos Donald W. , Mosquin Theodore , Powell A. Michael , Raven Peter H.
Published: January 2018

Reports of 209 original chromosome counts are made for the tribe Astereae of Compositae, including first counts for two genera and 46 species or subspecies. With over 80 % of the species counted, chromosome numbers are now available for all North American sections of Haplopappus. Two major groupings are apparent: one, with basic numbers of x = 4, 5, or 6, is basically herbaceous; the other, with x = 9, consists of shrubs or subshrubs. Aneuploidy is known only in the “herbaceous” group of Haplopappus, and polyploidy is more extensive there than in the woodier group of sections.
THE ULTRASTRUCTURE OF THE ROOT CAP IN CULTURED ROOTS OF CONVOLVULUS ARVENSIS L.
Authors: Phillips Harry L. , Torrey John G.
Published: January 2018

The ultrastructure of root cap cells of cultured roots of Convolvulus arvensis L. was studied in order to relate sequential changes in the fine structure with known changes in morphology and physiology determined earlier by light microscopy and autoradiography. The rapid structural changes observed in columella cells formed from the root cap initials distal to the quiescent center can be related to the function of these cells as sensors of geotropic stimuli. Even more rapid structural changes in cells of the root cap periphery can be ascribed a functional role in protecting the columella and initial cells as the root is displaced through the soil. Mechanisms are discussed whereby cell division and differentiation in the root apex may be controlled by hormones in the apex.
CHROMOSOME NUMBERS IN COMPOSITAE. X.
Authors: Powell A. Michael , Kyhos Donald W. , Raven Peter H.
Published: January 2018

Reports of 126 new counts are recorded for 9 tribes of Compositae, including reports for 45 genera and 102 species. Six genera, Psilocarphus (n = 14). Relhania (n = 7), Rutidosis (n = 9), Chaetanthera (n = 14), Hecastocleis (n = 8), and Hesperomannia (n = 10), and 41 species were previously unreported.
FLORAL BIOLOGY OF MAGNOLIA
Authors: Thien Leonard B.
Published: January 2018

The floral biology of eight species of Magnolia native to the United States is described. The flowers are protogynous. They are pollinated by several species of beetles that enter buds as well as closed and open flowers to feed on nectar, stigmas, pollen, and secretions of the petals. Individual flowers persist from two to four days and undergo a series of petal, stigma, and stamen movements that assure pollination by beetles. It is suggested that the flowers of Magnolia are highly specialized for exclusive pollination by beetles. These specialization mechanisms produce large quantities of food for the beetles and deny other types of insects (bees, moths, etc.) access to the flowers at critical stages in the pollination process, i.e., when stigmas are mature and pollen is shed.
FERTILIZATION IN OEDOGONIUM. III. KARYOGAMY
Authors: Hoffman Larry R.
Published: January 2018

Karyogamy is described in Oedogonium cardiacum from ultrastructural studies. Close proximity of the two gamete nuclei in the fusion cell is established by plasmogamy, whereas karyogamy appears to be initiated by multiple contacts formed between the outer membranes of the adjoining nuclear envelopes. Blebs of endoplasmic reticulum (ER) originate from the outer membrane of each nuclear envelope; these ER blebs presumably contact and fuse with the outer membrane of the nuclear envelope of the opposing nucleus. This is followed by the fusion of the inner membranes of the opposing nuclear envelopes, thereby resulting in a series of small connective bridges between the two gamete nuclei. It is estimated that in this manner 30–50 bridges are formed, perhaps many more. Several of these bridges enlarge relative to the others; one presumably becomes the major connection between the fusing nuclei. As it continues to enlarge, any organelles positioned between the fusing nuclei are pushed aside. There is also evidence, particularly in later stages of karyogamy, that the smaller connective bridges fuse to form larger ones. Temporary cytoplasmic channels often result at the juncture of fusion. In other instances, isolated inclusions of cytoplasm may be delimited by remnants of nuclear envelope deep within the developing zygote nucleus; these inclusions disappear with subsequent development. Throughout karyogamy the contribution of the male gamete nucleus is readily recognized by the characteristic appearance of its highly condensed chromatin. Ultimately, however, this distinction is lost and the content of the mature zygote nucleus assumes a more uniform appearance very similar to that of an egg nucleus. The complete process of fertilization in Oedogonium may occur within 15 min of mixing the spermatozoids with eggs.
THE POLLINATION ECOLOGY OF PEDICULARIS (SCROPHULARIACEAE) IN THE YUKON TERRITORY
Authors: Macior Lazarus Walter
Published: January 2018

The pollination ecology of six native species of Pedicularis (Scrophulariaceae) was investigated in the Kluane Range of the St. Elias Mountains in the Yukon Territory (Canada). Seed production in all species depended upon pollination by bumblebees (Bombus Latr. spp.). Asexual propagation by root and crown branching was present in P. capitata and P. langsdorfii. Cinematographic and stereophotographic records indicated that bumblebee queens foraged in an upright (nototribic) position for nectar and pollen. Bombus workers foraged upright on P. verticillata, inverted (sternotribic) on P. labradorica, and in both positions on P. capitata, P. kanei, P. langsdorfii, and P. sudetica. The potential for hybridization between Pedicularis species by reason of overlapping blooming periods, sharing of the same or adjacent habitats, and recovery of individually marked pollinators was noted. Analysis of 1402 corbicular pollen loads from 1769 pollinating bumblebees of 14 species of Bombus on Pedicularis revealed that equal numbers of pure and mixed loads were collected. This suggested a low level of forager fidelity to a single plant species. Investigation of colors of corollas in visible light by reflectance spectrophotometry and in long‐wave (360 nm) ultraviolet light by photography revealed distinct reflectance spectra for visible light but no ultraviolet reflectance. A wide range of concentrations of sugar in nectars from the six species of Pedicularis was detected by refractometry. Chromatographic analysis of nectars indicated fructose and sucrose in nectars of four species with P. kanei and P. langsdorfii having additional glucose and raffinose or glucose and rhamnose, respectively. Nectar was abundant in all species except P. labradorica. A comparison of lengths of nectariferous tubes of corollas, lengths of tongues (prementum plus glossa) of pollinators, behavior of pollinators, and diversity of species of pollinators on each species of Pedicularis indicated that adaptive behavior of pollinators was related to the length of tongues of pollinators. It is suggested that interactions between floral mechanisms and pollinating insects probably contributed substantially to the present diversity of floral form in species of Pedicularis in North America.
CHROMOSOME NUMBERS IN COMPOSITAE. XI. HELENIEAE
Authors: Powell A. Michael , Kyhos Donald W. , Raven Peter H.
Published: January 2018

Reports of 89 new counts are recorded for the tribe Helenieae, including reports for 28 genera and 56 species. One genus, Hypericophyllum (n = 9), and six other taxa were previously unreported.
EFFECT OF STRATIFICATION TEMPERATURE AND GERMINATION TEMPERATURE ON GERMINATION AND THE INDUCTION OF SECONDARY DORMANCY IN COMMON RAGWEED SEEDS
Authors: Willemsen Roger W.
Published: January 2018

Stratification of common ragweed (Ambrosia artemisiifolia) seeds at 4 C was most successful for breaking dormancy, whereas ‐5 C was least effective and 10 C was intermediate. Germination in the light exceeded that in the dark at all stratification and germination temperatures. The optimum temperatures for germination in the light were 10/20, 15/25, and 20/30. Maximum germination in the dark occurred at 20/30 C for seeds stratified at 4 and 10 C but the optimum temperatures for seeds stratified at ‐5 C were 10/20, 15/25, and 20/30. Seeds stratified at ‐5 and 10 C germinated best after 15 weeks of stratification, whereas 12 weeks of stratification at 4 C resulted in maximum germination. Secondary dormancy was induced in seeds which did not germinate in the dark. This was affected by stratification temperature and duration and germination temperature. The ecological significance of these germination characteristics is discussed.