bluuebunny/crossref_metadata_2025 huggingface dataset:
THE ROLE OF ENDOMYCORRHIZAE IN REVEGETATION PRACTICES IN THE SEMI‐ARID WEST. I. A COMPARISON OF INCIDENCE OF MYCORRHIZAE IN SEVERELY DISTURBED VS. NATURAL ENVIRONMENTS
Authors: Reeves F. Brent , Wagner David , Moorman Thomas , Kiel Jean
Published: January 2018

A comparison of a natural, undisturbed ecosystem, a mid‐elevation sage community, with a severely disturbed old roadbed through this community revealed that more than 99% of the plant cover in the natural community was mycorrhizal (vesicular‐arbuscular), whereas less than 1% of the plant cover in the disturbed area (roadbed) was mycorrhizal. Examples of nonmycorrhizal plants as primary successional species in severely disturbed habitats are discussed. The importance of maintaining or re‐establishing the mycorrhizal fungal component in reclamation programs designed to produce stable ecosystems is emphasized.
IN SEARCH OF A PLANT GROWTH PARADIGM
Authors: Burström H. G.
Published: January 2018

Growth by cell divisions in apical meristems is mainly a synthesis of cell matter. Cell divisions in the meristem follow certain patterns, with radial gradients which may be abruptly interrupted. The gradients go in the reverse directions in stem and root apex. The cause of the gradients seems to be unknown, likewise why the patterns are the opposite in stem and root, but they form the foundation of ensuing tissue differentiation. Cell elongation is driven by the metabolic energy of intussusception of new matter in the wall and by the accepted patterns for water fluxes. An attempt has been made to formulate questions which ought to be answered for a better insight into the mechanism of longitudinal growth.
ADVANCES IN THE STUDY OF SO‐CALLED AQUATIC HYPHOMYCETES
Authors: Ingold C. T.
Published: January 2018

Progress in the study of the freshwater aquatic fungal flora (mainly hyphomycetes) of submerged decaying leaves of dicotyledonous trees and shrubs, since the discovery of the flora in 1942, is reviewed. The abundant occurrence of liberated conidia, which tend to be of distinctive form, in persistent foam on a stream is noted and illustrated by an example from Scotland. Developments in the taxonomy of these fungi since 1942 are noted. About 60 genera and around 120 species are now recorded. In a number the perfect stage has been discovered. In most cases it has proved to be an ascomycete, but it is sometimes a basidiomycete. Conidium development in aquatic hyphomycetes is discussed in the light of recent views on the classification of conidial types. It is argued that the most valid distinction is between phialoconidia and other types, rather than between those of blastic and those of thallic development. Dispersal is discussed with special reference to upstream spread and the problem of dispersal from one isolated water system to another. Finally, attention is given to the ecology and general physiology of these fungi. Their possible importance in processing decaying leaves for subsequent consumption by small aquatic animals is considered. The terrestrial occurrence of many “aquatic hyphomycetes” is noted and it is suggested that “amphibious hyphomycetes” might be a better term.
C‐GLYCOSYLFLAVONES IN THE GNETOPSIDA: A PRELIMINARY REPORT
Authors: Wallace James W.
Published: January 2018

C‐Glycosylflavones appear to be the only detectable flavonoids in representative species of Gnetum, Ephedra and Welwitschia. Ephedra antisyphilitica contains mixed 6,8‐di‐C‐glycosides of apigenin and luteolin and Welwitschia mirabilis produces 6‐C‐glycosylchrysoeriol and 6,8‐di‐C‐glycosylchrysoeriol. Recently it was reported that Gnetum gnemon contains 6‐C‐, 8‐C and 6,8‐di‐C‐glucosyl derivatives of apigenin, luteolin and their 7‐0‐methyl ethers. Based on the present preliminary survey the apparent absence of other flavonoid types indicates that C‐glycosylflavones may be a unifying characteristic of the Gnetopsida.
A NEW METHOD FOR EXAMINING INDUCTION OF MOSS BUDS BY CYTOKININ
Authors: Nehlsen Wllla
Published: January 2018

Protonemata of Polytrichum juniperinum were grown in the dark, in sucrose‐ and cytokinin‐supplemented media. Under these conditions gametophore buds form shortly after spore germination. Of the cytokinins tested, DMAAP was most effective in bud induction. This system holds much promise for study of cytokinin action.
BRANCH GEOMETRY AND EFFECTIVE LEAF AREA: A STUDY OF TERMINAUA‐BRANCHING PATTERN. 1. THEORETICAL TREES
Authors: Fisher Jack B. , Honda Hisao
Published: January 2018

Single lateral branches and branch tiers of Terminalia catappa L. are simulated and drawn by computer. Leaf clusters on the branches are approximated by discs, and the effective leaf areas are determined by use of Dirichlet domains. Theoretical optimal branching angles which produce the maximum effective leaf area are obtained from simulations. Symmetrical and asymmetrical branching angles are contrasted; the latter characterize real trees. Varying leaf disc radius and ratio of branch‐unit lengths affects optimal branching angles, as does the symmetry of a tier of five branches. Leaf area indices for individual branches and branch tiers are given for all simulations. The number of branches in a tier has a major effect on leaf area index and effective leaf area. The theoretical optimal branching angles of many simulations are very close to the values observed in real trees of T. catappa. We conclude that the observed branching angles and number of branches in a tier of this species optimize light interception within constraints of a fixed pattern of branching, one that is widespread among tropical trees.
THE SURFACE DECONTAMINATION OF SEEDS TO PRODUCE AXENIC SEEDLINGS
Authors: Sweet Haven C. , Bolton Wade E.
Published: January 2018

A variety of sterilizing agents were tested to develop a standard procedure for surface decontaminating seeds to produce axenic seedlings. The use of calcium hypochlorite (0.5% phosphate buffer, pH 6) for 10 min followed by three sterile water rinses was among the most effective agents, and it did not injure some species as did sodium hypochlorite, formaldehyde, ethylene oxide and mercuric chloride. Some species contained internal microbes requiring severe treatments which killed or injured the seedling, while other species were “decontaminated” with a sterile water rinse. The percentage of seeds with internal microbes varied considerably among plant species, seed lot, and the length of seed storage. Thus, with seeds not easily decontaminated, screening of additional seed lots would be more profitable than testing additional decontamination agents. Release of microbes from the seed's interior is associated with germination, and microbial testing must last at least 11 days. Nutrient agar permitted growth, although the seedlings outgrew petri plates too quickly for adequate certification. These seedlings were transferred to nutrient agar in quart jars in which an internal pool of broth was periodically agitated to permit microbial sampling of the leaves while the plant grew.
DISTRIBUTION OF CALCIUM OXALATE CRYSTAL IDIOBLASTS IN CORMS OF TARO (COLOCASIA ESCULENTA)
Authors: Sunell Leslie A. , Healey Patrick L.
Published: January 2018

The morphology and distribution of intracellular crystals of calcium oxalate in taro (Colocasia esculenta) was studied by light microscopy. The modified Pizzolato (AgNO3‐H2O2) method was used to localize crystals in cleared corm cross sections. Crystals of two forms were found: druses and raphides. The numbers and density of the crystals in corms increase rapidly in early development, then level off, and eventually decrease in older and larger corms. An especially high concentration of druses was observed 2‐3 mm from the exterior edge of many corms. This corresponds to a ring of vascular tissue which circumscribes the corm at approximately the same distance from the surface. Observations suggest that the development of these highly specialized cells and the formation of calcium oxalate crystals is a dynamic process.
ROOT GLOCHIDS AND ROOT SPURS OF OPUNTIA ARENARIA (CACTACEAE)
Authors: Boke Norman H.
Published: January 2018

Root glochids of Opuntia arenaria Engelm. are produced by adventitious buds (areoles) that arise endogenously on fleshy roots. If they remain active, root areoles become dwarf shoots that initiate only glochids and trichomes unless the roots are uncovered or the shoots bearing the roots are removed. Then they will expand, producing aerial shoot joints. Root spurs are formed in great numbers on the profusely branched system of small roots. They consist of clusters of rootlets about one mm long that are initiated in sympodial sequence, each new rootlet arising endogenously near the base of the preceding one. On older spurs this results in the formation of a short axial peg. Rootlet primordia lack a root cap from the beginning and appear to mature quickly, losing all their meristematic characteristics and becoming completely covered with root hairs, even over the tip. They may represent a mechanism for the rapid production of root hairs during the infrequent periods when moisture is available. In any case, they seem to be transitory structures because cork soon forms beneath the older ones on a spur.
THE FLAVONOIDS OF ONAGRACEAE: TRIBE EPILOBIEAE
Authors: Averett John E. , Raven Peter H. , Becker Hans
Published: January 2018

Data for the flavonoids of each of the species of Boisduvalia and each of the 14 species of Epilobium that constitute the 5 sections except for sect. Epilobium are presented. An analysis of nearly 100 populations showed that 7 flavonol 3‐O‐glycosides based on kaempferol, quercetin, or myricetin aglycones are present among the several species. All 7 compounds are present in each of the 2 genera but certain patterns of variation, especially in the loss of arabinosides, are noted among the several sections of the two genera. An intersectional comparison of the variation correlates flavonoid patterns more with the relative evolutionary advancement of specialization of the taxa than with their phyletic relationships. Further, a trend of decreased glycosylation with advancement within the tribe is documented. Both points are contrary to what is generally assumed for flavonoids in evolutionary studies.
CREOSOTE BUSH: LONG‐LIVED CLONES IN THE MOJAVE DESERT
Authors: Vasek Frank C.
Published: January 2018

Creosote bush clones in the Mojave Desert develop by irregular radial growth, stem segmentation and the production of new stems at the outer edge of stem segments. The resulting circular clone encloses a central bare area as the central dead wood rots away. Old clones become elliptical and may exceed 20 m in length. Modern growth rates estimated from annual increments in stem wood of seedlings (0.73 mm/yr) and young clones (0.82 mm/yr) approximate those estimated for radiocarbon‐dated wood samples (0.66 mm/yr). Assuming comparable growth rates through time, the extrapolated age of the largest known clone (average radius = 7.8 m) may approach 11,700 years. If growth rates have changed, that clone's age may be somewhat less.
FOLIAR NECTARIES OF UNUSUAL STRUCTURE IN LEONARDOXA AFRICANA (LEGUMINOSAE), AN AFRICAN OBLIGATE MYRMECOPHYTE
Authors: Elias Thomas S.
Published: January 2018

Extrafloral nectaries of an African myrmecophyte, Leonardoxa africana (Baill.) Aubr., are disc‐shaped, non‐vascularized, embedded in the leaf mesophyll, and have a tiny neck extending to the abaxial leaf surface. These structural features differ from those found in other members of the Leguminosae, and represent an unusual type among flowering plants. These embedded foliar nectaries apparently have an energetic advantage over external nectaries and their presence supports the idea of independent and repeated evolution of nectaries in the legume family.
A BIOSYSTEMATIC STUDY OF THE POLYGONUM HYDROPIPEROIDES (POLYGONACEAE) COMPLEX
Authors: McDonald Charles B.
Published: January 2018

The Polygonum hydropiperoides complex includes P. hydropiperoides Michx., P. opelousanum Riddell ex Small, P. setaceum Baldwin ex Ell., and P. hisutum Walter. Studies of morphology, cytology, and crossing compatibility were conducted with specimens from North Carolina, South Carolina, Georgia, and Florida. A multivariate cluster analysis using 212 specimens and 34 characters indicated that P. hirsutum and P. setaceum are each morphologically distinct while P. hydropiperoides and P. opelousanum are morphologically indistinct from one another. The chromosome counts of 2n = 20 for P. setaceum and P. hirsutum, and 2n = 40 for P. hydropiperoides and P. opelousanum are the first reported for the respective species. Experimental hybridizations produced the fertile hybrids P. hydropiperoides x opelousanum and P. setaceum × hirsutum. Results of these studies and population structure, habitat, and pollination studies suggest that P. hydropiperoides, P. setaceum, and P. hirsutum are each distinct species while P. opelousanum is indistinct and should be merged with P. hydropiperoides.
THE ZOOSPORE OF CHLOROKYBUS ATMOPHYTICUS, A CHAROPHYTE WITH SARCINOID GROWTH HABIT
Authors: Rogers Catherine E. , Mattox Karl R. , Stewart Kenneth D.
Published: January 2018

Chlorokybus atmophyticushas a sarcinoid growth habit and produces scale‐covered zoospores. Flagella are laterally inserted and attached internally to a multilayered structure characteristic of the Charophyceae. There are two kinds of pyrenoid in each cell, a feature previously observed in only one scaly green flagellate.C. atmophyticusdemonstrates that the sarcinoid growth habit arose independently at least twice in the green algae and cannot be used to define taxonomic groups unless combined with other criteria. It is further concluded thatC. atmophyticusshould be classified in a separate family Chlorokybaceae and a separate order Chloroky bales.
STIGMA, STYLE, AND OBTURATOR OF ORNITHOGALUM CAUDATUM (LILIACEAE) AND THEIR FUNCTION IN THE REPRODUCTIVE PROCESS
Authors: Tilton Varien R. , Horner Harry T.
Published: January 2018

Transmitting tissue in Ornithogalum is divided into three regions corresponding to classical divisions of the gynoecium: stigma, style, and ovary. The stigma differentiates from epidermal cells of the stylar apex. These cells form the stigmal papillae and have dense cytoplasm with abundant ER and lipid bodies. Papillae have walls with small transfer‐ingrowths. At floral receptivity, papillae secrete a small amount of surface exudate. Epidermal cells of the style contain numerous spherosomes and have thin filaments of cytoplasm traversing the central vacuole. The stylar cortex is composed of 3‐6 layers of parenchyma cells which contain numerous spherosomes and often have secondary vacuoles. Vascular tissue in the style consists of one collateral bundle in each lobe. Cells of the epidermal layer lining the stylar canal are secretory. They are initially vacuolate but fill progressively with dense cytoplasm as their secretory activity increases. Secretory activity occurs in three phases, each characterized by a particular organelle population and secretory product. At anthesis, the canal is filled with an exudate consisting of carbohydrate, protein, and lipid. In the ovary, the obturator differentiates from cells at the base of the funiculus and the tip of the carpel margins. It forms a pad of tissue which covers most of the former placenta. The obturator is secretory and produces a surface exudate. We believe our observations on Ornithogalum support the hypothesis that all transmitting tissue is of the same morphological origin and that it provides nutritive and chemotropic factors for pollen tube growth.
A CYTOGEOGRAPHIC STUDY OF CHAENACTIS DOUGLASII (COMPOSITAE, HELENIEAE)
Authors: Mooring John S.
Published: January 2018

Analysis of 512 plants derived from 200 populations shows that the widely distributed western North American Chaenactis douglasii species‐complex consists of diploids (n = 6), triploids, tetraploids, and hexaploids. Microsporocytes were the source of most of the chromosome counts. About 9% of all plants examined had one or more full‐sized extra chromosomes. Multivalents, usually a ring or chain of four chromosomes, were almost entirely restricted to polyploids, where one or more were identified in 38% of the tetraploids and 33% of the hexaploids. With two exceptions, diploids and polyploids were not found in the same population. Frequencies of diploid, triploid, tetraploid, and hexaploid populations were, respectively, 34, 1.5, 55 and 9.5%. With significant exceptions, diploid populations predominate in the Pacific and Rocky Mountain Systems, whereas polyploid ones are most frequent in the intervening plateaus. Ploidy level is correlated with age of substrate, rather than with climate, elevation, vegetation, or soil type. Range, morphology, ploidy level, and meiotic behavior suggest that var. achilleifolia tetraploids and hexaploids are descendents of hybrids between other variants of the complex. The diploid‐tetraploid‐hexaploid geographic distribution and the age of the substrates where each tends to occur suggest that the complex evolved in late Cenozoic time in response to major climatic and geologic changes that induced migration and hybridization. The hybrid derivatives, stabilized by polyploidy and tolerant of increasing aridity, came to occupy newly available habitats in areas disturbed by volcanic activity and glacial or glacial‐related processes.
POLLEN FLOW AND FECUNDITY IN POPULATIONS OF LITHOSPERMUM CAROLINIENSE
Authors: Weller Stephen G.
Published: January 2018

Stigmatic pollen loads of pin and thrum forms of distylous Lithospermum caroliniense (Walt.) MacMill. generally have very large proportions of incompatible pollen grains. Assortative pollination probably results from large components of self‐pollination rather than geitonogamous pollinations, because pollen loads of large and small individuals are the same, although large individuals would be expected to experience more geitonogamous pollinator flights than small individuals. The distylous reproductive system appears relatively insensitive to changes in pollinator activity and preferential pollen flow between pins and thrums cannot be demonstrated. In contrast to the relatively uniform proportions of pin and thrum pollen on stigmas, absolute pollen loads vary substantially in different years and localities. Extremely low fecundity, which appears to be characteristic of this species, may result in part from lack of pollinator activity. However, even under optimal conditions for pollination, fecundity is less than 20%. Although L. caroliniense appears to have an inefficient pollination system, intrinsic low fecundity may represent a more critical feature of the life history.
ABSORBING TRICHOMES IN THE PLEUROTHALLIDINAE (ORCHIDACEAE)
Authors: Pridgeon Alec M.
Published: January 2018

Glandular trichomes occur on both surfaces of leaves of all examined genera and species of the subtribe Pleurothallidinae (Orchidaceae). Trichome initiation is effected by one periclinal division of a protodermal cell, producing a thin‐walled, globose apical cell with a relatively large nucleus and a subapical stalk cell with heavily cutinized lateral walls. In some species a second periclinal division produces a third small basal cell also having thick lateral walls but thin transverse walls. As leaf development proceeds, the trichome apparatus assumes a sunken position due to continued anticlinal divisions of protoderm. Prior to laminar expansion and guard‐mother‐cell division on the abaxial surface, the wall of the apical cell ruptures and is replaced by a brown opaque residue. Finally, after vascular tissue differentiation and the cessation of meristematic activity, two or more pitted foot cells develop at the base of the trichome and adjacent to the water‐storing hypodermal layers. Preliminary investigations indicate that the trichome apparatus is absorptive throughout its development and similar in function to tillandsioid scales in Bromeliaceae.
DORMANCY IN SEEDS OF FRASERA CAROLINIENSIS (GENTIAN ACEAE)
Authors: Threadgill Paul F. , Baskin Jerry M. , Baskin Carol C.
Published: January 2018

In freshly matured seeds of the long‐lived monocarpic perennial, Frasera caroliniensis Walt., the embryos are underdeveloped and physiologically dormant. Dormancy was broken by a long period of stratification (chilling) at 5 C. Seventy six percent of the seeds germinated at 20 C (day)/10 C (night) after 98 days of chilling at 5 C, while seeds kept at 5 C germinated to 87% after 205 days. A warm, moist pretreatment was not required for subsequent breaking of dormancy at 5 C. Embryos in fresh seeds averaged 1.3 mm long, but after 12 weeks of chilling they averaged 4.1 mm. Thus, the embryos require a period of chilling to become fully developed, after which seeds can germinate at the afterripening temperatures (5 C) or at some higher temperature. Seeds of F. caroliniensis fit Nikolaeva's (1977) morpho‐physiological complex dormancy type.
THE INFLUENCE OF LOW PLANT WATER POTENTIAL ON THE GROWTH AND NITROGEN METABOLISM OF THE NATIVE CALIFORNIA SHRUB LOTUS SCOPARIUS (NUTT. IN T & G) OTTLEY
Authors: Nilsen Erik Tallak , Muller Walter H.
Published: January 2018

Reduced plant water potential, induced by polyethylene glycol in hydroponics, inhibited growth and decreased the number of leaves per branch in the southern California drought‐deciduous species Lotus scoparius (Nutt. in T & G) Ottley. Decreasing plant water potential diminished the proportion of large leaves per branch and therefore reduced the leaf area. Nitrate uptake rate decreased with decreasing water potential, although the nitrate ion concentration increased in the roots and the leaves. Ammonium ion concentration increased significantly in the roots at −5 bars and lower osmotic potentials in the root medium. Kjeldahl nitrogen remained the same in all treatments and tissues over the experimental period. It is suggested that the increase in ammonium ion in the roots was due to a decreased rate of ammonium transport caused by low plant water potential. The slight increase in nitrate ion in the roots may correspond to a decrease in nitrate reductase activity. This study indicates that some of the changes in nitrogen metabolism associated with low water potentials in agricultural plants occur also in a plant which experiences frequent droughts in its native habitat.
MITOTIC ACTIVITY AT THE SHOOT APEX OF AZOLLA FILICULOIDES
Authors: Gifford Ernest M. , Polito Vito S.
Published: January 2018

The mosquito fern, Azolla filiculoides Lam., was grown in a growth chamber on a nitrogen‐free culture solution at 24 C under the following photoperiod: 16 hr light/8 hr darkness. Shoot tips were fixed every 2 hr for 24 hr to determine the mitotic index for the apical cell, immediate derivatives, and remaining cells to the level of the first leaf or lateral shoot primordium. Mitotic indices were 6.9%, 6.5% and 6.3%, respectively. The colchicine method was employed to determine the cell‐cycle durations and duration of mitosis for the same populations of cells. The cell‐cycle duration and duration of mitosis of the apical cell were 28.2 hr and 2.8 hr, respectively; for the immediate derivatives, 26.7 hr and 2.5 hr; for the remaining cells, 23.6 hr and 2.1 hr. Conclusions: the apical cell is as mitotically active as its immediate derivatives, and there is no evidence of a quiescent apical cell.
VASCULAR PATTERNS IN STEMS OF ARACEAE: SUBFAMILY MONSTEROIDEAE
Authors: French J. C. , Tomlinson P. B.
Published: January 2018

Analysis of stem vasculature in representatives of subfamily Monsteroideae (Araceae) by cinematographic techniques based on serial sections shows three main patterns of organization. One group of five genera (Rhaphidophora, Epipremnum, Amydrium, Scindapsus, Monstera) is characterized by simple vascular bundles and axial bundles which are derived by basal aggregation of small bundles branching from existing axial bundles. Another group of two genera (Stenospermation, Rhodospatha) is characterized by compound vascular bundles which are made by rather irregular association of individual collateral bundles. These two groups correspond to the tribe Monstereae. The last group which corresponds to the tribe Spathiphylleae includes two genera (Spathiphyllum, Holochlamys) with amphivasal vascular bundles which are highly condensed and irregularly anastomosing. In part, this division is correlated with habit and habitat. Some members of the first group resemble genera within the subfamily Pothoideae quite closely and indicate that the two subfamilies are not clearly circumscribed. Compound bundles in Rhodospatha and Stenospermation do not have the precise organization previously reported for the Pandanaceae.
CHROMOSOME NUMBERS IN SOUTH AMERICAN HAPLOPAPPUS CASS. (COMPOSITAE)
Authors: Brown Gregory K. , Clark W. Dennis
Published: January 2018

Chromosome counts are reported for 33 species from all four sections of the genus Haplopappus in South America. These include first reports for 28 species and two putative hybrids. All chromosome numbers reported herein are 2n = 5II, with the exception of H. prunelloides with 2n = 6II. Unlike the North American species, the morphological diversity of South American taxa is not concomitant with chromosomal variation.
MECHANICAL STRESS AND CELL WALL ORIENTATION IN PLANTS. II. THE APPLICATION OF CONTROLLED DIRECTIONAL STRESS TO GROWING PLANTS; WITH A DISCUSSION ON THE NATURE OF THE WOUND REACTION
Authors: Lintilhac Philip M. , Vesecky Thompson B.
Published: January 2018

This paper describes an attempt to present living stem tissue with defined mechanical stress in a spatial configuration which can be easily interpreted in section. We have applied compressive stress to a growing Coleus internode in vivo, using stainless‐steel spring‐clips which act through a double‐edged glass interface of known area.

We have found that cambial activity consisting of cell division and enlargement continues even under applied compressive stress ranging up to 20 atm. Tissue reactions to applied stress are discussed in terms of the equilibration of forces propagating through the tissue before, during, and after the presentation of externally applied stress.
LONGITUDINAL GRADIENTS OF ION TRANSPORT IN CORN ROOTS
Authors: Smith Richard C. , Majeed Iqbal
Published: January 2018

Excised roots of corn, 8 cm long, were mounted for collection of xylem exudate, submerged in aerated, labeled salt solutions, and left while steady‐state exudation developed. After 19 hr, additional portions of the roots were removed and all apical ends which had been severed were sealed with wax. Collection of exudate samples began 1 hr later and continued for 8 hr. The results showed that removal of only 1 cm from the apex of the root reduced the output of rubidium to the exudate by as much as 74%. They also showed that the longitudinal changes in ion contribution to the exudate were not linear, but were closely correlated with the longitudinal gradient of Rb content in the root.
SOME OBSERVATIONS ON THE REPRODUCTIVE BIOLOGY OF GAULTHERIA PROCUMBENS (ERICACEAE)
Authors: Mirick Sally , Quinn James A.
Published: January 2018

The pollination and fruit production of Gaultheria procumbens L. (Ericaceae), an evergreen sub‐shrub, were studied in five woodland sites in New Jersey and one in northeastern Pennsylvania. Pollinator exclusion methods at three of the sites produced no consistent differences in fruit and seed set between enclosed plants and controls. Insect pollinators, almost exclusively bumblebees, were sparse at all sites; visitation rates were about 0.01 bee visits/flower/hr. All fruits examined contained at least 35 seeds, but about half of the pistils examined, from open‐pollinated plants, did not contain enough pollen tetrads on their stigmatic surfaces to fertilize this number of ovules. However, the low average fruit set of 8.2% on open‐pollinated plants was due more to the high mortality of buds prior to anthesis than to inadequate pollination. Bud mortality was high and fruit set low in 3 years of observations at various study sites, indicating that this may be a general pattern for the species in northeastern United States and adjacent Canada. The amount of sexual reproduction showed no consistent relationship to stem density.
THE FLORAL BIOLOGY OF CASSIA DIDYMOBOTRYA AND C. AURICULATA (CAESALPINIACEAE)
Authors: Dulberger Rivka
Published: January 2018

The flowers of Cassia didymobotrya and C. auriculata have three types of fertile anthers that differ in orientation, size, shape, and pollen production. Flowers with right‐handed or left‐handed style deflections, i.e., enantiostylous flowers, occur in the same raceme. In Israel, both species are pollinated by pollen collecting buzzing females of Xylocopa pubescens. Vibrations of the carpenter bee are necessary for release of pollen from poricidal anthers and, in C. didymobotrya, also for absorption of pollen through the stigmatic opening into a cavity of the style tip. The largest anthers supply pollen for pollination. Pollen for consumption by the bee, on the other hand, appears to be supplied by all fertile anthers. This is in contrast to the accepted view of a complete separation of functions in the heteromorphic anthers in Cassia. The pollen/ovule ratio in C. didymobotrya was 55,200, and that in C. auriculata 32,000. Only 0.01% of the pollen produced by a flower was found in the stigmatic pollen load, and this fraction allows for high seed sets. From a comparison of the pollen production and utilization in the Cassia species and in certain distylous plants, it is concluded that heteranthery in Cassia does not confer an advantage in pollen economy. The high pollen/ovule ratios are explained by lack of nectar as well as by the large area on which pollen is deposited on the bee's body relative to the small size of the stigma. Enantiostyly in Cassia is considered as part of a pollination syndrome whose characteristics are outlined. The function of enantiostyly as an outbreeding strategy is discussed. In the two Cassia species, opportunities for self‐ and geitonogamous pollinations and self‐compatibility minimize an effect of enantiostyly in promotion of outcrossing. Instead, it is proposed that style deflections may clear access of the pollinator to the anthers and protect female parts from injury by a vibrating heavy‐bodied visitor.
BREEDING SYSTEMS IN ASCLEPIAS INCARNATA L., A. SYRIACA L., AND A. VERTICILLATA L.
Authors: Kephart Susan R.
Published: January 2018

A series of experimental pollinations involving three sympatric species provided strong evidence for physiological and/or genetic barriers to hybridization in Asclepias. Pollen tubes were observed to penetrate the style in some interspecific crosses of all species pairs. Aniline blue fluorescence microscopy also demonstrated pollen tube penetration of foreign ovules following pollinations between A. incarnata and A. verticillata. However, none of the 279 total pollinations attempted between species yielded mature seed, indicating the presence of late pre‐fertilization or early post‐fertilization incompatibility. Intraspecific pollinations in greenhouse and field populations revealed greater crossability between populations than within populations of a single species. Self‐pollinations of A. verticillata were unsuccessful, while 29% and 4% of those of A. incarnata and A. syriaca, respectively, yielded mature follicles. It is suggested that the potential for autogamy, combined with floral mechanisms requiring pollination by insects, insure the advantages of both the genetic variability promoted by outcrossing and the reproductive assurance of uniparental reproduction. Strong reproductive barriers between species reduce the change of intergradation where species occur sympatrically.
STARCH GRANULE FORMATION IN DEVELOPING SEEDS OF PISUM SATIVUM L.: EFFECT OF GENOTYPE
Authors: Boyer C. D.
Published: January 2018

Cell development and starch granule formation in seeds of three pea (Pisum sativum L.) genotypes, R/R Rb/Rb, r/r Rb/Rb, and R/R rb/rb, affecting cotyledon starch were compared. Cotyledon cells at 10 days after flowering were highly vacuolated and contained small protein bodies in the vacuoles and small oval starch granules in the cytoplasm in all three genotypes. Gradients of cell development from the center to the periphery of the cotyledon and toward the cotyledon‐hypocotyl axis persisted through the cell enlargement, reserve synthesis, and into the maturation stages of cotyledon development. By 14 days after flowering, many small vacuoles lined with protein deposits had been formed. Vacuoles were only observed in peripheral and basal cells by 18 days after flowering. Starch granules were oval and birefringent in all three genotypes at 10 days. Starch granules in R/R Rb/Rb and R/R rb/rb cotyledons expanded regularly remaining nearly oval and birefringent throughout development. In contrast, starch granules from r/r Rb/Rb cotyledons began to fragment by 14 days after flowering. This process began as a single fissure, followed by a second fissure usually at or near right angles. Finally, because of the fragmentation, the granules appeared compound, and only a portion of the granule was birefringent. All genotypes contained nearly equal volumes of liquid endosperm and embryo at 10 days after flowering. In addition, a layer of parenchyma tissue (ovular and/or endospermic) inside the seed coat was observed. Although, thin walled and poorly defined cytologically, the parenchyma cells contained large numbers of starch granules. These granules were a mixture of simple and compound types in all genotypes. By 18 days after flowering, the parenchyma tissue was reduced to a small layer of cell walls and all starch granules had been mobilized.
ULTRASTRUCTURE OF CONIDIOGENESIS IN SPHAEROSTILBE OCHRACEA
Authors: Glover Sue U. , Hanlin Richard T.
Published: January 2018

Conidium development inSphaerostilbe ochraceais phialogenous. Mature synnemata are cup‐shaped at the apex. The hyphal tips inside the apex are cut off by a septum to form elongated phialides that initially are not distinguishable from other hyphae. Numerous small vesicles aggregate in the tips of the incipient phialides, after which a second wall layer is deposited inside the original wall of the young phialides. As the conidium forms, the outer wall layer breaks, leaving a minute collarette at the apex of the phialide. Some wall material adheres to the first conidium as it matures. Subsequent conidia push out of the mouth of the phialide; as they do so they separate and are held together in a mucoid droplet. Conidia are one‐celled when formed but soon become two‐celled through formation of a median septum.
NICKEL UPTAKE BY CALIFORNIAN STREPTANTHUS AND CAULANTHUS WITH PARTICULAR REFERENCE TO THE HYPERACCUMULATOR S. POLYGALOIDES GRAY (BRASSICACEAE)
Authors: Reeves Roger D. , Brooks Robert R. , Macfarlane Roger M.
Published: January 2018

The nickel content of herbarium specimens of Californian Streptanthus and Caulanthus has been determined. Serpentine‐tolerant species had nickel values of 10–100 μg/g (dry mass) except in the case of S. polygaloides Gray which had nickel values in the range 3,300–14,800 μg/g (0.33%–1.48%). This is the first hyperaccumulator of nickel found in the Americas. It is suggested that the later classification of S. polygaloides as the monotypic Microsemia polygaloides (Gray) Greene may be justified if the nickel accumulation data are used to reinforce the existing marked morphological differences from other Streptanthus.
VASCULAR PATTERNS IN STEMS OF ARACEAE: SUBFAMILY POTHOIDEAE
Authors: French J. C. , Tomlinson P. B.
Published: January 2018

The stem vasculature of representative species of ten of the 11 genera in the Pothoideae was analyzed with the aid of films of series of transverse sections. In all species a leaf trace typically diverges from a continuing axial bundle before departing to a leaf, with the possible exception of Heteropsis. However, within this common organizational scheme a considerable range of variation exists, e.g., with respect to degree of branching of axial bundles, and distance from a leaf‐trace branch to the point of leaf‐trace departure to a leaf. In addition, we have found a wide variety of patterns of bud‐trace organization in different genera of the Pothoideae. For example, prominent arcs composed of numerous bud traces occur in the central cylinder of Pothos, Pothoidium, and Heteropsis. Comparative anatomy leads to the conclusion that Pothos and Pothoidium more closely resemble Heteropsis than Anadendrum. Anadendrum should be dissociated from the tribe Pothoeae. With respect to other genera in the Pothoideae, our preliminary results suggest that each of the genera Anthurium, Culcasia, Zamioculcas, Acorus, and Gymnostuchys are highly distinct from each other.
STOMATA ON SEEDS AND FRUITS OF BAUHINIA (LEGUMINOSAE: CAESALPINIOIDEAE)
Authors: Rugenstein Seanna R. , Lersten Nels R.
Published: January 2018

Seeds of 45 species of Bauhinia (Leguminosae: Caesalpinioideae) were studied by scanning electron microscopy. Seeds of eight species have stomata which are mostly normal in appearance but lack subsidiary cells and are slightly recessed. Varying degrees of distortion or obscuring cuticular deposits were found in some species. This is the first unambiguous report of stomata on seeds of Leguminosae. Fruits of two of the eight species were also examined. Raised stomata with conspicuous subsidiary cells were found only on the outer pericarp surface.
FINE STRUCTURE OF MISTLETOE POLLEN. IV. EURASIAN AND AUSTRALIAN VISCUM L. (VISCACEAE)
Authors: Feuer Sylvia M. , Kuijt Job
Published: January 2018

Fifteen Eurasian and Australian species of Viscum L. were examined by light, scanning, and transmission electron microscopy. Pollen characters divide the species into two groups, each correlated with differences in habit and inflorescence structure: Group I (12 spp.) characterized by psilate or slightly sculptured exines and a non‐uniform ektexine pattern and Group II (3 spp.) possessing highly sculptured (echinate, rodlet) surfaces and uniform ektexine patterns. Within each of the groups, pollen characters divide the species into several subgroups. Among Group I, species V. nepalense, V. heyneanum and V. ovalifolium are particularly close. The Group I species, V. trilobatum, is placed in its own subgroup primarily because of its uniform ektexine pattern—a unique feature among Asian and Australian Viscum. Of the three Group II species, V. album and V. alniformosanae are palynologically almost indistinguishable. Pollen of the Group II V. cruciatum, though exomorphologically similar to V. album, is closest ultrastructurally to the Indian V. trilobatum. Overall, the most common and probably basic pollen characters among the Eurasian and Australian species include: subprolate, rounded convex almost spherical shapes; tricolporate apertures, and non‐uniform sculpturing and ektexine patterns. Oblate‐spheroidal or prolate‐spheroidal shapes, prominent sculpturing, and a uniform ektexine pattern are derived characters largely restricted to the Eurasian and Asian Group II species (V. album, V. alniformosanae, V. cruciatum).
PTEROCARYOID FRUITS (JUGLANDACEAE) IN THE PALEOGENE OF NORTH AMERICA AND THEIR EVOLUTIONARY AND BIOGEOGRAPHIC SIGNIFICANCE
Authors: Manchester Steven R. , Dilcher David L.
Published: January 2018

The Juglandaceae (walnut family) has an excellent fossil record of various organs extending back to the earliest Tertiary. Several genera which today are restricted to isolated geographic regions were widespread in the Northern Hemisphere during the Tertiary. This paper focuses upon the fossil record of thePterocaryaalliance of the subfamily Juglandoideae, tribe Juglandeae. ThePterocaryaalliance includes only two modern genera,Pterocarya(five species) andCyclocarya(one species), both restricted to Eurasia. Paleogene sediments of the Rocky Mountain Region have yielded three genera and four species referable to thePterocaryaalliance:Cyclocarya(two species),Pterocarya, and a new genus,Polyptera.Although three of the four Paleogene species described here are attributed to present day genera, each represents an extinct form, which cannot be accommodated by any single living species. These fossils, reviewed with other published reports, indicate that thePterocaryaalliance, like theEngelhardiaalliance of the same family, was more diverse and much more widespread geographically in the Tertiary than it is today.
ZINC‐TOLERANT ECOTYPES IN MELILOTUS ALBA (LEGUMINOSAE)
Authors: Miller Robert M.
Published: January 2018

Melilotus alba (Leguminosae) populations from mine sites in southwestern Wisconsin were shown to be ecotypically adapted to high levels of zinc in the soil. In greenhouse experiments using high‐zinc soil and high levels of zinc in sand culture, seedlings from mine populations grew better and suffered less mortality than did seedlings from roadside populations.
TISSUE RESPONSE TO PALLADIUM MICROPROBE, AS OBSERVED IN GOSSYPIUM HIRSUTUM L. (MALVACEAE)
Authors: Rugenstein Seanna R.
Published: January 2018

Small (250 μm diam) palladium microprobes, either sharpened or blunt‐tipped, were inserted into peduncles and petioles of field‐grown cotton (Gossypium hirsutum L. cv. ‘Deltapine 61‘). Two weeks after microprobe insertion, tissue was harvested and processed for subsequent light‐microscopic examination. Factors which influence structure and organization of wound response tissue, such as developmental stage of tissue at microprobe implantation site, are discussed. Patterns of differentiation in the wound response tissue which surrounds the microprobes are illustrated. There appeared to be direct rather than peripheral continuity between normal vascular tissue and vascular tissue formed within the wound callus surrounding microprobes implanted in petiole and peduncle. Apparently restoration of direct vascular connections between the original vascular tissue and the vascular tissue formed within the wound callus is a characteristic wound‐healing response following microprobe implantation in cotton.
RHODOPHYCEAN PIT PLUGS: AN ULTRASTRUCTURAL SURVEY WITH TAXONOMIC IMPLICATIONS
Authors: Pueschel Curt M. , Cole Kathleen M.
Published: January 2018

The fine structure of pit plugs was examined in 63 species of red algae representing 34 families. The number of plug cap layers was found to be a taxonomically reliable character when tested against a recent revision of the Rhodymeniales which established the order Palmariales. In a broader survey involving all the orders of red algae possessing pit plugs, three basic plug cap configurations were detected. These differ in having one, two, or no plug cap layers. Some taxa have plug caps in which the outer cap layer is greatly elaborated, however, this layer was shown to be positionally and cytochemically identical, thus probably homologous, to the outer cap layer of the typical two‐layered plug cap. The pit plug character confirms the validity of the order Palmariales and indicates that the Nemaliales and Cryptonemiales are heterogeneous assemblages. Revision of these groups along lines indicated by the plug character is supported by significant features of morphology and reproduction. These correlations lead us to propose thatRhodophysemaandCoriophyllumbe transferred to the Palmariales, that the Gelidiales be resurrected, that the Bonnemaisoniales (including the Naccariaceae) is deserving of recognition, that the Batrachospermaceae be raised to a higher rank which will also receive the Lemaneaceae and the Thoreaceae, and that the Corallinaceae and Hildenbrandiaceae both be raised to ordinal status.
STUDIES OF PALEOZOIC MARATTIALEANS: AN EARLY PENNSYLVANIAN SPECIES OF THE FERTILE FERN SCOLECOPTERIS
Authors: MILLAY M. A.
Published: January 2018

Remains of the fossil Marattiales are very rare in Lower Pennsylvanian sediments. The present report describes a new species of the fertile fern foliage Scolecopteris from the Lewis Creek, Kentucky locality (Lower or lower Middle Pennsylvanian). Scolecopteris conicaulis n. sp. has radial synangia composed of a ring of 4–7 elongate, exannulate sporangia. Most features of the synangia of S. conicaulis were previously hypothesized to be primitive in Scolecopteris based on geologically younger species. Supposed primitive characters include the large synangium pedicel with fiber core, an outer‐facing sporangial wall lacking differentiation or zonation, and large spores. The anatomy of the sporangium walls, pinnule morphology, and general spore type support an association with the Minor group of Scolecopteris. The new species is similar in several important features to Scolecopteris (Cyathotrachus) altus, the only other anatomically preserved fertile marattialean known from this early time, and indicates a considerably earlier origin for fertile foliage of this type.
BIOMASS AND PRODUCTION OF PONTEDERIA CORDATA AND POTAMOGETON EPIHYDRUS IN THREE CONNECTICUT RIVERS
Authors: Heisey Rod M. , Damman Antoni W. H.
Published: January 2018

Above‐ and below‐ground biomass of the emergent Pontederia cordata and the floating‐leaved Potamogeton epihydrus was measured during the growing season in three interconnected rivers in Connecticut, U.S.A. Maximum biomass of Pontederia, averaging 1,212 g m‐2 dry weight (524 g m‐2 above‐ground, 688 g m‐2 below‐ground), occurred 100–150 days after major spring growth began. Peak biomass of Potamogeton averaged 94 g m‐2 (81 g m‐2 above‐ground, 14 g m‐2 below‐ground) and was attained in 45–85 days. New growth of Pontederia in spring arose from, and was heavily subsidized by, the large biomass of living overwintered rhizomes and roots, which averaged 497 g m‐2 in early June. This new growth appeared to have been produced in only one season, but in reality it contained energy fixed the current season, plus energy carried over from previous years. Net production of Pontederia calculated for only one growing season averaged 1,049 g m‐2. Potamogeton also perennated from rhizomes, but the biomass of these organs in spring was low, averaging 11 g m‐2 in late May. Biomass of Potamogeton in summer consisted primarily of tissue produced during the current season. Rhizomes and roots comprised a much greater proportion of the plant in Pontederia than in Potamogeton. The ratio of new living below‐ground/above‐ground biomass of Pontederia rose from zero in spring to an average of 1.71 in autumn. For Potamogeton, the below‐ground/above‐ground ratio averaged 0.37 in late spring, 0.20 in midsummer, and 0.41 in autumn. The overwintered below‐ground biomass of Pontederia alive in spring was 42–79% of the new living below‐ground biomass the previous autumn. Net photosynthetic efficiency during the period between initiation of major growth in spring and attainment of peak biomass averaged 1.3% for Pontederia and 0.3% for Potamogeton.
SPECIAL PAPER: HAPLOIDS FROM POLLEN GRAINS—RETROSPECT AND PROSPECT
Authors: Maheshwari S. C. , Rashid A. , Tyagi A. K.
Published: January 2018

The production of large numbers of haploid plants from pollen grains in aseptic culture of anthers or isolated pollen grains has now been demonstrated in many angiosperms. It is a technique which holds much promise for creating desired variability by mutations for biochemical and applied genetics and for producing pure lines for crop improvement. This paper reviews the research on the production of haploids from pollen grains. The response is dependent on a variety of factors such as media formulation (especially the hormone component), genotype and physiological status of the donor plant, developmental stage of the pollen grain, anther culture environment and anther wall itself—all of which influence greatly the successful production of haploid plants. Although still in its infancy, the culture of isolated pollen is seen as a promising line of further research as it has the potential of offering several advantages over the culture of whole anthers.