bluuebunny/crossref_metadata_2025 huggingface dataset:
POLYRIBOSOMES IN PROLIFERATING AND NONPROLIFERATING ROOT MERISTEM CELLS
Authors: Webster Peter L. , Hof Jack Van't
Published: January 2018

Pea root meristem cells which are actively dividing contain higher proportions of polyribosomes than do cells whose progression through the mitotic cycle has been arrested by starvation. The initiation of cell division which follows the addition of sucrose to starved roots is accompanied by an increase in polyribosome content. This reformation of polyribosomes is insensitive to actinomycin D; it is suggested that preexisting mRNA molecules, synthesized prior to starvation, participate in polyribosome reformation, but that those mRNA species necessary for movement of cells through the mitotic cycle are gradually lost during the starvation period.
PENETRATION OF 2,4‐D IN RELATION TO CUTICLE THICKNESS
Authors: Norris Robert F.
Published: January 2018

Cuticle thickness was measured, either by direct microscopic examination or as weight per unit area, for the astomatous cuticle from the upper leaf surface of nine species and from tomato fruit. Thickness ranged from 1.4 μm for peach leaf cuticle to 10.8 μm for oleander leaf cuticle, and the weight from 0.19 mg/cm2 to 1.26 mg/cm2, respectively. Cuticles were isolated by the pectinase method and permeability to 2,4‐D was determined. There was no correlation between cuticle thickness and penetration of 2,4‐D, either for non‐dewaxed cuticles or after chloroform extraction of waxes. Penetration of 2,4‐D was increased following wax removal, but there was no correlation between wax content and the magnitude of the increase. It is suggested that cutin and wax qualitative composition are probably more important than thickness in determining relative permeability of cuticle from different plant species to 2,4‐D.
THE VASCULAR TRANSITION REGION OF HELIANTHUS ANNUUS (COMPOSITAE). II. EFFECT OF IONIZING RADIATION
Authors: Scheirer Daniel C. , Hillson Charles J.
Published: January 2018

The vascular pattern in the transition region of Helianthus annuus L. may be altered by ionizing radiation in dosages ranging from 650–19,200 R. The alteration of the vascular cylinder is expressed by (1) the failure of normal tracheary elements to mature and (2) by the induction of accessory xylem and/or phloem strands. The anatomical alterations in the vasculature of the transition region are presented and their significance discussed in terms of seedling survival and the mechanisms controlling vascular differentiation.
NUTRITIONAL AND MORPHOGENETIC INVESTIGATIONS ON CALLUS CULTURES OF NEOMAMMILLARIA PROFILERA MILLER (CACTACEAE)
Authors: Minocha Subhash C. , Mehra P. N.
Published: January 2018

Neomammillaria prolifera (Cactaceae), when grown on Murashige and Skoog's medium supplemented with fresh coconut milk, showed very little growth. Various concentrations and combinations of growth regulators which did not cause callusing had no apparent effect on the normal growth rates of intact plants. Healthy green calli obtained on a 2,4‐D and kinetin‐containing medium exhibited extremely fast growth and very specific growth requirements. Relatively high amounts of 2,4‐D (10–20 mg/liter), kinetin (1–2 mg/liter), and coconut milk (20–60%) were required at all times for continued proliferation of callus on subculturing. Moreover, the callus was very tolerant to extremely high concentrations of other growth regulators (IAA, NAA, IBA, and GA up to 100 mg/liter) in the presence of 2,4‐D and coconut milk. These substances could not replace 2,4‐D for callusing or continued growth of callus. It was not possible to establish root cultures or to induce callusing of roots. Attempts to induce differentiation in callus were unsuccessful, except for sporadic root initiation in some cultures. A comparison of these results with similar studies on other succulents demonstrates some basic physiological similarities among this group of plants.
TWO NEW MEMBERS OF THE BLASTOCLADIACEAE. I. TAXONOMY, WITH AN EVALUATION OF GENERA AND INTERRELATIONSHIPS IN THE FAMILY
Authors: Emerson Ralph , Robertson Jack A.
Published: January 2018

Two new fungi in a small family of zoosporic phycomycetes, the Blastocladiaceae, are described. Both are included in the Brachyallomyces category, as sexuality has not been found in either one thus far. Microallomyces dendroideus from Costa Rica represents a new genus distinguished by its occurrence on animal or plant substrata rich in protein, its branched thallus in which pseudosepta are entirely lacking but growth is renewed by sympodially formed hyphal tips, and its small size. Allomyces reticulatus from California is the first species in this well‐known genus to exhibit reticulately sculptured resistant sporangia. Its robust thallus is also unusual in that, despite the presence of the characteristic pseudosepta and branching with sympodially renewed hyphal tips, growth is ordinarily not unlimited as it is in all other species of the genus. The addition of these two new water molds to the Blastocladiaceae poses some basic questions regarding generic distinctions in the family. These problems are discussed and a working key to the genera is provided.
THE SPORANGIUM OF HORNEOPHYTON LIGNIERI (RHYNIOPHYTINA)
Authors: Eggert Donald A.
Published: January 2018

Numerous sporangia of Horneophyton lignieri from the Rhynie Chert locality in Scotland have been studied. The sporangia are branched, with two to four columellate lobes of varying length, and a continuous sporogenous zone or cavity occurs among the lobes. Unbranched sporangia, generally thought to be the typical form for the plant have not been found, and their presence is not established. Although not definitely proven, evidence suggests that the sporangia opened by means of a small apical pore or stoma. An area of thick‐walled cells at the apex of each sporangial lobe probably played some role in this opening. Radial, trilete, azonate spores ranging from 39–49 μm in diam, with curvaturae perfectae are produced most commonly in tetrahedral tetrads and occasionally in isobilateral tetrads. Matters of spore preservation and possible ornamentation are discussed. The branched sporangia of this genus are unique among bryophytes and vascular plants and provide some evidence that certain synangia may have arisen from a single sporangium rather than from multiple sporangia borne singly at the tips of ultimate branches.
MORPHOLOGICAL AND CYTOLOGICAL VARIABILITY IN TRIPSACUM DACTYLOIDES (GRAMINEAE)
Authors: Newell C. A. , de Wet J. M. J.
Published: January 2018

A total of 235 accessions of Tripsacum dactyloides (L.) L. representing natural populations from 88 locations distributed throughout ten states of the United States were collected in the wild and studied morphologically and cytologically. Multivariate analysis of variance (MANOVA) was applied to 17 morphological characters recorded for 868 specimens from the 88 locations, which were further combined into 25 groups to facilitate analysis. Multivariate F ratios for six comparisons involving different groups were highly significant, indicating that the populations were significantly different on the basis of all 17 characters. Non‐significant MANOVA F ratios for two comparisons between sympatric diploid and polyploid accessions showed them to be morphologically similar. Discriminant function (DF) analysis was employed to determine which characters contributed towards group discrimination. No one variable was found to distinguish between groups; rather, a combination of characters was necessary, and the combination changed with each comparison. Accessions were mainly either diploid (2n = 36) or tetraploid (2n = 72), with two triploids (2n = 54) reported from separate locations in Texas. Cytological data revealed that diploids and tetraploids occupy a more sympatric distribution than previously supposed. Morphological analysis suggested that diploids could not always be distinguished from polyploids on the basis of morphology alone, unless the appropriate characters were used. Information from cytological and morphological data showed Tripsacum dactyloides to be composed of many populations covering a wide range of variability, with each population possessing a characteristic combination of morphological attributes. It was concluded that T. dactyloides can be most meaningfully analyzed in terms of particular geographic regions, rather than attempting to elucidate natural relationships by correlating data from the entire United States.
PROBABLE ATTACHMENT OF THE DOLEROTHECA CAMPANULUM TO A MYELOXYLON‐ALETHOPTERIS TYPE FROND
Authors: Ramanujam C. G. K. , Rothwell Gar W. , Stewart Wilson N.
Published: January 2018

The discovery of pedunculate specimens of pollen organ Dolerotheca in close association with Myeloxylon‐type pinnae and Alethopteris‐type pinnules provides evidence for the reconstruction of a petrified medullosan frond and the attachment of the microsporangiate fructification. Specimens of Dolerotheca villosa and D. formosa from Middle and Upper Pennsylvanian age strata of North America are borne on slender peduncles with anatomical features and vascularization identical to those of some level in a Myeloxylon‐Alethopteris‐type frond. Reconstruction of the frond reveals a large, repeatedly dichotomising organ that bears penultimate pinnae and ultimate pinnules in a pinnate arrangement. Examination of pinnules on the surface of coal ball material indicates that they conform to the compression genus Alethopteris. Identical numbers and arrangement of vascular bundles together with identical anatomical features and multicellular hairs indicate that the Dolerotheca campanulum is borne in the position of a penultimate pinna. A reconstruction of the frond with a proposed polled organ attachment is included.
LEAF DEVELOPMENT IN DOXANTHA UNGUIS‐CATI (BIGNONIACEAE)
Authors: Sistrunk Dan R. , Tucker S. C.
Published: January 2018

Leaf structure in Doxantha unguis‐cati is polymorphic. The usual mature compound leaf is composed of two lanceolate leaflets and a terminal tripartite spine‐tendril. Leaf primordia are initiated simultaneously in pairs on opposite flanks of the shoot apical meristem by periclinal cell divisions in the third subsurface layer of the peripheral flank meristem. Two leaflet primordia are the first lateral appendages of the compound leaf. Initiation of these leaflet primordia occurs on the adaxial side of a compound leaf primordium 63–70 μm long. Lamina formation is initiated at the base of a leaflet primordium 70–90 μm long and continues acropetally. Mesophyll differentiation occurs in later stages of development of leaflets. The second pair of lateral appendages of the leaf primordium differentiate as prongs of the tendril. Initiation of the second pair of lateral appendages occurs on the adaxial side of a primordium approximately 168 μm long. Acropetal procambialization and vacuolation of cells extend to the apex of tendrils about 112 μm long, restricting the tendril meristem to the adaxial side of the primordium and resulting in curvature of the tendril. The tendril meristem is gradually limited to a more basipetal position as elongation of apical cells continues. Initiatory divisions and early ontogenetic stages of leaflets and tendrils are similar. Their ontogeny differs when the lateral primordia are approximately 70 μm long. Marginal and submarginal initials differentiate within leaflets but not in tendrils. Apical growth of tendrils ceases very early in ontogeny as compared with leaflets.
CHLOROPLASTS OF MONOPLOID AND DIPLOID OENOTHERA HOOKERI
Authors: Lee Lily P. , Hecht Adolph
Published: January 2018

Comparison of leaves from diploid Oenothera hookeri plants with leaves of their monoploid derivatives revealed the following differences: the leaves of the diploids are almost twice as thick as those of the monoploids; the diploids have only one‐fifth as many cells per unit leaf area as do the monoploids; leaf tissue of the diploids has an average of 36.3 chloroplasts per cell compared with 27.4 for the monoploids; chloroplasts of the diploids average 4.68 μm in length, those of the monoploids, 3.74 μm; chloroplasts from the diploids contain about seven times more chlorophyll than those of the monoploids and have an average of seven thylakoids per granum compared with an average of only three for the monoploids; the average chlorophyll a/b ratio for the diploid chloroplasts is 2.98 compared with 3.48 for the monoploids.
THE APOGAMOUS LIFE CYCLE OF TRICHOMANES PINNATUM—A CONFIRMATION OF KLEKOWSKI'S PREDICTIONS ON HOMOEOLOGOUS PAIRING
Authors: Bierhorst David W.
Published: January 2018

The gametophyte of Trichomanes pinnatum is filamentous save for its club‐shaped archegoniophores. Gametangial structure is consistent with that of related species. The apogamous embryo originates from the archegonial jacket and contiguous tissue such that there is no external indication of apogamy. The life cycle follows the Döpp‐Manton scheme. Specimens were studied which were homozygous for a paracentric inversion and these showed chromosomal bridges and associated fragments at meiosis‐I, thus confirming cytologically the occurrence of homoeologous pairing.
SOIL‐PLANT PHYTOTOXICITY AND ITS POSSIBLE SIGNIFICANCE IN PATTERNING OF HERBACEOUS VEGETATION IN A BOTTOMLAND FOREST
Authors: Lodhi M. A. K.
Published: January 2018

Plant growth inhibitors, which are known to exert synergistic effects on herbaceous vegetation, were isolated and quantified from the soils under hackberry trees. Ferulic, caffeic, and p‐coumaric acids were isolated from the soils under hackberry trees collected in January, April, and September from 0–15 and 15–30 cm soil depths. Seed germination bioassay indicated considerably higher phytotoxicity levels of individual plant growth inhibitors in January and April soils, and this toxicity level was more drastic when inhibitors were applied accumulatively. Individual phytotoxins extracted from soil in September were not very inhibitory to seed germination of selected test species; however, accumulative effects were still allelopathic to seed germination. Toxicity levels of individual compounds may reduce or disappear in a given time, but the combined action of these chemicals would still be toxic in croplands or in natural communities. Ecological implications of allelopathy in terms of soil‐plant interaction are discussed.
INVESTIGATIONS OF ANGIOSPERMS FROM THE EOCENE OF NORTH AMERICA: A CATKIN WITH JUGLANDACEOUS AFFINITIES
Authors: Crepet W. L. , Dilcher D. L. , Potter F. W.
Published: January 2018

Three specimens of one type of fossil catkin from the Middle Eocene of Tennessee are excellently preserved and have been investigated morphologically. The flowers on these catkins are subtended by elongate, three‐lobed bracts, are exclusively staminate, and have three conspicuous, obovate, perianth parts that bear large peltate scales. The stamens are well preserved and contain triporate pollen grains that are equivalent to the dispersed pollen genus Momipites. Floral morphology, cuticular features, and pollen indicate close affinities with the extant genera Engelhardia, Oreomunnea, and Alfaroa of the Juglandaceae; but because the fossil catkins are distinct and are a dispersed plant organ, they are placed in a new form genus: Eokachyra. These fossil flowers represent a rare opportunity to correlate the micro‐ and macrofossil record and to compare the relative rates of evolution of these features. The fossil catkins also demonstrate that much structural information may be gained from the study of fossil angiosperm flowers. The similarities between the staminate flowers of the fossil catkins and the staminate flowers of Engelhardia, Oreomunnea, and Alfaroa confirm the idea that this complex has had a long evolutionary history and suggest that the pollination system of certain extant genera was well developed during Middle Eocene times.
STUDIES ON SARGASSUM. I. A LIGHT MICROSCOPIC EXAMINATION OF THE WOUND REGENERATION PROCESS IN MATURE STIPES OF S. FILIPENDULA
Authors: Fagerberg Wayne R. , Dawes Clinton J.
Published: January 2018

Regrowth from wounded stipe explants of Sargassum can be divided into four stages based on cytological changes. The first stage involves changes associated with the wound reactions and the formation of a wound epidermis. The second stage includes the formation of a well defined medullary pit with meristematically active cells around its periphery. Several “bud primordia” are also formed which begin to grow by cell division towards the wound surface. The third stage involves a period of internal tissue differentiation in the “bud primordia” such that mitotic activity is localized in the bud tip and the basal cells grow by cell elongation. The fourth stage marks a major change in the morphology of the regeneration branch from a tubular structure to that of a flattened blade. This change in morphology is preceded by the formation of an apical pit around which the flattened growth appears to be organized.
CYTOGEOGRAPHIC EVIDENCE FOR THE EVOLUTION OF DISTYLY FROM TRISTYLY IN THE NORTH AMERICAN SPECIES OF OXALIS SECTION IONOXALIS
Authors: Weller Stephen G. , Denton Melinda F.
Published: January 2018

A survey of haploid chromosome numbers of 18 North American taxa of Oxalis section Ionoxalis was initiated to determine the relationship between ploidal level, geographic distribution, and the occurrence of tristyly and distyly. Although chromosome numbers in the section are variable, the majority of tristylous populations are diploid. Among the distylous taxa a greater diversity of ploidal levels exists, with the higher chromosome numbers predominating. In section Ionoxalis the majority of the tristylous taxa are geographically restricted endemics of southern Mexico, while the distylous taxa have more extensive distributions ranging to the north. The association of diploidy and geographic endemism in the majority of the tristylous taxa suggests that these species are relictual. A few widespread tristylous taxa are polyploid, and often somewhat weedy. The probable derivation of widespread polyploid species from the restricted diploid endemics of southern Mexico appears to have been accompanied by the evolution of distyly from tristyly. The frequent association of polyploidy and distyly in section Ionoxalis has apparently resulted from the concurrence of two evolutionary trends: increase in ploidal level and the derivation of distyly from tristyly.
POST‐POLLINATION PHENOMENA IN ORCHID FLOWERS. VI. EXCISED FLORAL SEGMENTS OF CYMBIDIUM
Authors: Arditti Joseph , Flick Brigitta H.
Published: January 2018

Whole Cymbidium Sw. (Orchidaceae) flowers, ones with their labella, gynostemia or perianth removed as well as excised ovaries, lips and columns, were pollinated, emasculated and treated with NAA and maintained in media containing or lacking NAA. The results indicate that, 1) the rostellar‐stigmatic region seems to control many post‐pollination phenomena, 2) auxin from the medium apparently does not reach the rostellum and/or stigma, 3) there is a certain interdependence among floral segments which exhibit post‐pollination phenomena, and 4) once initiated, these phenomena may be subject to localized effects. These findings are taken as an indication that pollinated orchid flowers are a well‐integrated system despite the diversity and number of observable phenomena.
EVOLUTION IN THE GENUS RUELLIA (ACANTHACEAE): A DISCUSSION BASED ON FLORAL FLAVONOIDS
Authors: Bloom Miriam
Published: January 2018

A clear dichotomy exists in the genus Ruellia, separating the blue from the red flowered species. Flavonoids differ in a qualitative rather than a quantitative way. Apigenin 7‐glucuronide and malvidin 3,5‐diglucoside are common to all the blue flowered species, whereas chalcononaringenin 2'‐glucoside (isosalipurposide) and pelargonidin 3,5‐diglucoside are shared by the red flowered ones.

The blue flowered species are linked with the red via apigenin 7‐glucuronide and 3,5‐diglucosylation of their respective anthocyanins. Both groups are involved in flavonoid race formation. All examined species (and some populations within species) differ in flavonoid content. The patterns of variability displayed provide a basis upon which an evolutionary scheme is constructed. Genetic drift is hypothesized as the effector of race formation in the blue flowered group.
THE CYTOHISTOLOGICAL AND CYTOHISTOCHEMICAL ZONATION OF THE SHOOT APEX OF BOTRYCHIUM MULTIFIDUM
Authors: Stevenson Dennis Wm.
Published: January 2018

Cytohistologically, the shoot apex of Botrychium multifidum is composed of three zones—a zone of surface initials in which there is usually a centrally located apical cell, a zone of subsurface initials, and a cup‐shaped zone that is subdivided into a pheripheral zone and a rib meristem. The results of cytohistochemical tests for total protein, RNA, total carbohydrate, histones, and DNA localization support this concept. Thus, the cytohistological zonation of the apical meristem of the Ophioglossales is essentially identical to that of the Filicales, and furthermore, is comparable to that of the seed plants.
POLARITY OF INDUCTION AND PATTERN OF PRIMARY PHLOEM FIBER DIFFERENTIATION IN COLEUS
Authors: Aloni Roni
Published: January 2018

The differentiation of primary phloem fibers was studied in Coleus blumei on a quantitative basis. The pattern of fiber differentiation in intact, untreated plants was found to be in the acropetal direction (from a mature internode to a young one). The youngest internodes to differentiate primary phloem fibers were those with cambial activity. In plants grown in the winter, fibers started to differentiate in internodes closer to leaf #2 than in spring‐grown plants. A wound changes the pattern of fiber differentiation surrounding it. A wound in which the tissues above and below it were separated with parafilm, prevented fiber differentiation in the tissues directly below the wound, and caused more fiber differentiation in the tissues above and lateral to it. Under wounds with no parafilm separation, few or many fibers differentiated depending on the angle of the wound. The number of fibers under diagonal wounds was five to nine times more than under a horizontal wound. By excision experiments it was found that mature leaves were the source of induction of fiber differentiation. Leaves that produced induction caused fiber differentiation in the internode below them but did not cause fiber differentiation in the internode above. The induction, which can flow through a wound and cause fiber differentiation in at least two internodes below the source, is a polar induction in the basipetal direction (i.e., in the direction from the leaves to the root). Phloem fibers differentiated only in the vascular strands and not from the parenchyma cells between the strands. Therefore, they follow the new regenerative sieve and vessel elements in the pre‐existing vascular strands, but do not follow them in their regeneration between the longitudinal strands.
ACHLAMYDOCARPON VARIUS COMB. NOV.: MORPHOLOGY AND REPRODUCTIVE BIOLOGY
Authors: Taylor Thomas N. , Brack‐Hanes Sheila D.
Published: January 2018

Structurally preserved arborescent lycopsid fructifications are described from Pennsylvanian age strata in eastern Kentucky and southern Illinois. Achlamydocarpon varius comb. nov. is the name proposed for these cones and previously reported isolated megasporophylls described as Lepidostrobophyllum varius. The specimens range up to 3.5 cm long and represent cone apices. Megasporophylls are spirally arranged and attached to the cone axis at an acute angle. Megasporangia are large with a wall two cell layers thick. Each sporangium contains one large, presumably functional megaspore, and three smaller, abortive megaspores. Functional and abortive spores possess a prominent apical tuft (massa) that covers up to one‐third of the proximal surface of the spore. Sporoderm ultrastructure is detailed together with a comparison of morphologically similar sporae dispersae megaspores. The possible function of the megaspore massa is discussed as it relates to the reproductive biology of the cone.
PRODUCTIVITY AND COMPOSITION OF A BALDCYPRESS‐WATER TUPELO SITE AND A BOTTOMLAND HARDWOOD SITE IN A LOUISIANA SWAMP
Authors: Conner William H. , Day John W.
Published: January 2018

The productivity and composition of two study sites in a southern Louisiana freshwater swamp were studied from October 1973 to November 1974. Net productivity was determined from measurements of litter‐fall, stem growth of woody species, and harvest samples of annual herbaceous understory. Annual stem growth was calculated from biomass estimates on two different dates. The annual increase in stem biomass was 800 g dry wt/m2 for a bottomland hardwood site (BLH) and 500 g dry wt/m2 for a baldcypress‐water tupelo site (CT). Litter‐fall was 574 g dry wt/m2/yr for BLH and 620 g dry wt/m2/yr for CT. Harvest samples within the two plots yielded 200 g dry wt/m2 and 20 g dry wt/m2 for BLH and CT, respectively. Minimum net primary production was calculated as the sum of the three: 1574 g dry wt/m2/ yr for BLH and 1140 g dry wt/m2/yr for CT. Maximum estimates of herbaceous production and insect consumption were made by using values from the literature. Estimated total net primary productivity was 1733 g dry wt/m2/yr for BLH and 1516 g dry wt/m2/yr for CT. Tree composition was determined by the point‐centered quarter method. Relative frequency, relative density, absolute density, relative dominance, and importance value (IV) were calculated for the tree species along each transect. In the bottomland hardwood area many woody species exist with Acer rubrum var. drummondii (IV = 23.9) and Nyssa aquatica (IV = 18.4) the most dominant. In the baldcypress‐water tupelo area, fewer woody species exist and Taxodium distichum (IV = 39.2) and N. aquatica (IV = 37.6) dominated. Comparison of productivity data from several southeastern swamps indicate that flowing water regimes tend to result in the highest swamp forest productivity.
AN ELECTRON MICROSCOPIC EVALUATION OF CYTOHISTOLOGICAL ZONATION IN THE SHOOT APICAL MERISTEM OF PINUS BANKSIANA
Authors: Cecich Robert A.
Published: January 2018

Shoot apical meristems of jack pine (Pinus banksiana) were examined by light and electron microscopy. Cytohistological zonation was evident when meristems were fixed in Craf IV, embedded in paraffin, and stained with Chlorazol Black E. When meristems were fixed for electron microscopy the cytoplasm of the apical initials and central mother cells each contained numerous lipid bodies and their nuclei contained little, if any, heterochromatin. The cytoplasm of the peripheral zone was rich in ribosomes. The nuclei of the peripheral zone and rib meristem were heterochromatic. Thus, the lack of heterochromatin in the nuclei and the dissolution of lipids in the cytoplasm of the apical initials and central mother cells appeared to contribute most to the organization and appearance (cytohistological zonation) of the shoot apex when standard histological techniques are used.
THE CUTICULAR ANATOMY OF FRENELOPSIS VARIANS FROM THE LOWER CRETACEOUS OF CENTRAL TEXAS
Authors: Daghlian Charles P. , Person Christopher P.
Published: January 2018

Stem fragments identified as Frenelopsis varions Fontaine have been found in the Lower Cretaceous (Albian) of central Texas. The cuticle is extremely thick and characterized by 5–6 subsidiary cells with papillae overarching the stomatal chamber. Guard cells are deeply sunken below the epidermis. Stomatal complexes are arranged in axial rows extending from the base of an internode to its apex. The rows of stomata continue into the sheathing leaf where the rows curve towards the leaf apex. The epidermis of F. varions was apparently long persistent and underwent prolonged growth. Axial rows of stomata are frequently disrupted resulting in a random pattern of stomata. A single, highly reduced, sheathing leaf is present at each node. The margin of the leaf has numerous unicellular trichomes and extends to form a slightly triangular blade.
HORMONAL REQUIREMENTS OF EXCISED DIANTHUS CARYOPHYLLUS L. SHOOT APICAL MERISTEM IN VITRO
Authors: Shabde Meena , Murashige Toshio
Published: January 2018

Whereas a medium containing kinetin alone enabled a few Dianthus caryophyllus L. apical meristem dome explants to develop into rooted plants, the highest frequency of plants was obtained in one containing supplements of both IAA and kinetin. In an unsupplemented medium, continued development required that explants have 2 pairs of primordial and a pair of expanding leaves. Kinetin alone caused production of many new leaves, but the development was significantly less than when it was furnished in combination with IAA. IAA given alone caused meristem explants to develop primarily callus, roots, and a few leaves. Gibberellin and abscisic acid were without promotive effects on leaf and shoot formation. A balance of hormonal substances, synthesized in young leaf structures and relocated to the meristem, is proposed as the fundamental mechanism that regulates new leaf initiation in the shoot apex.
STUDIES OF THE MONOTROPOIDEAE (ERICACEAE). FLORAL NECTARIES: ANATOMY AND FUNCTION IN POLLINATION ECOLOGY
Authors: Wallace Gary D.
Published: January 2018

The morphological and vascular characteristics of the nectaries of the species of the Monotropoideae (Ericaceae) reflect the morphology and declination of the flowers. These, in turn, are related to the pollination systems of the species. The nectaries of members of the Monotropoideae exhibit a range in form from slender, elongate projections, to short, stout ones, or to low ridges between the staminal bases.
ANATOMICAL STUDIES OF CYATHEA AND TRICHIPTERIS (CYATHEACEAE)
Authors: Lucansky Terry W.
Published: January 2018

Comparative anatomical studies of the mature stems of two species each of Trichipteris and Cyathea (Cyatheaceae) are described. The outermost boundary of the stem is typically a two‐layered hypodermis. Mucilage‐sac cells are randomly distributed in all parenchymatous areas of the stem and form articulated laticifer systems. Localized areas of sclerenchyma tissue occur in the cortex of both T. microphylla and C. suprastrigosa. All species studied possess medullary bundles, whereas cortical bundles are found only in T. trichiata. Accessory bundles occasionally are associated with indentations in the internal stelar sheath of T. trichiata. The stelar pattern in each genus is a dictyostele and consists of individual meristeles. Distinctive cubical cells typically occur wherever sclerenchymatous fibers and parenchyma cells abut one another. Tangential cells occur within the primary phloem of each meristele, and occasionally within the larger accessory bundles. The primary xylem of the adventitious roots is typically diarch, although triarch and tetrarch xylem may occur. Leaf traces and petiole strands are similar anatomically to the accessory bundles. Based upon this study Trichipteris and Cyathea show striking anatomical similarities, and appear to be closely‐related taxa.
DOES ARCTOSTAPHYLOS UVA‐URSI (BEARBERRY) HAVE NITROGEN‐FIXING ROOT NODULES?
Authors: Tiffney W. N. , Benson D. R. , Eveleigh D. E.
Published: January 2018

An earlier report of the presence of Alnus‐type nitrogen‐fixation root nodules on Arctostaphylos uva‐ursi (bearberry) has been re‐examined. Nodular structures, externally resembling those of alder, were observed at four locations in eastern North America and in northern Scotland. No endophytes could be found in these structures and repeated assays by the acetylene reduction technique failed to demonstrate their ability to fix dinitrogen in North American material. The structures, in microscopic section, possessed typical bud morphology, could be sprouted in a moist chamber and produced shoots under stressed conditions in the field. The suspected 'nodules' are probably latent buds, serving to re‐establish bearberry plants following damage.
MORPHOLOGY OF TEOSINTOID AND TRIPSACOID MAIZE (ZEA MAYS L.)
Authors: de Wet J. M. J. , Harlan J. R. , Randrianasolo A. V.
Published: January 2018

Modern races of maize (Zea mays L.) are characterized by indurated glume and rachis tissues. The archaeological record, as well as experimental studies indicate that in North America this induration is associated with hybridization between domesticated maize and its closest wild relative Z. mays subsp. mexicana (Schrad.) Iltis (teosinte). Similar induration can also be introduced into maize through introgression from Tripsacum. North and South American indurated races of maize are not all closely allied morphologically. They evolved independently under domestication. Teosinte is absent from South America, but Tripsacum is widely sympatric with maize from about 42 N to 42 S latitude. For these reasons it has been postulated that induration in South American races may be the result of Tripsacum introgression. However, barriers restricting gene exchange between Zea and Tripsacum are difficult to overcome in nature. It is maintained that indurated South American races of maize were derived from indurated Mexican races, and that the presence or absence of such induration is due to different degrees of expression by intermediate alleles of the tunicate locus.
ASCI OF THE PEZIZALES III: THE APICAL APPARATUS OF EUGYMNOHYMENIAL REPRESENTATIVES
Authors: Samuelson Don A.
Published: January 2018

Morphological, developmental and cytochemical examinations were made with light and electron microscopy on the apical apparatuses of four eugymnohymenial species, Pyronema domesticum, Ascodesmis sphaerospora, Coprotus winteri and C. lacteus. Ascal tips in all four species were notably thinner walled than the rest of the ascus. Ultrastructurally, demarcation of the opercula was enhanced after staining with silver methenamine. Wide zones of dehiscence are formed in the outer layer of A. sphaerospora and C. winteri. In P. domesticum the outer layer of the operculum is differentially stained from the rest of the ascal wall. Wall dimensions in the multispored asci of C. winteri are approximately three times greater than those in the eight‐spored asci of C. lacteus. The shape of the apical apparatus of C. lateus is almost identical to that of C. winteri. Morphological and cytochemical similarities of the apical apparatuses in Ascodesmis, Pyronema and Coprotus help demonstrate greater relationship between these taxa and support the belief that these taxa are most closely related to members of the Otideaceae and Aleuriaceae.
TRIGONOCARPUS LEEANUS, A NEW SPECIES FROM THE MIDDLE PENNSYLVANIAN OF SOUTHERN ILLINOIS
Authors: Gastaldo Robert A. , Matten Lawrence C.
Published: January 2018

A new species of Trigonocarpus Brongniart is described from the level of the Herrin (No. 6) Coal (Carbondale Formation, Kewanee Group) at Carterville, Illinois. The seed is three dimensionally preserved by authigenic cementation and exhibits a well preserved nucellar cast, integument and micropylar region. The specimen represents the largest pteridosperm compression‐impression seed collected in North America and measures 10 cm from the apex of the micropyle to the chalazal end, and at least 5 cm in breadth. Trigonocarpus leeanus sp. n. is compared to the remaining forty‐three taxa within the genus, and specifically with Trigonocarpus grandis Lesquereux, the one species with dimensions approaching it. An emended diagnosis, with designation of a lectotype, is presented for Trigonocarpus grandis. Correlation of the features displayed by Trigonocarpus leeanus sp. n. and the petrified taxa within Pachytesta Brongniart is attempted.
THE RELATIVE COSTS OF SELF‐ AND CROSS‐FERTILIZED SEEDS IN IMPATIENS CAPENSIS (BALSAMINACEAE)
Authors: Waller Donald M.
Published: January 2018

By using a generally applicable technique that involves monitoring the development and survivorship of flowers and seed capsules, I estimated the material and energetic costs of producing self‐ and cross‐fertilized seeds in Impatiens capensis. All flowers and fruits on six plants were censused intensively for the two‐month period of reproduction. Cleistogamous (selfing) flowers ripened seed in about 24 days, compared to about 36 days for the chasmogamous (outcrossing) flowers. In terms of dry weight, selfed seeds cost about two‐thirds as much as outcrossed seeds: 12.4 versus 18.4 mg dry weight per seed. When adjusted to the currency of calories, and including an independent estimate of pollen and nectar production in outcrossing flowers, I estimate the costs to be about 65 and 135 calories per selfed or outcrossed seed. Sources of error include the accuracy of the estimates of flower and fruit weight, and possible differences among the developmental stages in respiratory costs. The cost discrepancy implies that outcrossed seeds should possess a countervailing fitness advantage large enough to offset their greater energetic cost.
ON THE CYTOLOGY OF ANTHERIDIUM FORMATION IN THE FERN SPECIES ONOCLEA SENSIBILIS. I. CYTOLOGY OF CELL PLATE AND CELL WALL FORMATION
Authors: Leung Cecilia , Näf Ulrich
Published: January 2018

In the four‐celled antheridium of the fern species Onoclea sensibilis a central spermatogenous cell is enveloped by a jacket of three cells. Starting from the base, the jacket comprises the cup‐shaped basal cell, the ring cell—both of which encircle the spermatogenous cell—and the cap cell. The lower wall of the spermatogenous cell has the configuration of a funnel; its upper wall is dome shaped. The choice of whole antheridia for study instead of sectioned ones has, for the first time, made it possible to study the formation of the uniquely shaped antheridial cell plates step by step. The cell plate antecedent of the funnel wall has the configuration of a funnel. This conclusion conflicts with Davie's contention that this cell wall is oriented transversely at first and acquires funnel‐shape secondarily. The present studies further show that the funnel cell plate forms from base to rim. This finding contrasts with a report that in another fern species this cell plate begins to form on one side of the initial and then proceeds circularly around it. The base of the funnel cell plate attaches to the basal wall of the antheridium initial in a separate event. The genesis of the dome‐shaped upper wall of the spermatogenous cell is described for the first time.
BIOCHEMICAL AND MORPHOLOGICAL EFFECTS OF TEMPERATURE ON TYPHA LATIFOLIA L. (TYPHACEAE) ORIGINATING FROM DIFFERENT ENDS OF A THERMAL GRADIENT. I. CONTROLLED ENVIRONMENTAL STUDIES
Authors: Jones J. C. , Hancock J. F. , Liu E. H.
Published: January 2018

T. latifolia grows along most of the shoreline of Par Pond, a cooling reservoir for the reactors at the Savannah River Plant in Aiken, South Carolina. A thermal gradient exists because of the movement of hot water from one end of the pond to the other. This study was undertaken to determine the biochemical and morphological effects of temperature on Typha latifolia clones originating from different ends of this thermal gradient. The data indicated that both “hot” and “cold” end plants react similarly to temperature. Forty‐eight rhizome plants from both ends of Par Pond were transplanted into tanks at 20 C and 30 C. Total levels of malic dehydrogenase activity, proportions of mitochondrially bound MDH and growth rates were significantly different in plants grown in the two tanks, but no significant differences were observed within each tank between individuals from the “hot” and “cold” end. The relation of these results to hypotheses concerning quantitative strategies of enzyme adaptation are discussed in the paper.
NUMBERS AND DISTRIBUTIONS OF VASCULAR BUNDLES IN SCAPES OF THREE ALLIANCES OF THE GENUS ALLIUM L. (LILIACEAE)
Authors: Jacobsen T. D.
Published: January 2018

The arrangement and numbers of vascular bundles were documented for the species of the Allium cernuum Roth, Allium validum Wats., and Allium kunthii G. Don alliances. These characters proved consistent and diagnostically useful in the A. cernuum and A. validum alliances, but inconsistent in the A. kunthii alliance.
A STRUCTURAL AND FUNCTIONAL STUDY OF THE COORDINATED REACTIONS OF INDIVIDUAL COMMELINA COMMUNIS L. STOMATA (COMMELINACEAE)
Authors: Saxe Henrik
Published: January 2018

Opening and closure movements of individual stomata were analyzed by light microscopy, scanning electron microscopy, and time‐lapse photomicrography. Turgor‐pressure‐induced changes in pore shape of Commelina communis L. stomata were observed in vivo and in fixed material. The ventral wall of the guard cells undergoes three‐dimensional alterations during opening and closing. Stomatal aperture increases with increase in light intensity and with decrease in CO2 concentration as previously described, while reactions to relative humidity and anaerobiosis are somewhat divergent from common experience. Low humidity induces opening rather than closure of stomata in well watered greenhouse plants, and lack of oxygen induces consecutive opening and closure movements. Individual stomata characteristically open by three distinct steps: (1) rapid opening; (2) immobility or slow closure; (3) relatively rapid opening. Since the timing of the second step varies for individual stomata, it is obscured by methods that integrate the responses of several stomata. The movements of individual stomata are well synchronized, but active communication between stomata in different areas can not be confirmed.
ULTRASTRUCTURE OF PARAQUAT‐TREATED SLASH PINE (PINUS ELLIOTTII ENGELM.)
Authors: Birchem Regina , Brown Claud L.
Published: January 2018

The introduction of paraquat (l, 1‘‐dimethyl‐4,4‘‐bipyridylium ion) into the transpiration stream of young slash pine (Pinus elliottii Engelm.) trees significantly enhances oleoresin biogenesis and results in localized resin soaking in treated portions of the bole. All affected cells of the xylem symplast, including those not directly associated with resin ducts, begin to synthesize excessive oleoresin and secrete or lose it initially through pits into the lumen of contiguous tracheids. Oleoresin is observed in plastids, mitochondrial envelopes, vacuoles, and ER cisternae in both control and treated trees. Cells near the site of paraquat treatment show extreme damage to membrane integrity, depletion of starch, and loss of cellular organization. The transport of oleoresin across cellular membranes does not appear to be achieved by transporting vesicles or by a mechanism involving exocytosis. Although oleoresin is observed in various cellular organelles, it is unclear if its synthesis occurs in association with these organelles or whether this compartmentation results from random contact and solubilization of this lipophilic material in the membranes of different organelles.
REPRODUCTIVE PHYSIOLOGY IN THE SEAGRASS, SYRINGODIUM FILIFORME, FROM THE GULF OF MEXICO AND THE CARIBBEAN
Authors: McMillan Calvin
Published: January 2018

Reproductive physiology in Syringodium filiforme Kütz. is controlled primarily by temperature under day lengths ranging from 12 hr to continuous light. Texas plants can be induced to flower at temperatures ranging from 20 to 24 C, but southern Gulf of Mexico and Caribbean plants are most readily induced at 23–24 C. Texas plants proceed to anthesis at temperatures above 22 C, but St. Croix plants require higher temperatures, above 25 C, for emergence of flowers from the bracts. Flowers induced under continuous light proceed to anthesis under day lengths shortened to 11 hr, but further floral induction is inhibited even under inductive temperatures. In natural seagrass beds, flowering occurs primarily under lengthening day lengths and warming temperatures that follow winter minima, but inflorescences may occur at other times of the year if temperatures permit.
THE ASSOCIATION OF DRUSE CRYSTALS WITH THE DEVELOPING STOMIUM OF CAPSICUM ANNUUM (SOLANACEAE) ANTHERS
Authors: Horner Harry T. , Wagner Bruce L.
Published: January 2018

Each of the two stomiums in the anther of Capsicum annuum (sweet pepper) consists of a single layer of cells immediately below the epidermis between two adjacent locules. Each stomium extends the entire length of the anther and splits open at pollen maturity. Many calcium oxalate druse crystals form within the vacuoles of the stomium cells in association with membrane complexes and paracrystalline bodies. These latter structures are reported here for the first time and each is considered to be a nucleation site for druse crystal formation. Prior to the appearance of membrane complexes and crystals within the vacuoles, plasmalemmasomes are visible next to the stomium cell walls and contain vesicles and fibrous material. We propose that these bodies carry wall materials, including calcium ions and possibly oxalate ions, into the vacuoles. Their presence coincides with crystal formation. Two other types of crystals occur in the connective tissue between stomiums and the single vascular strand. These crystals, along with those in the two stomiums, form at precise times during anther development. Contrary to the more numerous suggestions that crystals protect against predators or are metabolic waste products, we believe their formation aids in degradation and weakening of the cell walls between the locules and, thus, contributes to the release mechanism for the pollen.
THE AMINO ACIDS OF EXTRAFLORAL NECTAR FROM HELIANTHELLA QUINQUENERVIS (ASTERACEAE)
Authors: Inouye David W. , Inouye Richard S.
Published: January 2018

The extrafloral nectar from involucral bracts of Helianthella quinquenervis has more nonprotein (5) and total (24) amino acids than have been reported for any other extrafloral nectar. Seven to twelve additional unknowns, probably nonprotein amino acids, were also found. The concentrations of amino acids (8–10 on the histidine scale) were the highest ever reported for extrafloral nectar. Most amino acids were found in all samples, while others were variable in their occurrence.
SPORE WALL ULTRASTRUCTURE IN THE LIVERWORT ATHALAMIA HYALINA
Authors: Steinkamp M. P. , Doyle W. T.
Published: January 2018

Mature spores of Athalamia hyalina (Marchantiales, Cleveaceae) were examined with both scanning and transmission electron microscopes. Single, hollow, dome‐like projections, sometimes having small pores and a coarsely granular surface texture, stud the spore surface, usually in a pattern of concentric circles. In section, the spore wall has an intine and two‐layered exine. Intine‐like material separates some lamellae of the inner exine, which is joined to the outer exine around the dome bases. Inner exine lamellae are composed of thin (5–6 nm), closely parallel membrane‐like subunits. The outer exine is formed from a single large highly modified and doubly‐coated lamella, the undulations of which form the surface domes. Dome cavities often are filled with a loose network of granular material.
FLORAL INDUCTION DOES NOT ALTER THE GROWTH PARAMETERS OF FUCHSIA
Authors: Abou‐Haidar Sana S. , Burger David W.
Published: January 2018

Floral induction by night interruption of Fuchsia hybrida cv. Lord Byron, a quantitative long‐day plant with decussate phyllotaxis and an indeterminate flowering habit, altered neither the rate of leaf initiation nor the rate of leaf expansion; nor did flower initiation and development change the vegetative growth of the plants. This was diagnosed using plastochron duration and plastochron ratio measurements before, during, and after a 10‐day induction period. A comparison between indeterminate and determinate flowering is made using these two parameters.
THE ROLE OF ENDOMYCORRHIZAE IN REVEGETATION PRACTICES IN THE SEMI‐ARID WEST. III. VERTICAL DISTRIBUTION OF VESICULAR‐ARBUSCULAR (VA) MYCORRHIZA INOCULUM POTENTIAL
Authors: Schwab Suzanne , Reeves F. Brent
Published: January 2018

The changes in vesicular‐arbuscular (VA) mycorrhiza inoculum potential (MIP) in soil profiles from a mid‐elevation sage community were measured using a corn bioassay. The MIP was significantly reduced below 30 cm depth and approached zero at less than 1 m depth. The decrease in inoculum potential with depth in diluted soils did not always parallel changes in the nondiluted soil, indicating factors other than numbers of inoculum units also may be important in determining the extent of mycorrhiza formation. The relationship of these results to land disturbance and associated dilution of populations of VA mycorrhizal fungi and to defining topsoil is discussed.