bluuebunny/crossref_metadata_2025 huggingface dataset:
DNA SYNTHESIS AND MITOSIS IN MERISTEMS: REQUIREMENTS FOR RNA AND PROTEIN SYNTHESIS
Authors: Webster P. L. , Hof J. Van't
Published: January 2018

Following provision of sucrose to starved, stationary phase pea root meristems, G1 and G2 cells enter DNA synthesis and mitosis, respectively. Puromycin (450 μg/ml) and cycloheximide (5 μg/ml) completely prevent this initiation of progression through the cell cycle. Actinomycin D (10 μg/ml) has no effect on the initial entry of G1 and G2 cells into S and mitosis, although later entry is prevented. The resistance of the cells to actinomycin D is lost slowly with time in medium without sucrose, suggesting that an RNA required for the resumption of proliferative activity is being gradually lost. The effects of the inhibitors on transitional and proliferative phase meristem cells indicate that such dividing cells do indeed have sufficient of the requisite RNA for 8‐12 hr progression through the cycle, but that protein synthesis is required continuously. It is suggested that this RNA is the one lost slowly during starvation, allowing starved cells to reinitiate progression through the cycle in the presence of actinomycin D.
HELICOCYTIC AND ALLELOCYTIC STOMATA: UNRECOGNIZED PATTERNS IN THE DI COTYLEDON AE
Authors: Payne Willard W.
Published: January 2018

Two new mesogenous stomatal patterns are described for the Dicotyledonae: helicocytic, with a helix of four or more subsidiary cells surrounding the guard cell pair, and allelocytic, with an alternating complex of three or more C‐shaped subsidiary cells of graded sizes. The latter pattern may have guard cells developed parallel to the subsidiary cells (parallelocytic) or at right angles to them (diallelocytic). For both types, the complex development of regular sequences of mesogene subsidiary cells with particular attributes of size and arrangement provides strong probability of correlated ontogeny and adult pattern. They are related to mesogenous forms of the anisocytic, paracytic and diacytic patterns, but these latter may also be developed in different ways. The use of stomatal pattern data for taxonomic and evolutionary studies of dicote is discussed.
ISOENZYME COMPLEMENTS OF DIANTHUS CALLUS CULTURES: INFLUENCE OF LIGHT AND TEMPERATURE
Authors: McCown B. H. , McCown D. D. , Beck G. E. , Hall T. C
Published: January 2018

Callus cultures isolated from the stems of two clones of Dianthus were extracted for water‐soluble proteins and the extracts were subsequently analyzed by acrylamide gel electrophoresis. Peroxidase, acid phosphatase, esterase, and 6‐P‐gluconate dehydrogenase (6‐P‐G DH) were studied under each of four combinations of light and dark, cold (0‐5 C) and warm (25 C) environments. Marked differences in the isoenzyme patterns were observed under the four conditions with all the enzymes except 6‐P‐G DH. Acid phosphatase generally showed fewer isoenzymes than the usual stem complement, whereas the other enzymes showed the same or greater number of isoenzymes. Many of the isoenzymes from the callus tissue correlated well with those found in the stem; however, all but 6‐P‐G DH showed some different components. Of the four enzymes studied only peroxidase was recovered from the medium; these isoenzymes matched those found in the callus and in the stem. The isoenzymes in the medium were not influenced qualitatively by the growth conditions. The changes in the zymograms of the callus under the four environments were compared to the changes observed in the stem under stress environments.
ONTOGENETIC ANALYSIS OF TREE ROOTS IN ACER RUBRUM AND BETULA PAPYRIFERA
Authors: Wilson Brayton F. , Horsley Stephen B.
Published: January 2018

The development of long (6‐20 m) tree roots was reconstructed from serial transverse sections taken 10‐20 cm apart. Measurements of primary xylem diameter showed that the tips of long roots of red maple (Acer rubrum L.) and paper birch (Betula papyrifera Marsh.) are initially small, but they increase in diameter with increasing distance from the stem. A repeating pattern of the width of the first annual ring marks length increments of long roots. The pattern of ring width is paralleled by a pattern of primary xylem diameter. Our interpretation is that primary xylem diameter increases during spring and early summer, stays constant during late summer and decreases in autumn. After injuries to large root tips, new large lateral tips are formed that replace the parent tip. Thus, a single long root is actually formed by a succession of these replacement roots. In a series of sections there may be sudden changes in primary xylem diameter as the successive sections pass from parent root to replacement root at points of injury. These changes in birch are associated with changes in a number of protoxylem poles.
NUCLEAR BEHAVIOR IN THE BASIDIOMYCETE, VOLVARIELLA VOLVACEA
Authors: Chang Shu‐Ting , Ling Kit‐Yin
Published: January 2018

The basidiospores of the straw mushroom are typically uninucleate and its vegetative hyphae are generally multinucleate. There is a marked reduction of nuclear number in the trama and subhymenium. Interphase nuclei exist in two forms, each of which undertakes a particular mode of division. The “diffused” nuclei divide by conventional mitosis while the “constricted” ones divide amitotically. In metaphase of mitosis nine chromosomes were seen both in polar and lateral view. This haploid number confirms the nine bivalents found in basidia during meiosis. A unique characteristic of this fungus is that the diploid nucleus, the two postkaryotic nuclei and the four postkaryotic nuclei may be enclosed by a well‐defined nuclear envelope during division.
FURTHER ANALYSIS OF OENOTHERA BIENNIS POPULATIONS FOR INCOMPATIBILITY ALLELES
Authors: Khafaji Sadiq D. Al , Steiner Erich
Published: January 2018

The complex‐heterozygotes of Oenothera biennis are characterized by an incompatibility allele system which acts as a part of the balanced lethal mechanism. A survey was made to determine the number and frequency of different incompatibility alleles in populations throughout south central Ohio and Indiana and in one population in northern Kentucky. No single population was found to possess more than two different alleles. Within the geographic area specified, however, at least eight different alleles occurred among the various population samples. If the incompatibility alleles are a valid index of variability for the complexes which carry them, these results suggest that individual populations are fairly uniform genetically and probably arise from relatively few colonizers. The various alleles found in these populations are believed to be relics of structurally homozygous self‐incompatible progenitors which hybridized with structurally homozygous, but segmentally distinctive, self‐compatible forms to give rise to the complex‐heterozygotes.
CHROMOSOME MORPHOLOGY IN THE GENUS SAMBUCUS
Authors: Ourecky Donald K.
Published: January 2018

Two basic chromosome karyotypes were found in the genus Sambucus. Chromosome numbers were observed to be 2n = 38 for S. callicarpa, S. cerulea, S. glauca, S. kamtschatica, S. melanocarpa, S. mexicana, S. miquelli, S. sibirica, and S. sieboldiana and 2n = 36 for S. simpsonii and S. williamsii. Measurements of 18 karyotypes are presented. The major differences between the two basic chromosome karyotypes can be explained as the result of a mis‐division of a metacentric chromosome giving rise to two telocentric chromosomes, thus reducing the number of metacentrics from five to four and increasing the chromosome number from 2n = 36 to 2n = 38. Observed chromosome aberrations and aneuploidy may result from unstable telocentric chromosomes.
AN ULTRASTRUCTURAL BASIS FOR HYPHAL TIP GROWTH IN PYTHIUM ULTIMUM
Authors: Grove S. N. , Bracker C. E. , Morré D. J.
Published: January 2018

Hyphae of the fungus Pythium ultimum extend by tip growth. The use of surface markers demonstrates that cell expansion is limited to the curved portion of the hyphal apex. Growing and non‐growing regions are reflected in internal organization as detected by light and electron microscopy. The young hypha consists of three regions: an apical zone, a subapical zone and a zone of vacuolation. The apical zone is characterized by an accumulation of cytoplasmic vesicles, often to the exclusion of other organelles and ribosomes. Vesicle membranes are occasionally continuous with plasma membrane. The subapical zone is non‐vacuolate and rich in a variety of protoplasmic components. Dictyosomes are positioned adjacent to endoplasmic reticulum or nuclear envelope, and vesicles occur at the peripheries of dictyosomes. A pattern of secretory vesicle formation by dictyosomes is described which accounts for the formation of hyphal tip vesicles. Farther from the hyphal apex the subapical zone merges into the zone of vacuolation. As hyphae age vacuolation increases, lipid accumulations appear, and the proportional volume of cytoplasm is reduced accordingly. The findings are integrated into a general hypothesis to explain the genesis and participation of cell components involved directly in hyphal tip growth: Membrane material from the endoplasmic reticulum is transferred to dictyosome cisternae by blebbing; cisternal membranes are transformed from ER‐like to plasma membrane‐like during cisternal maturation; secretory vesicles released from dictyosomes migrate to the hyphal apex, fuse with the plasma membrane, and liberate their contents into the wall region. This allows a plasma membrane increase at the hyphal apex equal to the membrane surface of the incorporated vesicles as well as a contribution of the vesicle contents to surface expansion.
ANOMALOUS SUBSTRATE SPECIFICITIES AMONG THE ALGAL PEROXIDASES
Authors: Siegel B. Z. , Siegel S. M.
Published: January 2018

Semipurified tissue preparations from 13 red and brown algae oxidized pyrogallol and p‐coumaric acid but could not oxidize guaiacol and other ortho (methoxy)‐substituted phenols, including common lignin precursors such as coniferaldehyde. They also failed to oxidize the aromatic amine, benzidine. In contrast, preparations from green algae were like horseradish peroxidase and vascular plant preparations in their ability to oxidize unsubstituted phenols, those substituted at one or both ortho‐positions, and benzidine. One brown alga, Postelsia, was also unable to oxidize the commonplace peroxidase substrates, iodide and eugenol. These results suggest a phylogenetic limitation on the potential for lignification based upon enzyme stereospecificity.
ON A NEW STRUCTURALLY PRESERVED ARBORESCENT LYCOPSID FRUCTIFICATION FROM THE LOWER PENNSYLVANIAN OF NORTH AMERICA
Authors: Brack Sheila D.
Published: January 2018

Bisporangiate lycopsid fructifications are described from petrifaction material of Pottsville (lower Pennsylvanian) age collected in eastern Kentucky. The largest specimen ofLepidostrobus schopfiisp. n. is 8.0 cm long and approximately 1.3 cm in diam; it is not complete at either apex or base. Basal megasporangia, each containing a variable number (12‐29) of megaspores, and apical microsporangia are adaxially positioned on pedicels bearing reduced lateral laminae. Features of the cone axis and pattern of vascularization are described. Of particular interest is the occurrence of well‐preserved endosporic megagametophytes showing archegonia and rhizoids. The new species is compared with other structurally preserved bisporangiate lycopsid fructifications of equivalent age.
A MORPHOGENETIC STUDY OF LEAF ABSCISSION IN PHASEOLUS
Authors: Webster Barbara D.
Published: January 2018

Leaf abscission in Phaseolus vulgaris L., the red kidney bean, is presumed to involve a precisely regulated set of interlocking reactions, all of which are subject to control and many of which are detectable morphologically and histochemically. Four sequential stages which culminate in separation are distinct in the laminar abscission region. These include 1) pith cell breakdown, which may not be related to abscission; 2) cell division; 3) cellular differentiation; and 4) cortical and vascular cell breakdown. Correlation of the time and the nature of these structural changes with the period of effectiveness of certain applied growth regulators provides some interesting insights into the nature of the regulatory mechanisms in abscission. A reevaluation of some contemporary concepts of abscission, particularly the characterization of abscission as a senescence phenomenon, is suggested.
TISSUE CULTURE OF CALLUS FROM SEEDLING AND ADULT STAGES OF HEDERA HELIX
Authors: Robbins William J. , Hervey Annette
Published: January 2018

Callus from stem pieces of the juvenile (seedling) and adult stages of Hedera helix L. were grown for up to 17 passages on a medium containing mineral salts, vitamins, sucrose, and coconut water and for fewer passages on media which lacked coconut water. Seedling callus differed in its growth in culture from adult. It was less stable than the adult; i.e., it developed vigorous variants earlier and more freely than the adult callus. The tendency of seedling callus to adapt to unfavorable media was greater. On low salt media root formation by callus was infrequent. Adult calluses formed roots more freely on high salt media than seedling calluses did.
DEVELOPMENT OF THE PISTILLATE FLOWER IN THE DWARF MISTLETOES, ARCEUTHOBIUM
Authors: Cohen Leon I.
Published: January 2018

The pistillate flowers of Arceuthobium show a high degree of uniformity and structural simplicity. Because of their simplicity certain structures such as the carpel and the placenta have been difficult to interpret. From this study, the placenta is interpreted as a composite structure consisting of two united ovules fused basally with the tissues of the receptacle. Pollen tube penetration of the placenta at its tip, development of the zygote at the distal pole, and early endosperm formation at the basal pole of the former megagametophyte indicate that the ovule is orthotropous. A theoretical interpretation of gynoecial phylogeny in Arceuthobium is discussed.
SHOOT GROWTH AND LEAF DIMORPHISM IN BOSTON IVY (PARTHENOCISSUS TRICUSPIDATA)
Authors: Ckitchfield William B.
Published: January 2018

Boston ivy, a common ornamental vine in the grape family, successively produces two kinds of leaves during the growing season. The two “early leaves” at the base of each shoot are preformed in the winter bud, and their expansion in the spring is accompanied by little stem elongation. At maturity they have large three‐lobed blades and long petioles. Most short shoots produce no more leaves, but “late leaves” develop on all long shoots at intervals of less than 2 days. All but the first few undergo their entire development during the growing season. They are much smaller than early leaves, and the lateral lobes of their blades are reduced or eliminated. They are separated from the early leaves and from each other by long internodes. The early and late leaves differ in the circumstances and continuity of ontogeny, and diverge in form at an early stage. This vine and its relatives are unique in their three‐node cyclical pattern of organ occurrence and internode length along the shoot. Lateral shoots and buds are present at every third node, with tendrils at intervening nodes. The long shoots branch freely and repeatedly, and the production of late leaves and new shoot axes by vigorous compound shoots is limited only by the growing season. Despite its specialized organization, Boston ivy resembles several tree species in its association between a seasonal type of leaf dimorphism and a shoot system constructed of long and short shoots.
PICEA DIETTERTIANA, A NEW SPECIES OF PETRIFIED CONES FROM THE OLIGOCENE OF WESTERN MONTANA
Authors: Miller Charles N.
Published: January 2018

Fossils described in this treatment are the first structurally‐preserved ovulate cones of Picea to be reported from the Tertiary. They are 5.0‐5.8 cm long and 1.6‐1.8 cm at their widest diameter. Numerous ovuliferous scales are arranged spirally around the axis and each bore two winged seeds. The bract subtending the scale is 4.0‐7.0 mm long and is fused to the scale for 1.0 mm. The base of the bract is inflated on the abaxial side extending for about 1.0 mm between the seeds of the adjacent scales. Both the scales and their subtending bracts are recurved at their point of divergence from the axis. The ovuliferous scales taper gradually to a point, and the thickness of the tissues at the scale apex indicates that they were woody. Anatomically, the silicified cones are very similar to those of the Recent species and indicate that all important features of the latter had evolved by Oligocene time.
ULTRASTRUCTURAL STUDIES ON TWO KINDS OF MESOCARYOTIC DINOFLAGELLATE NUCLEI
Authors: Zingmark Richard G.
Published: January 2018

The nucleus of the mesocaryotic dinoflagellate has unusually distinctive features as seen under the light and electron microscope. An electron microscope study of 7 species has demonstrated two kinds of dinoflagellate nuclei. One type, characteristic of Amphidinium and most other dinoflagellates and called here the dinocaryotic type, is distinguished by the presence of discrete chromosomes visible throughout the entire cell cycle. The other type, found in vegetative cells of Noctiluca and called here the nocticaryotic type, is characteristically devoid of evident chromosomes at least during interphase. Questions are raised regarding the distinction between the nucleoplasm, chromosomes, and nucleolus of dinoflagellates. As the Heliozoa and Radiolariahave typically eucaroytic nuclei, they should not be considered as part of the Mesocaryota, as has been previously suggested.
CROWN AND INFLORESCENCE DEVELOPMENT IN THE STRAWBERRY, FRAGARIA ANANASSA
Authors: Jahn Otto L. , Dana Malcolm N.
Published: January 2018

Apices of strawberry plants ('Dunlap,’ ‘Sparkle,’ ‘Catskill,’ and ‘Royal Sovereign') were dissected at intervals between August and November. The structure of the crown and any inflorescence were diagrammed, and records made of crown size and number of leaves. Both the diameter of the crown and the diameter of the bud (enclosed primordia) were correlated with the number of leaves on runner plants. The number of leaf primordia was also correlated with both crown and bud diameters. Growth of the older leaf primordia declined earlier in the fall than did growth of younger primordia. This was evident in lower primordium length ratios as the season progressed. Initiation of an inflorescence was first evident as a raising and enlargement of the apical meristem. Initiation of the primary flower began after the bracts of the inflorescence were evident. Floral initiation is centripetal, the sepals appearing first, followed by petals, stamens, and pistils. The phyllotaxy of the crown continues in the bracts of the main axis of the inflorescence. Branches of the inflorescence usually have two bracts. These were not opposite but were closer together on the side nearest the central axis. This structure was associated with variations in the frequency of flower initiation in the axils on the tertiary and higher order axis. Initiation in the quarternary positions was about eight times more frequent in axillary positions facing the outside of the inflorescence than in those positions oriented toward the center.
EVOLUTION AND ADAPTATION OF INFLORESCENCES IN THE HYDROCHARITACEAE
Authors: Kaul Robert B.
Published: January 2018

Inflorescence evolution in the Hydrocharitaceae has involved modification of a complex sympodial system by condensation, loss of bracts, fusion of pedicels in some cases, adnation of branches to the peduncle in others, and progressive loss of later‐formed flowers resulting in one‐flowered inflorescences in many instances. These changes are associated with the transition from entomophily to more specialized water pollination schemes and from the terrestrial to marine and fresh‐water habitats.
SEQUENCE AND PATTERN OF LATERAL ROOT FORMATION IN FIVE SELECTED SPECIES
Authors: Mallory Thomas E. , Chiang Su‐Hwa , Cutter Elizabeth G. , Gifford E. M.
Published: January 2018

The proximal‐distal distribution of the lateral roots of five species was studied. A detailed investigation was carried out on two of the five species, Ceratopteris thalictroides and Cucurbita maxima. A definite pattern of lateral root arrangement, with a degree of variability related to the number of protoxylem poles, was found in all of the species studied. In the fern Ceratopteris, lateral root initiation was found to be related to the segmentation of the apical cell, which in turn determines the distribution of the laterals. In this species the lateral roots occur in a predictable sequence and they are grouped in pairs. In the angiosperms studied, the pattern of lateral root distribution seemed to depend primarily upon a rather strict longitudinal relationship between the lateral root primordia formed opposite any one protoxylem pole. In Cucurbita maxima, 93.7 ± 5.02% of the lateral root primordia observed were in a specific sequence. The laterals of this species are also arranged in groups. In the other plants studied, Arachis hypogaea, Victoria trickeri, and Eichhornia crassipes, the laterals were not as regularly arranged, but nevertheless they were found to be arranged in groups along the main root axis and not randomly dispersed. Factors controlling the spacing of lateral root primordia include their relationship with the developing vascular system, a direct effect of the parent root apex, and an effect of older lateral root primordia in the same sector of the root.
SEROLOGICAL INVESTIGATION OF THE SYSTEMATIC POSITION OF THE CAPRIFOLIACEAE. I. CORRESPONDENCE WITH SELECTED RUBIACEAE AND CORNACEAE
Authors: Hillebrand Gary R. , Fairbrothers David E.
Published: January 2018

Serological techniques of double diffusion (Ouchterlony) and nephelometry (Boyden Procedure) were employed to analyze the serological correspondence of taxa belonging to the Caprifoliaceae with selected taxa belonging to the Rubiaceae and the Cornaceae. Cornus (Cornaceae) exhibited relatively high correspondence with most representatives of the Caprifoliaceae, especially with Sambucus. The correspondence of Viburnum with Cornus was low. The serological correspondence of genera of the Caprifoliaceae with three genera of the Rubiaceae was relatively low indicating that these two families are serologically distinct. The correspondence between the Caprifoliaceae and the Cornaceae suggests a closer relationship between these two families than between the Caprifoliaceae and the tested genera of the Rubiaceae. These limited data suggest that the Rubiaceae and the Caprifoliaceae should not be placed in one taxonomic order. However, the serological variation for additional taxa within the Rubiaceae must be ascertained before more conclusive statements can be made relative to the degree of serological similarity between the two families.
ENTRY OF BASIC MACROMOLECULES INTO BARLEY ROOTS
Authors: Drew M. C. , Seear Joan , McLaren A. D.
Published: January 2018

The entry of labelled calf‐thymus histone, lysozyme, and poly‐L‐lysine into barley root tips was studied at concentrations which strongly inhibit root elongation. The macromolecules were suitably labelled and at these concentrations it was found, by autoradiography and fluorescence microscopy, that histone and lysozyme readily entered the roots and appeared to bind mainly to cell walls of the epidermis and cortex and to penetrate the cytoplasm occasionally. Except in cap cells, nuclei were rarely penetrated. Poly‐L‐lysine readily permeated cell walls and invaded cytoplasm and nuclei throughout the root tip. Some cells were damaged by contact with basic macromolecules, as evidenced by a change in appearance of protoplasts under phase contrast and by the inability of these same protoplasts to exclude labelled β‐lactoglobulin. Such damage was restricted to cells in contact with the outer solution. Interior to the epidermis, development of many cells was inhibited without visible signs of damage. Evidence supports the conclusion that in the presence of polybasic polymers the integrity of cell membranes is altered, thereby allowing leakage of some cell constituents essential for normal development.
PHYTOCHROME CONTROLLED NYCTINASTY IN ALBIZZIA JULIBRISSIN. II. POTASSIUM FLUX AS A BASIS FOR LEAFLET MOVEMENT
Authors: Satter Ruth L. , Marinoff Philip , Galston Arthur W.
Published: January 2018

Excised Albizzia leaflet pairs exposed to red (R) light close within 30–90 min after transfer to darkness. Interruption of darkness by far‐red (FR) light at any time after R inhibits closure within ca. 10 min. Similarly, irradiation with R at any time after prior FR promotes closure within ca. 10 min, and the increased rate of closure is independent of the time lapse between the FR and R irradiations. Closure in the dark is inhibited by NaN3 and DNP (5 X 10–4 m), by anaerobic conditions and by externally applied salts of monovalent cations, especially K; it is also temperature sensitive. Pulvinule cells are very high in K. Electron microprobe analysis of cryostated, lyophilized pulvinules reveals that during closure, K is lost from ventral cells and enters dorsal cells. FR before darkness inhibits the former but not the latter process. Thus, K flux appears to control the changes in volume of the pulvinule cells that control leaflet movement. While leaflet closure normally requires a dark period, salts of organic acids such as sodium acetate, propionate, and butyrate cause closure in the light.
LATICIFERS IN THE BULB SCALES OF ALLIUM
Authors: Huang Shiu‐mei , Sterling Clarence
Published: January 2018

The structure and distribution of laticifers has been studied in the bulb scales of 52 species and varieties of Allium. Differences in laticifer position, shape, and pitting in the cross wall of the observed specimens support Traub's separation of the subgenera Amerallium and Allium within the genus Allium. If the species examined are representative, anatomical evidence also justifies the distinction of the section Melanocrommyum and the subsection Cepa.
POLLEN FLOW WITHIN A TRISTYLOUS SPECIES: LYTHRUM SALICARIA
Authors: Mulcahy David L. , Caporello David
Published: January 2018

Lythrum salicaria L. is a classic example of tristyly. Pollen flow within a natural population of this species was studied by analyzing pollen loads on stigmas of both intact and emasculated plants. The data obtained indicated that a significant amount of self pollination occurs within flowers but that between flowers or plants pollinations are predominantly legitimate, i.e. between stamens and styles of equal length. It is concluded that while the multiallelic system excels in reducing frequency of incompatible pollinations between plants, the heteromorphic system is relatively more effective in reducing self pollinations within a plant.
STRUCTURE OF TRACHEIDS IN THREE SPECIES OF LYCOPODIUM
Authors: Wilder George J.
Published: January 2018

The structure of tracheids in Lycopodium lucidulum, L. clavatum, and L. tristachyum was studied with the light microscope. Protoxylem development is at least sometimes and possibly always mesarch in indeterminate axes of all three species. Centrifugally formed protoxylem elements are reticulate and discontinuities in the secondary walls of these elements are sometimes conspicuously bordered. Wall thickenings of first formed protoxylem elements consist mainly of indirectly connected rings. Late centripetally formed protoxylem elements and transitional elements have a reticulate secondary wall pattern. The narrowest metaxylem elements have circular bordered pits while in wider metaxylem elements pits are bordered and may vary from circular to scalariform. Pitting is uniseriate to triseriate in tracheids of all three species, and intermittent tetraseriate pitting was occasionally observed in L. lucidulum. Crassulae occur in tracheids of the three species, and in L. clavatum an additional framework, probably representing thickened compound middle lamella, is also present. Pits often appear helically arranged, and in all three species pits are connected by thin areas in the secondary wall. Macrofibrils approximately 0.5 μ wide were observed in tracheids of the three species. In L. clavatum the arrangement of macro‐fibrils was predominantly bidirectional.
CHROMOSOMES OF GRAPTOPETALUM AND THOMPSONELLA (CRASSULACEAE)
Authors: Uhl Charles H.
Published: January 2018

Chromosome numbers are reported for probably all 11 species of Graptopetalum (x = 30–35) and for both species of Thompsonella (x = 26). Plants of two species of Graptopetalum have gametic numbers from about 240–275, more than have been reported in any other seed plants. In hybrids the 30–35 chromosomes in the basic genome of Graptopetalum and likewise the 26 in Thompsonella apparently do not pair among themselves, and the genomes seem to be no more potent genetically than those of other species in their subfamily having as few as 12 chromosomes. Species with these gametic numbers are therefore considered to be diploid. On the other hand, in hybrids between a diploid and a plant with a very high chromosome number the phenotype of the latter predominates, and most of its chromosomes pair with each other. Many such hybrids are fertile. These facts suggest that the high polyploids arose by autoploidy rather than by alloploidy. Nevertheless, they may store heterozygosity at some gene loci and release it in various dosages and proportions each generation.
POPULATIONAL AND GENETIC STUDIES OF A HOMOSPOROUS FERN—OSMUNDA REGALIS
Authors: Klekowski Edward J.
Published: January 2018

The mating system and the genetic system of the homosporous fern Osmunda regalis were investigated. Seven populations from western Massachusetts were sampled. All the sporophytes investigated were found to be heterozygous for zygotic lethals. Morphological studies of the gametophytes indicated an intergametophytic mating system when the gametophytes were spatially and chronologically situated to exchange male gametes. Genetic studies evidenced a genetic system based upon duplicate loci.
SPONTANEOUS AND INDUCED CHROMOSOME BREAKAGE IN CLAYTONIA VIRGINICA
Authors: Star Aura E.
Published: January 2018

Meiocytes in three morphologically similar but cytologically different wild populations of Claytonia virginica L. were examined. Over a three‐year period levels of spontaneous chromosome breakage were consistent for each population but differed between populations. Random samples of inflorescences from two of the populations were treated with 0.005 % aqueous solutions of nucleic acid precursors: adenine, adenosine, thymine, thymidine, guanosine 5'‐monophosphate (GMP), and cytosine 5'‐monophosphate (CMP). Statistically significant increases in chromosome breakage were observed in the population with little background breakage when inflorescences were treated with adenosine, thymine, thymidine, GMP, and CMP. In the population with moderate spontaneous breakage, a significant increase was observed only in plants treated with adenosine. Breakage induced with nucleic acid precursors was similar to that which occurred spontaneously; the predominant aberration was the single bridge.
ORIGIN AND DEVELOPMENT OF THE TERMINAL CARPEL IN PSEUDOWINTERA TRAVERSII
Authors: Sampson F. B. , Kaplan Donald R.
Published: January 2018

Flowers of Pseudowintera traversii (Buchan.) Dandy possess a terminal unicarpellate gynoecium. The present study of carpel morphogenesis was initiated for the purposes of (1) providing additional developmental documentation of the occurrence of terminal carpels in the Winteraceae and (2) comparing the mode of initiation and development of the ascidiate terminal carpel of P. traversii with the essentially conduplicate terminal carpel of Drimys lanceolata. Following its axillary origin, the floral apex of P. traversii initiates 2–3 connate sepals, 5–6 petals, 4–15 stamens, and usually a single terminal carpel, in acropetal succession. Bicarpellate gynoecia may occur with a frequency of up to 15 % on a given plant. The floral apex is zonate and shows increased expression of its zonation during later stages of floral development. The terminal carpel is ascidiate from inception and originates as a cylindrical growth around the entire circumference of the floral apex; transformation of the floral meristem into a carpel primordium terminates apical growth of the floral axis. Carpel growth continues to be cylindrical and is mediated by a ring of marginal and submarginal initials at its summit. Earlier and more extensive division of initials and their derivatives on the dorsal rim causes the primordium to become canted adaxially, shifting the apical cleft to a subterminal adaxial position. Continued marginal meristematic activity results in closure of the cleft as well as elevation and elaboration of the stigmatic crests. Five to seven bitegmic ovules are initiated at the same time as crest elaboration and arise in two rows from the adaxial (laminar) position. Carpel maturation is signified by tannin deposition and oil cell differentiation, beginning at the base and proceeding acropetally; carpel margins bordering the cleft are the last to differentiate. Carpel procambialization is continuous and acropetal from inception, with the dorsal median bundle differentiating before the ventral strands. The significance of occasional bicarpellate flowers is discussed.
SYNCOTYLY IN QUERCUS ARIZONICA
Authors: Mogensen H. Lloyd
Published: January 2018

An investigation was made concerning the gross morphology and the internal anatomy of Quercus arizonica embryos. It was found that the percentage of fused‐ and separate‐cotyledoned embryos varies from tree to tree. Fusion of the cotyledons is congenital. Intermediate stages of fusion occur. The vascular pattern is the same in both fused‐ and separate‐cotyledoned embryos. The number of cotyledonary traces varies in both types of embryos. The relationship of the single‐cotyledoned embryo of Quercus to the origin of monocotyly is discussed.
THE EFFECT OF SUGARS AND APPLIED CHEMICALS ON HETEROBLASTIC DEVELOPMENT IN IPOMOEA PURPUREA GROWN IN ASEPTIC CULTURE
Authors: Njoku Eni
Published: January 2018

Seedlings of Ipomoea purpurea were grown in aseptic culture in order to investigate more directly than had been possible in pot culture the effect of carbohydrate and protein nutrition on heteroblastic development which in this species involves a change from entire juvenile to lobed adult leaves. The effect of sugars was to accelerate the development of the adult leaf form while casein hydrolysate retarded it. The growth retardants, AMO‐1618 and CCC, also promoted the formation of the adult leaf. These results are discussed in the light of current views on the factors controlling heteroblastic development.
HISTOCHEMISTRY OF THE RHIZOMORPH MERISTEM OF ARMILLARIA MELLEA
Authors: Motta Jerome J.
Published: January 2018

Histochemical studies disclose the presence of relatively large amounts of protein and nucleic acids in the apical region of the rhizomorph of Armillaria mellea. No specific center for the production of protein was noted, but nucleic acid studies suggest that RNA synthesis may be confined to a limited region of the rhizomorph tip. Intranuclear, crystalline protein bodies are present while selective fluorescent staining of DNA indicates that the relative amounts of that substance, per nucleus, may be quite small and may account for some of the difficulty in selective nuclear staining by more commonly employed methods. Large stores of glycogen in the area adjacent to the apical center and its apparent rapid turnover in that region implicates this polysaccharide as a participant in the differentiation of the primary medulla.
VARIATIONS IN POLYMNIA POLLEN
Authors: Wells James R.
Published: January 2018

Photomicrographs of normal and aberrant Polymnia (Compositae) pollen were made with the scanning electron microscope and with the light microscope. Anomalous pollen forms from F1 hybrids of P. maculata Cav. are compared to the parental type and to the closely related P. uvedalia (L.) L. Among the variations discussed are differences in size and form, fused aggregates, and reduction in length of spines. The cause of these variations is unknown, although similar anomalies were later found in a single P. maculata parent, Wells No. 740, which grew under similar standard greenhouse conditions.
THE EFFECTS OF AMINO ACIDS UPON THE DEVELOPMENT OF EXCISED FLORAL BUDS OF AQUILEGIA
Authors: Bilderback David E.
Published: January 2018

Young excised floral buds of Aquilegia were grown on a chemically defined medium containing various concentrations of single amino acids or mixtures of amino acids. γ‐Amino butyric acid significantly promoted floral development through the initiation and differentiation of carpels. These floral organs were generally absent on the basal medium. Alanine, glutamic acid, and aspartic acid had no effect upon floral development. All other amino acids were either ineffective at lower concentrations and inhibitory at higher concentrations or were inhibitory at all concentrations. Casein hydrolysate and a mixture of amino acids found in coconut milk were ineffective. The addition of both γ‐amino butyric acid and alanine to the basal medium promoted development approaching that achieved on the coconut‐milk medium. However, further growth factors appear to be required before development on coconut‐milk medium is equalled or exceeded.
LYSSOXYLON GRIGSBYI, A CYCAD TRUNK FROM THE UPPER TRIASSIC OF ARIZONA AND NEW MEXICO
Authors: Gould R. E.
Published: January 2018

Lyssoxylon grigsbyi Daugherty, a petrified stem with petiole bases, was originally described from the Upper Triassic Chinle Formation of Arizona and considered to be a member of the Williamsoniaceae. Investigation of additional material from a similar horizon in New Mexico, together with re‐examination of preparations of the holotype, suggest that the plant, with its monoxylic stele, girdling leaf traces, and bicelled epidermal hairs is a true cycad. Cells of the New Mexico specimens contain structures interpreted as preserved nuclei.
SELECTIVITY MECHANISM FOR THE DIFFERENTIAL DESTRUCTION OF PLANT TISSUES BY METHYL DECANOATE EMULSION
Authors: Nelson Paul V. , Reid Robert K.
Published: January 2018

Methyl decanoate emulsified with Tween 20 and sprayed on chrysanthemum plants kills the immature tissues. The mechanism of selectivity was found to be a property of the cuticle which acts as a penetration barrier to the emulsion. Disruption of cuticles before emulsion application resulted in death of underlying cells due to membrane destruction, as shown by electron microscopy. Small quantities of methyl decanoate, however, do penetrate the unaltered cuticle, resulting in moderate, reversible alterations to the ultrastructure of the cell. These alterations appear as aggregates of vesicles in the cytoplasm and larger aggregates of vesicles in the vacuole. No destruction of organelle membranes occurred, and visual symptoms were not seen. The marginal cuticular penetration was verified by isolated cuticle tests.
LIGHT AND SCANNING ELECTRON MICROSCOPIC STUDIES ON POLLEN OF TETRAPLASANDRA (ARALIACEAE) AND RELATIVES
Authors: Tseng Charles C.
Published: January 2018

Pollen of seven species inTetraplasandraand three species in related genera were studied with light and scanning electron microscopes. A new thin‐section technique was employed for the study of exine stratification and apertural structure. This study reveals several previously undescribed pollen structures for the group. Trends toward increase in pollen size and in specialization of other pollen characters are evident inTetraplasandra. Pollen ofReynoldsiaandPeekeliopanaxdiffers fromTetraplasandrain the pertectate sexine and the absence of inner nexinous breaks, respectively. A pollen correlation study shows thatMunroidendronfalls readily within the genusTetraplasandrabut is distinguishable from the latter by its bifurcate colpi.
CYANOPHYTE CEPHALODIA IN THE LICHEN GENUS NEPHROMA
Authors: Jordan William Paul , Rickson Fred R.
Published: January 2018

The lichens, Nephroma expallidum (Nyl.) Nyl. and N. arcticum (L.) Torss., consistently have at least two symbionts in a single thallus: a green alga in the algal layer and a blue‐green alga in the internal cephalodia. The cephalodia originate from algal cells in contact with the lower surface of the lichen, in the zone of rhizine formation. The rhizines surround the epiphytic algal colony and form a second cortical layer; following dissociation of the original lower cortex, further growth of the two organisms results in the cyanophyte colony being enveloped by a compact layer of fungal tissue and positioned in the lichen medulla. The colony may eventually assume a superior or inferior position in relation to the lichen thallus, depending in part on the lichen species. Nephroma anticum may have two distinct morphological forms of blue‐green algae in the same thallus and occasionally in the same cephalodium. It appears that the relationship that exists between the cephalodial algae and the lichen thallus is antagonistic and results, in some cases, in the exclusion of the green algal layer and death to the cephalodial cyanophytes.
ANATOMY OF A LIGNITIZED WOOD FROM SENFTENBERG
Authors: Morey Philip R. , Morey Elsie D.
Published: January 2018

A piece of lignitized wood from the Miocene of Senftenberg, Germany, was identified as a type of compression wood, and was studied anatomically, as groundwork, in an investigation on cell wall cellulose and lignin. The wood showed affinity to modern Cryptomeria and Taxodium. In each growth ring the early wood was compacted. By contrast, cellular structure in the late wood had been retained to a high degree. Massive compaction of the early wood most likely occurred during the initial stages of sedimentation prior to mineralization. Numerous cell wall deformations in late wood tracheids apparently originated from compressive forces applied to the wood during sedimentation.
MORPHOLOGY AND ANATOMY OF NEW SPECIES OF SCHIZAEA AND ACTINOSTACHYS
Authors: Bierhorst David W.
Published: January 2018

The gametophyte, old embryo, and sporophyte of Schizaea pseudodichotoma sp. nov., sporophyte and female parental gametophyte of S. diversispora hybr. nov. (S. pseudodicholoma X probably S. dichotoma), sporophyte of S. rhacoindusiata sp. nov., and gametophyte, old embryo, and sporophyte of Actinostachys macrofunda sp. nov. are described. The taxonomy of Schizaea is discussed and the system of Diels is strongly supported. The two sectional names used by Diels, Euschizaea Hook, and Lophidium Rich, are replaced by Pectinatae Prantl and Schizaea respectively. The prime morphological significance of Schizaea pseudodicholoma lies in its leafless embryo and its simple leaf differing from other species in its section, and that of Actinostachys macrofunda lies in its reduction to nearly complete heterotrophic existence and its frequent multiple annulus. Fungal hyphae have been traced from Schizaea and Actinostachys through the substratum and into root nodules of Casuarina and into roots of two other angiosperms.
A PERIODIC ACID‐SCHIFF'S SUBSTANCE RELATED TO THE DIRECTIONAL GROWTH OF POLLEN TUBE INTO EMBRYO SAC IN PASPALUM OVULES
Authors: Chao Chuan‐ying
Published: January 2018

The presence of a periodic acid‐Schiff's (PAS) substance at the micropylar portion of the ovules of Paspalum orbiculare and three other species of Paspalum has been revealed by improved cytological techniques. The substance is located in the distal portion of the outer integument, especially at its edges, and in the micropyle, which is formed by the inner integument. A study of the origin of this substance in P. orbiculare indicates that it is produced from the cellular material of the dissolved cells in situ. The PAS substance is highly water soluble and may contain some protein. The final directional growth of the pollen tube into the filiform apparatus of the degenerated synergid is related to this substance. The role of the synergids in its formation is discussed.
THE QUIESCENT CENTER IN CULTURED ROOTS OF CONVOLVULUS ARVENSIS L.
Authors: Phillips Harry L. , Torrey John G.
Published: January 2018

Cultured roots of Convolvulus arvensis were incubated in 0.2–0.3 μc/ml methyl‐3H‐thymidine for different intervals of time. In roots supplied with tritiated thymidine for 12 hr, 14 hr, 48 hr, or 14 hr followed by transfer to fresh medium for 24 hr, autoradiographs prepared of serial, longitudinal sections of the root tips showed the presence of a subterminal quiescent center in the root proper at the distal poles of the central cylinder and cortex. In addition, a zone of unlabelled cells in the columella, distal to the root cap initials, was present. In roots supplied continuously with tritiated thymidine for 64 hr, 96 hr, and 120 hr, the quiescent center was either reduced in size or was not present.
THE EFFECT OF VARIOUS FIXATION SCHEDULES ON THE SCANNING ELECTRON MICROSCOPIC IMAGE OF TROPAEOLUM MAJUS
Authors: Falk Richard H. , Gifford E. M. , Cutter E. G.
Published: January 2018

Fresh, unfixed shoot tips of Tropaeolum provided excellent quality scanning electron micrographs if observations were brief and magnifications were relatively low. For extended observations or for high‐magnification observations, fixation by OsO4 vapor or Zirkle‐Erliki's fluid provided the best scanning electron micrographs. Brief exposures to microscope vacuum do not appear to produce any apparent morphological changes in living shoot tips of Tropaeolum except in regions adjacent to a cut surface.
CHROMOSOME NUMBERS AND PHYLOGENY IN MELAMPODIUM (COMPOSITAE)
Authors: Stuessy Tod F.
Published: January 2018

The haplord chromosome numbers of n = 9, 10, 11, 12, 18, 20, 23, 25 ± 1, 27, 30, and 33 have been reported by various authors from 26 of the 37 recognized species of Melampodium. A chromosomal survey of 375 plants from 275 different populations suggests that the recorded numbers are stable within the genus and that infraspecific euploidy and aneuploidy are uncommon. These chromosome numbers can be arranged numerically, with morphological and limited cytogenetic substantiation, into four euploid series of x2 = 9, 10, 11, and 12. Of these four groups of species, the x = 10 series is the largest and morphologically most diverse. This consideration, along with additional evidence from the morphology of sterile disc ovaries, suggests that x = 10 is the ancestral chromosomal base in Melampodium. A comparison of morphological and cytological data from the closely related genera, Acanthospermum and Lecocarpus, indicates that the latter are probably on a common base of x = 11. Present day distributional patterns of all three genera support the hypothesis that x = 10 is the ancestral base for the entire complex.
HYBRIDIZATION AND CYTOTAXONOMY OF DICENTRA
Authors: Stern Kingsley R. , Ownbey Marion
Published: January 2018

Biosystematic relationships among species assigned to three subgenera of the genus Dicentra were investigated with respect to hybridization and chromosomal constitution and fertility of the hybrids. Four species of subgenus Dicentra, D. formosa, D. eximia, D. nevadensis, and D. peregrina, were intercrossed in various ways to form diploid, triploid, and tetraploid hybrids. Hybrids at the tetraploid level in this subgenus invariably were highly fertile. Triploid hybrids, as expected, were mostly very sterile. Diploid hybrids varied in this respect, but none was highly fertile. Crosses with two of the remaining four species of subgenus Dicentra produced no hybrids, but abundant seed was obtained in one instance. The two species of the subgenus Chrysocapnos, D. chrysaniha and D. ochroleuca, cross to produce a partially fertile tetraploid hybrid, but cross‐pollinations involving these species with those of other subgenera failed. The single species of subgenus Hedycapnos, D. spectablis (diploid) produced no hybrids when cross‐pollinated with members of the other two sections. These results are fully concordant with presumed affinities based on morphological similarity In addition, preliminary results of hybridization between the monocotyledonous D. peregrina and a number of dicotyledonous species of Dicentra are reported.