bluuebunny/crossref_metadata_2025 huggingface dataset:
STIGMARIAN PETRIFACTIONS FROM THE PENNSYLVANIAN OF COLORADO
Authors: Jennings James R.
Published: January 2018

The designation Stigmaria ficoides is restricted to casts and impressions. Petrifactions of Stigmaria arnoldii sp. n. occur in Pennsylvanian age strata in Trout Creek Pass, Colorado. The rootlet gaps of this species appear narrow and elongate in both cross and longitudinal sections. Rootlet traces are contiguous with the secondary xylem to its outer margin and are surrounded by a small parenchyma sheath in the middle cortex. The outer cortex consists of an inner layer of primary tissue and a relatively thick zone of periderm. S. arnoldii most closely resembles material described as S. ficoides from England. Various stigmarian characters are evaluated with regard to their systematic or ontogenetic significance.
PHOTOPERIOD INDUCED CHANGE IN PHYLLOTAXIS IN XANTHIUM
Authors: Erickson Ralph O. , Meicenheimer Roger D.
Published: January 2018

Photoperiodic floral induction in Xanthium, achieved by subjecting the plants to two long nights, is accompanied by a transient change of the phyllotaxis from the (2, 3) contact parastichy pattern of vegetative plants, to a (3, 5) pattern during the transition. To specify the phyllotaxis, two parameters were estimated from transverse sections of apical buds of control and treated plants: the divergence angle, α, and the plastochron ratio, a. The plastochron ratio decreased progressively during transition from the vegetative to the reproductive state of growth, from a = 1.48 initially to a = 1.15 six days after the beginning of induction. The divergence angle was not altered during the transition. This change in phyllotaxis is interpreted as a change in the relative positioning of leaf primordia on the transitional apex. This transient change appears to be identical with the previously described long‐term change of the phyllotaxis of Xanthium brought about by treatment of plants with gibberellic acid.
OBSERVATIONS ON CHYTRIDIACEOUS PARASITES OF PHANEROGAMS. XXVII. A FURTHER STUDY OF PHYSODERMA HYDROCOTYLIDIS VIÉGAS AND TEIXEIRA
Authors: Sparrow Frederick K.
Published: January 2018

A further study of Physoderma hydrocotylidis from California on its host Hydrocotyle ranunculoides gives further details on its structure and development. EM micrographs reveal that the notably thin wall of the resting spore consists of an outer, an intermediate, and an inner layer. The complete wall thickness from measurements of these EM preparations is only 0.5 μm, the thinnest of any known Physoderma resting spore. Such resting spores germinate readily in 2–5 h by the dehiscence of a broad cap and formation of a protruding endosporganium. Zoospores from the latter infect epidermal host cells and produce either the endobiotic, polycentric rhizoidal system with tenuous filaments, turbinate cells and eventually resting spores, or a hitherto unknown epibiotic, monocentric, rhizidiaceous sporangial stage. Zoospores from the latter may all bear colorless lipid globules or all faintly orange‐colored ones.
MORPHOGENESIS OF CAPITATE GLANDULAR HAIRS OF CANNABIS SATIVA (CANNABACEAE)
Authors: Hammond Charles T. , Mahlberg Paul G.
Published: January 2018

The glandular secretory system in Cannabis sativa L. (marihuana) consists of three types of capitate glandular hairs (termed bulbous, capitate‐sessile, and capitate‐stalked) distinguishable by their morphology, development, and physiology. These gland types occur together in greatest abundance and developmental complexity on the abaxial surface of bracts which ensheath the developing ovary. Bulbous and capitate‐sessile glands are initiated on very young bract primordia and attain maturity during early stages of bract growth. Capitate‐stalked glands are initiated later in bract growth and undergo development and maturation on medium, to full sized bracts. Glands are epidermal in origin and derived, with one exception, from a single epidermal initial. The capitate‐stalked gland is the exception and is of special interest because it possesses a multicellular stalk secondarily derived from surrounding epidermal and subepidermal cells. Glands differentiate early in development into an upper secretory portion and a subtending auxiliary portion. The secretory portion, depending on gland type, may range from a few cells to a large, flattened multicellular disc of secretory cells. The secretory portion produces a membrane‐bound resinous product which caps the secretory cells. Capitate‐stalked glands are considered to be of particular evolutionary significance because they may represent a gland type secondarily derived from existing capitate‐sessile glands.
CHANGES IN PLASTID AND MITOCHONDRION CONTENT DURING MATURATION OF GENERATIVE CELLS OF SOLANUM (SOLANACEAE)
Authors: Clauhs Ronald P. , Grun Paul
Published: January 2018

A study was made of the number of plastids and mitochondria present in generative cells of Solanum immediately after microspore mitosis, and the fate of these organelles during development of the pollen was determined. Changes were followed via electron microscopy of anthers of S. chacoense and S. tuberosum Group Phureja × S. chacoense. In earliest stages the generative cells were oval and had one surface along the intine and other surfaces in contact with the vegetative cell. As the pollen matured the generative cells elongated, became spindle‐shaped, and were completely engulfed in the vegetative cells. At the earliest stages studied, both mitochondria and plastids were present in the generative cell. Plastids of the generative cell were, in contrast to those of the vegetative cells, fewer, smaller, and lacking in starch. Through the maturation stages the content of these organelles in the vegetative cells remained unchanged. While the generative cells retained mitochondria until anthesis, their plastids disappeared completely during maturation. This selective loss during generative cell maturation could lead to transmission of those characteristics encoded in plastid DNA through the pistillate parent only. The mechanism could explain earlier genetic evidence that plastid characters of Solanum were transmitted uniparentally.
SIEVE‐ELEMENT ONTOGENY IN THE ROOT OF EQUISETUM HYEMALE
Authors: Dute Roland R. , Evert Ray F.
Published: January 2018

Roots of Equisetum hyemale L. var. affine (Engelm.) A. A. Eat. were fixed in glutaraldehyde, postfixed in osmium tetroxide, and sieve elements of various ages were examined with the electron microscope. Young sieve elements are distinguished by their position within the vascular cylinder and by the presence of numerous refractive spherules, which originate within dilated portions of the endoplasmic reticulum (ER). Early in development, the sieve‐element walls undergo a substantial increase in thickness. This is followed by the appearance of massive ER aggregates in the cytoplasm and then by a phase involving stacking and sequestering of the remaining ER. Nuclear degeneration is initiated shortly after the appearance of the ER aggregates. The chromatin condenses into masses of variable size along the inner surface of the nuclear envelope. The envelope then ruptures and chromatin is released into the cytoplasm. During the period of nuclear degeneration, mitochondria and plastids undergo structural modification, while components such as dictyosomes, microtubules, and ribosomes degenerate and disappear. The remaining cytoplasmic components assume a parietal position in the cell, leaving the lumen of the cell clear in appearance. At maturity, the plasmalemma‐lined sieve element contains plastids, mitochondria, some ER, and refractive spherules. At this time many of the refractive spherules are discharged into the region of the wall. Pores between sieve elements occur largely on the end walls. During pore development, tubules of ER apparently traverse the pores, but because of the presence of massive callose deposits in the material examined, the true condition of mature pores could not be determined. The connections between mature sieve elements and pericycle cells are characterized by the presence of massive wall thickenings on the pericycle‐cell side. Plasmodesmata in the wall thickening are matched by pores on the sieve‐element side. Ontogenetic and cytoplasmic factors argue against use of the term “companion cell” for the vascular parenchyma cells associated with the sieve elements.
EXPERIMENTAL HYBRIDS IN EPILOBIUM (INCLUDING SECT. ZAUSCHNERIA) SPECIES WITH N = 15 (ONAGRACEAE)
Authors: Seavey Steven R. , Raven Peter H.
Published: January 2018

Experimental hybrids involving the three diploid subspecies of Epilobium sect. Zauschneria formed 15 bivalents at meiotic metaphase I, as did experimental hybrids between the three other species of Epilobium (comprising sect. Cordylophorum) with n = 15. The gametic chromosome number of E. suffruticosum Nutt., n = 15, and its relationship to the other two species are reported for the first time. Although we have not obtained hybrids between the species of these two sections, their morphological similarities are impressive and they are surely closely related.
PROTONEMAL ORGANIZATION AND GROWTH IN THE MOSS DAWSONIA SUPERBA: ULTRASTRUCTURAL CHARACTERISTICS
Authors: DeMaggio A. E. , Stetler D. A.
Published: January 2018

The elongating, tip cell of the protonema of Dawsonia superba is characterized by a variety of organelles distributed uniformly over the length of the cell. Chloroplasts, vacuoles, mitochondria and dictyosomes are present in the terminal portion of the cell. Dictyosomes are abundant throughout the cell and their production of vesicles is pronounced. Stratification of the cytoplasm and exclusion of organelles from the tip are not observed. The orientation of microtubules and microfibrils follows the pattern observed in filamentous fern prothallia. Microtubules are not observed at the tip of the protonema, but microfibrils are abundant and randomly oriented. While microtubules and microfibrils in lower regions of the apical dome are arranged randomly, more basally they assume an axial arrangement.
NUCLEAR DNA CONTENT OF EMBRYONIC RADICLES AND CULTURED STATIONARY PHASE ROOT TIPS OF PEA (PISUM SATIVUM L.)
Authors: Jones Philip A.
Published: January 2018

Cells in mature embryos and stationary phase (SP) root meristems of pea arrest in G1 and G2 of the cell cycle. The patterns of distribution of G2 nuclei in radicles and SP meristems, with and without G2 factor, were compared by using cytophotometric analysis of the relative amount of DNA/nucleus in sectioned material. Radicles and SP meristems were each divided into 5 zones and the ratio of G1 to G2 nuclei was determined for each zone. The G2 population in the radicle is restricted mainly to the embryonic cortex. A small part of the G2 population was located in the central cylinder and the root cap. In SP meristems without G2 factor, the pattern of distribution of G2 cells was similar to that in radicles. SP meristems with G2 factor contained G2 arrested nuclei in all regions of the root tip. In each region the percentage of G2 nuclei was higher than that in the same region of SP meristems without G2 factor. This indicates that the population of cells that responds to G2 factor is distributed throughout the root tip.
THE INFLUENCE AND COMPARISON OF INDIVIDUAL FOREST TREES ON SOIL PROPERTIES AND POSSIBLE INHIBITION OF NITRIFICATION DUE TO INTACT VEGETATION
Authors: Lodhi M. A. K.
Published: January 2018

Soil properties were found to vary with increasing distance from tree trunks of individuals of the same species, and different species were found to vary in their effects on soil properties. The differences in pH and mineral concentration at different distances from the trunk were often statistically significant even under the same tree. When all species are considered, iron had the least variability at different distances from the trunks of all minerals investigated, followed by potassium. Nitrate nitrogen had the greatest overall variability at different distances from the trunks. Ammonium nitrogen in the soil was always considerably higher than nitrate nitrogen when compared at each distance from the trunk under each species. Low amounts of nitrate nitrogen could not have been due to its uptake by the intact vegetation, because the soil samples were taken before the active growth period. It seems possible that the variable tree litter under different species plays an important role in controlling the soil pH, nitrification, and mineralization. Thus, it appears that in a climax community different dominating species, by developing variable physio‐ecological niches, can determine the variable undergrowth vegetation under them.
DIURNAL VARIATION IN THE VOLATILE TERPENOIDS OF JUNIPERUS SCOPULORUM (CUPRESSACEAE)
Authors: Adams Robert P. , Hagerman Ann
Published: January 2018

The volatile oils of four trees of Juniperus scopulorum were examined at 9 am, 12 noon, 3 pm, 6 pm, 10 pm, 2 am, and 6 am on consecutive days with a temperature range of 64 F and 88.5 F daily. Three‐way analysis of variance of 37 compounds revealed 36 with significant differences among trees, 11 with significant differences between days, 13 compounds with significant diurnal variation and 9 compounds which showed some significant interaction term differences. Most of the variation occurred among trees. Oxygenated terpenes and sesquiterpenes tended to increase during the day while sabinene decreased until late evening and increased during the early morning. Correlations with temperature appeared to lag and did not match the pattern in three species of Juniperus reported by other investigators. The effect of diurnal variations on chemosystematic classifications was estimated by using numerical taxonomy and principal coordinate analysis. Diurnal effects were not found to be important sources of error for chemosystematics in J. scopulorum if character weighting were used to maximize the genotype differences. However, this may not be true for work involving population sampling of other species over large regions.
AMYLASE POLYMORPHISM IN CITRUS AND SOME RELATED GENERA
Authors: Esen Asim , Scora Rainer W.
Published: January 2018

Amylase polymorphism was studied by electrophoresing crude protein extracts from mature leaves of Citrus and some related genera in polyacrylamide gel slabs. A total of 25 isoenzymes distributed within 2 distinct zones were resolved. Cultivars of C. medica were the least polymorphic with 5 isoenzymes, those of C. paradisi were the most polymorphic with 14 isoenzymes; the other taxa were between these two extremes. Cultivars within species, in general, had no qualitative differences in their isoenzymes profiles with the exception of C. aurantifolia, C. limon, and C. aurantium. Certain isoenzymes showed quantitative differences among taxa. Data provided evidence substantiating the presumed hybrid origin of some taxa. The potential of isoenzyme profiles in taxonomic and genetic studies was discussed.
THE LATERAL MERISTEM AND ITS DERIVATIVES IN THE CORM OF ISOETES MURICATA
Authors: Kruatrachue Maleeya , Evert Ray F.
Published: January 2018

Corm tissue of Isoetes muricata Dur. was fixed in glutaraldehyde and postfixed in osmium tetroxide for electron microscopy. Very young secondary sieve elements can be distinguished from contiguous cambial cells by their distinctive plastids and by the presence of crystalline and/or fibrillar proteinaceous material in dilated cisternae of rough endoplasmic reticulum (ER). At maturity, the sieve elements are lined by the plasmalemma and a parietal, anastomosing network of smooth ER. Degenerate nuclei persist in all mature sieve elements. In addition, mature sieve elments contain plastids and mitochondria. Sieve‐area pores are present in all walls. The lateral meristem of I. muricata consists of 2–3 layers of cells year‐round. Judging from numerous collections made between October 1972 and July 1975, new sieve‐element differentiation precedes cambial activity by about a month. Early in May, 1–2 cells immediately adjacent to already mature sieve elements differentiate directly into sieve elements without prior division. In early June, at about the time sieve‐element differentiation is completed, cambial division begins. Division is sporadic, not uniform throughout the meristem. Dormancy callose accumulates in the secondary sieve elements in late October, and is removed in early May, at about the same time new sieve‐element differentiation begins. Cells of the dormant cambium are characterized by the presence of numerous small vacuoles and large quantities of storage materials, including lipid droplets, starch grains, and tannin. By contrast, active cambial cells contain few large vacuoles with little or no tannin, and they have little storage material.
ENZYME POLYMORPHISMS AS GENETIC MARKERS IN THE AVOCADO
Authors: Torres Andrew M. , Diedenhofen Ulrike , Bergh B. O. , Knight Robert J.
Published: January 2018

Cultivated varieties (cvs) of the avocado (Persea americana) originate by selfing, hybridization or chance selections, and are then propagated by grafting. The mesocarps of a given cv are consequently all genetically identical. Mesocarp gene‐enzyme systems were examined by starch gel electrophoresis and were found to be highly polymorphic. Alcohol dehydrogenase, phosphoglucomutase, glutamic‐oxaloacetic transaminase and leucine aminopeptidase are coded by 10 genes with 20 condominant alleles. ‘Seedling’ populations have been produced by selfing or by hybridizing cvs. Seedlings were found to segregate in normal Mendelian fashion for any gene for which the parent or parents were heterozygous. No isozyme evidence contradicted the reported parentage of several cvs of hybrid or selfed origin. Outcrossing, as indicated by the presence of a non‐parental isozyme, was detected among the seedlings of a supposed selfed population. To our knowledge, this is the first report of molecular genetics and of the genetics of any single‐gene character for the avocado. Possible applications are discussed.
AN INVESTIGATION OF THE MORPHOGENETIC MECHANISMS WHICH CONTROL THE DEVELOPMENT OF ZONATION IN SEEDLING SHOOT APICAL MERISTEMS
Authors: Mauseth James D.
Published: January 2018

The development of zonation in the shoot apical meristems of 28 species of cacti was examined. At germination the embryonic apex may have one of three types of organization: 1) tunica/corpus; 2) tunica/central mother cells/corpus; 3) tunica/central mother cells/peripheral zone/pith‐rib meristem. Apices of the third type have complete zonation and undergo little or no further structural development. Both of the other types develop the missing zones. First, the apices become mitotically active, and peripheral zone characters develop in the outer corpus. Simultaneously, or slightly later, the central mother cells differentiate if they are not yet present. The final step is the formation of the pith‐rib meristem. The sequence of appearance of the zones was constant throughout all species examined, but the time of appearance of only one zone could be correlated with any other morphogenetic process: the development of peripheral zone characteristics in the outer corpus occurs with or before the beginning of leaf production. The development of zonation appears to be independent of apical size, shape, or age, either real age or plastochron age. This has been interpreted to indicate that the metabolic mechanism controlling the development of zonation in shoot apical meristems is largely autonomous and independent of other aspects of morphogenesis occurring in the seedling. Also, the fact that leaf initiation and shoot axis production can both occur before the development of either the central mother cells or the pith‐rib meristem indicates that neither of these zones is essential for these two apical morphogenetic activities.
A REAPPRAISAL OF THE SUBGENUS GLYCINE
Authors: Newell C. A. , Hymowitz T.
Published: January 2018

The genus Glycine Willd. is divided into three subgenera, Glycine Willd., Soja (Moench) F. J. Herm., and Bracteata Verdc. Six species are currently recognized in the subgenus Glycine: G. canescens F. J. Herm., G. clandestina Willd., G. falcata Benth., G. latrobeana (Meissn.) Benth., G. tabacina (Labill.) Benth., and G. tomentella Hayata. Distribution of the subgenus extends from south China to Tasmania and includes several Pacific islands. A collection of these species was examined cytologically and morphologically in an attempt to evaluate existing variability between and within taxa. Chromosome counts confirmed G. canescens, G. clandestina and G. falcata to be diploid with 2n = 40. Both tetraploids (2n = 80) and diploids were found in G. tabacina, the latter restricted to Australia. Glycine tomentella accessions were primarily tetraploid, but several collections from New South Wales, Australia, were found to be aneuploid with 78 chromosomes. One collection was aneuploid at the diploid level with 38 chromosomes. Meiosis appeared normal in the aneuploids with regular bivalent formation. Several accessions previously identified as G. tomentella were diploid. Seed of G. latrobeana was not available for analysis. Numerical techniques in the form of cluster analysis and principal components analysis were applied to morphological data on vegetative and inflorescence characters obtained from each collection. Numerical analysis grouped the accessions essentially according to current species delimitations with some exceptions. Glycine tabacina specimens from Taiwan approached G. clandestina in several characteristics. The diploid G. tomentella specimens formed a separate cluster and appeared morphologically distinct from the remaining taxa.
NUCLEAR DNA CONTENT IN POPULATIONS OF PINUS RIGIDA
Authors: Dhillon Sukhraj S. , Berlyn Graeme P. , Miksche Jerome P.
Published: January 2018

Five populations of Pinus rigida growing in contrasting ecological situations ranging from North Carolina (35°53'N latitude) to Quebec (45°06'N latitude) showed no significant variation in amounts of nuclear DNA with respect to germinating seedlings. Nuclear volume of dormant nuclei also showed no significant variation between and within populations, a finding that is consistent with the concept that the basic 2C DNA value of Pinus rigida is uniform under all habitats. This finding is in contrast to numerous reports for other coniferous species.
THERMAL SENSITIVITIES OF MALATE DEHYDROGENASE ISOZYMES IN TYPHA
Authors: Liu Edwin H. , Sharitz Rebecca R. , Smith Michael H.
Published: January 2018

Two species of cattail. Typha latifolia L. and T. domingensis Pers., occur naturally along the shoreline of Par Pond, an 1,128 ha impoundment subjected to intermittent thermal stress at the Savannah River Plant in South Carolina. T. domingensis is not tolerant of the stresses imposed at the hottest section of this lake. Typha latifolia is established throughout the lake but at the hottest section displays an altered morphology compared with stands from ambient areas. Both T. latifolia and T. domingensis are electrophoretically monomorphic, and no variation in isozyme expression in ten enzyme systems was recorded in populations from Par Pond. The malate dehydrogenase (MDH) isozyme patterns for T. latifolia and T. domingensis are identical, but their thermal sensitivities differ sharply. All six major T. domingensis MDH isozymes are denatured by heating at 50 C; whereas, T. latifolia has three isozymes which are stable at 50 C and three isozymes which are denatured at this temperature. Tests of thermal stability are more useful than measurements of electrophoretic mobility in detecting enzyme differences and a possible biochemical basis for differences in thermal tolerance in these natural populations.
CRUCIFORM NUCLEAR DIVISION IN SOROSPHAERA VERONICAE
Authors: Dylewski Daniel P. , Braselton James P. , Miller Charles E.
Published: January 2018

Sorosphaera veronicae Schroet. is an endobiotic, holocarpic, obligately parasitic fungus presently classified in the Plasmodiophoromycetes. The ultrastructure of nuclear envelope formation in somatic nuclear division in cystosoral plasmodia was studied. The inner membrane of the nuclear envelope during prophase appears to invaginate and blebb off intranuclear membranous vesicles. The intranuclear membranous vesicles become associated with the surface of the separating chromatin in anaphase and eventually are involved in the formation of daughter nuclear envelopes within the original nuclear envelope. The sequence of nuclear envelope breakdown and reformation in S. veronicae is noteworthy because it emphasizes alternate methods of nuclear envelope formation other than the generally considered “typical” formation described in Allium cepa L.
RATE OF PHOTOSYNTHESIS AND RESPIRATION IN DIFFERENT LICHEN TISSUES BY THE CARTESIAN DIVER TECHNIQUE
Authors: Pearson L. C. , Brammer Erik
Published: January 2018

The Cartesian diver technique has been used for measuring respiration in Protozoa, small crustaceans, insects, and in animal tissue; it can also be used to measure both respiration and photosynthesis in unicellular plants and in plant tissues. In two lichens, Peltigera canina and Evernia prunastri, algal‐containing tissues were more than 2½ times as active metabolically as medulla. In Peltigera, cortex was slightly more active, rhizines about equally active, and apothecia about a tenth as active as medulla. Light compensation point and peak rates of apparent photosynthesis were reached at higher light intensities in Evernia than in Peltigera. In both lichens, light seemed to retard respiration in the medulla.
POLLEN WALL AND APERTURE DEVELOPMENT IN HELIANTHUS ANNUUS (COMPOSITAE: HELIANTHEAE)
Authors: Horner Harry T. , Pearson Christine B.
Published: January 2018

Wall development of tricolpate pollen of sunflower was studied by light and by scanning and transmission electron microscopy. The wall and colpi are initiated during the tetrad stage, producing a young, spinulate, two‐layered exine (ektexine and endexine) separated by a “spacer layer.” After release from the tetrads, the individual microspores round up and enlarge. The exine layers increase in thickness and complexity from sporopollenin contributed by the tapetum and microspores. During the mid‐vacuolate microspore stage, the tapetum becomes plasmodial and surrounds the developing microspores. At the vacuolate pollen stage, after the wall and colpi are completely formed, the plasmodial tapetum breaks down and releases its contents into the locule. Some of the contents are presumably utilized by the pollen to make storage reserves while other components, such as lipids and proteins, fill the spaces within the pollen wall exine. Pollen wall ontogeny provides a scheme of terms for mature composite walls in general. The various events associated with microsporogenesis in sunflower are compared with those reported in other pertinent studies.
KINEMATICS OF HYPOCOTYL CURVATURE
Authors: Silk Wendy Kuhn , Erickson Ralph O.
Published: January 2018

Time lapse photographs were analyzed for curvature, κ, of the plumular hook as a function of distance from the apex, s, of seedlings of lettuce. Lactuca sativa cv ‘Grand Rapids,‘ during hook maintenance (red light) and hook opening (white light). Curvature of the inner edge of the photographic projection of the hook increases from 0.14 mm–1 near the apex to 12.7 mm–1 at the hook bisector (about 1 mm from the apex) and decreases to approximately zero below the hook (2 mm from the apex). Using concepts from fluid dynamics we relate growth rates to curvature changes. For a material element of stem cross section located at s we predict that

urn:x-wiley:00029122:ajb206072:equation:ajb206072-math-0001

where M(s,o) and M(s,i) are the relative elemental growth rates at the outer and inner edges of the hypocotyl cross section, w is element width, t is time, and u(s) is velocity of departure of s from the apex. During hook maintenance ∂[ln(1 + κw)]/∂t is approximately zero if the apex is taken as origin. As each hypocotyl element is displaced from the apex it becomes increasingly curved; then, after displacement past the hook bisector, the element straightens. Growth rates, determined by measurements of the displacement of epidermal hairs, show the pattern expected from the equation: On the apical side of the hook, relative growth rates of the outer edge exceed growth of the inner edge, M(s,o) > M(s,i), while on the basal side of the hook. M(s,o) < M(s,i). The constraint for hook maintenance is that [L(s,o) – L(s,i)] /u(s) be constant in time, where L(s,o) and L(s,i) are the relative elemental growth rates at s. During hook opening ∂[ln(1 + κw)]/∂t becomes important.
THE FOLIAR EPIDERMIS IN TILLANDSIOIDEAE (BROMELIACEAE) AND ITS ROLE IN HABITAT SELECTION
Authors: Benzing D. H. , Seemann J. , Renfrow A.
Published: January 2018

Structural features of the foliar epidermal surfaces of selected epiphytic members of subfamily Tillandsioideae of Bromeliaceae were examined to determine why xeromorphic nonimpounding (atmospheric) species with a dense layer of foliar trichomes are seldom found in deeply shaded humid portions of the forest profile, whereas tank‐forming members of the same subfamily often abound in such sites. Two features of the peltate trichome which appear to play a major role in enforcing habitat preferences among members of Tillandsioideae are (1) anatomical features of the walls of certain trichome cells which affect the mobility of the shield and. (2) variations in juxtaposition of trichomes and stomates on the leaf surface. Both features are involved in inhibition of gas exchange in wet leaves; trichome shield flexibility is also associated with high leaf reflectivity when the leaf surface is dry.
CHANGES IN WEIGHT, NITROGEN ACCUMULATION, RESPIRATION AND PHOTOSYNTHESIS DURING GROWTH AND DEVELOPMENT OF SEEDS AND PODS OF PHASEOLUS VULGARIS
Authors: Oliker M. , Poljakoff‐Mayber A. , Mayer A. M.
Published: January 2018

The growth and development of pods and seeds of Phaseolus vulgaris are described by the following parameters: fresh and dry weight, length, ratio of fresh weight to length and nitrogen content. Pod and seed development are independent and sequential. Pod photosynthesis contributes only marginally to pod development, but may be significant in refixing CO2 released in respiration. Pods and seeds do not seem to act simply as competing sinks. Nitrogen accumulation in the seeds begins only when it has ceased in the pods. Ways in which regulation may be achieved are discussed. Manipulation of nitrogen fertilization to enhance seed growth is suggested.
STUDIES IN THE BIGNONIACEAE. I. ONTOGENY OF DIMORPHIC ANTHER TAPETUM IN PYROSTEGIA
Authors: Gupta Shrish C. , Nanda Kanan
Published: January 2018

Development of the anther wall was studied with special reference to the tapetum in Pyrostegia ignea. The archesporium in each microsporangium is horseshoe‐shaped. The inner tapetum develops earlier from the vegetative cells of the connective region while the outer differentiates a little later from the parietal layers. Thus, the tapetum has a distinct dual origin. The two tapetal layers exhibit a pronounced structural dimorphism. Sometimes, sterile septae, partitioning the sporogenous tissue, develop in microsporangia. A prominent membrane with Ubisch granules (orbicules) is organised on the inner tangential surface of the tapetal protoplasts facing the uninucleate microspores.
THE STRUCTURE AND DEVELOPMENT OF AN UNUSUAL TYPE OF ARTICULATED LATICIFER IN MAMMILLARIA (CACTACEAE)
Authors: Mauseth James D.
Published: January 2018

Although the laticifers of several species of Mammillaria can technically be classified as being of the articulated type, they differ significantly from all other reported articulated laticifers. They are derived from cells which differentiate only in older tissues, never in meristematic or young regions. The development involves the complete lysis of masses of cells, not just the perforation or resorption of the end walls in a single file of cells. At maturity, the laticifer lumen is lined with a one‐to‐several layered epithelium which may be quite thick. The laticifers increase in diameter with age, apparently by the lysis of the inner epithelial cells. Laticifers occur in the pith, cortex and tubercles of the vegetative body but were not observed in the roots, flower parts or in seedlings up to eight months old. Seven species were studied, all of which have “milky sap.” and the laticifers of each were virtually identical to the laticifers of the others.
INFLUENCE OF IRRADIATION, SOIL WATER POTENTIAL, AND LEAF TEMPERATURE ON LEAF MORPHOLOGY OF A DESERT BROADLEAF, ENCELIA FARINOSA GRAY (COMPOSITAE)
Authors: Smith William K. , Nobel Park S.
Published: January 2018

Laboratory experiments were performed to evaluate observed seasonal changes in leaf morphology of the desert perennial shrub, Encelia farinosa Gray. Plants were grown under low or high conditions of photosynthetically active irradiation, soil water potential (Ψsoil), and leaf temperature (8 different experimental regimes). The relative growth rate, leaf water vapor conductance, leaf water potential, and leaf length were all greater for the high Ψsoil regimes, the largest leaves occurring at low irradiation. High irradiation during growth led to thicker leaves with a higher internal to external leaf area ratio (Ames/A); low Ψsoil tended to increase Ames/A somewhat. High irradiation also led to decreased absorptance to solar irradiation caused by increased pubescence. High leaf temperature during development resulted in slightly smaller, thicker leaves with higher Ames/A. Thus, irradiation appeared to have its major influence on leaf thickness, Ames/A, and absorptance, with a secondary effect on leaf length; Ψsoil affected primarily leaf length, growth rate, and water status, and secondarily Ames/A. Results are discussed with regard to recent ecophysiological studies on the observed seasonal changes in leaf morphology of E. farinosa.
CONTRIBUTION OF POLLEN MORPHOLOGY TO SYSTEMATICS OF COLLOMIA (POLEMONIACEAE)
Authors: Chuang Tsan‐Iang , Hsieh Winston C. , Wilken Dieter H.
Published: January 2018

Pollen morphology of 14 species of Collomia (Polemoniaceae) was examined by light microscopy, and by both scanning and transmission electron microscopy. Four distinct pollen types were observed which are based principally upon 1) shape, number and distribution of apertures, and 2) surface sculpturing: Type 1—zonocolporate with striate ridges; Type 2—zonocolporate with striato‐reticulate ridges; Type 3—pantoporate with radiate ridges; Type 4—pantoporate with irregularly reticulate ridges. Evaluation of pollen morphology reveals considerable discrepancy with respect to presently accepted sectional classification. Collomia grandiflora of sect. Collomia has a pollen type similar to that of members of sect. Collomiastrum and is now interpreted as representing an independent evolutionary line derived from the latter section. Collomia diversifolia of sect. Courtoisia has a pollen morphology similar to that of sect. Collomia. whereas C. heterophylla of the same section possesses pollen unique within the genus. This last pollen type shows close similarity to the pollen of members of Polemonium, Gilia, Leptodactylon, and Ipomopsis. Pollen of C. tinctoria and C. tracyi of sect. Collomia are anomalous within Polemoniaceae. No significant difference in exine stratification was discernible among the four pollen types.
ULTRASTRUCTURE OF OOSPORE GERMINATION IN PYTHIUM APHANIDERMATUM
Authors: Ruben D. M. , Stanghellini M. E.
Published: January 2018

Transmission electron microscopy was used in an examination of dormant and germinating oospores of Pythium aphanidermatum (Edson) Fitzp. Predominant cytoplasmic components of the dormant oospore were a single, centrally located globule and numerous storage bodies surrounding the globule. The lipid nature of the central globule and storage bodies was indicated by the examination of Br2‐treated and untreated, fixed specimens. Three layers of the oospore wall were distinguished. During the early stages of oospore germination, the central globule developed incurvatures and became partially surrounded by vacuoles. The thick middle layer of the wall showed a change in staining properties and became thin in the region of germ tube emergence. Germlings incubated on corn meal agar differed substantially from those incubated in nutrient broth during the later stages of germination. The role of vacuoles and vesicles in the utilization of storage reserves during germination is discussed.
GROWTH AND DIFFERENTIATION OF JUICE VESICLES OF ORANGE GROWN IN VITRO
Authors: Unger James W. , Feng Kuo Ao
Published: January 2018

Juice vesicles of Valencia orange were grown on agar bases containing different concentrations of kinetin plus mineral and organic constituents, or in comparable liquid solution (shake cultures), maintained at approximately 26 C. Shake cultures enlarge most rapidly, but both maintain similar patterns of anatomical development. Typically, marginal parenchymatous cells of the sac become meristematic and develop, largely by periclinal division, generalized cambial meristems that enlarge the callus by the addition of linear rows of cells. Chloroplasts and wound tracheids with bordered pits mature within 30 days, but to date no further differentiation has been noted. Surface cells frequently enlarge, detach, and grow into branched hyphal aggregations of cells. Media containing 1.0 mg/liter kinetin causes greater enlargement of callus than media with 0.02 mg/liter kinetin.
HOMOEOLOGOUS CHROMOSOME PAIRING AND RESTRICTED SEGREGATION IN THE FERN CERATOPTERIS
Authors: Hickok Leslie G.
Published: January 2018

The segregation of a marker characterized by pale green gametophytes was monitored within an inbreeding study of the polyploid fern Ceratopteris. Although all of the sporophytes showing segregation were derived from the self‐fertilization of haploid gametophytes, a low overall frequency of 2.5% pale gametophytes was observed in the F3–F5 generations. A model based upon a duplicated locus and homoeologous chromosome pairing can explain the segregational behavior within the study. The overall level of homoeologous pairing was determined to be 10%. Occasionally, green gametophytes that were presumably heterozygous for the marker contained pale sectors. This behavior may involve mitotic crossing‐over between homoeologous chromosomes.
DEVELOPMENT OF PLANTS FROM PROTOPLASTS OF SOLANUM (SOLANACEAE)
Authors: Grun Paul , Chu Liu‐Jen
Published: January 2018

Experiments were performed to determine conditions critical to the isolation and culture of protoplasts from leaf mesophyll cells of a Solanum Section Tuberarium diploid clone, a S. phureja × S. chacoense F1 hybrid. The optimum concentration of cellulase (Cellulysin) was 0.4%, while pectinase (Macerase) was inhibitory, even at a low concentration (0.075%). Maximum yields of protoplasts were achieved when the enzyme solution was not changed during incubation, and slow oscillation (60 rpm) on a shaker was used. When detached leaves were held under low light intensities or in the darkness for 3–5 days prior to protoplast production, results were more consistent than when the leaves were used directly from the greenhouse. Following dark or low light treatment the optimum osmolarity of the isolation and growth media was approximately 0.3–0.4 M. Of nine growth media tested only those of Nitsch and Ohyama and of Upadhya supported callus development, but the callus was often loose and did not differentiate roots or shoots. Callus from protoplasts cultured in the Upadhya medium modified by addition of glycine, vitamins, and casein hydrolysate, and subsequently transferred to the medium of Lam, formed roots and shoots when cultures were maintained in light. Mature plants were obtained following transfer to modified White's medium and later transplantation to soil.
EARLY LEAF ONTOGENY AND THE SHOOT APEX OF COLOPHOSPERMUM MOPANE (LEGUMINOSAE)
Authors: Stein Otto L.
Published: January 2018

Shoot tips of Colophospermum mopane (Kirk ex Benth.) Kirk ex Léonard produce leaves which at maturity are bifoliate and devoid of stipules. Investigation of their early ontogeny, however, shows that these leaves begin as trifoliate structures partially enclosed by their stipules. The latter are fused along their mid regions, forming a tongue‐like “connector.” The lower chamber of this stipule pair harbors the apical meristem while the upper compartment enfolds the two lateral leaflets. The terminal leaflet, histologically resembling the stipules, also fulfills a similar function by covering the top portion of its sister leaflets. Anatomically, the shoot apex displays a pendulum symmetry, with rather steep elevation of that internode portion which subtends the newly formed primordium. Some comparisons with the shoot apex of Hymenaea are drawn.
ULTRASTRUCTURAL ASPECTS OF TWO SPECIES OF GUTTULINOPSIS
Authors: Erdos Gregory W. , Raper Kenneth B.
Published: January 2018

Two acrasid cellular slime molds. Guttulinopsis vulgaris and G. nivea, are compared at the ultrastructural level. The amoebae of the two species are indistinguishable except for the presence of intranuclear fibers in G. vulgaris. Both species share some unusual features, including: plate‐like cristae in the mitochondria, production of microbody‐like organelles in the perinuclear space, spores with thin bilaminar walls, and stalks containing microfilaments bound in striated bundles. These and other observations are discussed with regard to the development of the sorocarps and the relationship of the genus to other members of the Acrasida.
THE FLAVONOIDS OF ONAGRACEAE, TRIBE EPILOBIEAE: EPILOBIUM SECT. EPILOBIUM
Authors: Averett John E. , Kerr Barbara J. , Raven Peter H.
Published: January 2018

An analysis of about 100 populations of 39 taxa of Epilobium sect. Epilobium showed quercetin 3‐0‐rhamnoside and glucoside and myricetin 3‐0‐rhamnoside and glucoside to be present in most species, with the arabinosides present in some and in much smaller quantities. Kaempferol 3‐0‐rhamnoside was also present in some populations of some entities in small quantities. Variability, particularly in the presence of myricetin 3‐0‐rhamnoside and quercetin 3‐0‐glucoside, was characteristic of some species, especially those of Australia and New Zealand.
ETAPTERIS LECLERCQII SP. N., A ZYGOPTERID FERN FROM THE PENNSYLVANIAN OF NORTH AMERICA
Authors: Smoot Edith L. , Taylor Thomas N.
Published: January 2018

The zygopterid fern Etapteris leclercqii sp. n. is described from Lower Pennsylvanian age coal balls from the Lewis Creek, Kentucky, locality. Isolated petioles extend up to 15.0 cm in length and 5.0 mm in diam; no lateral axes have been observed. The clepsydroid‐shaped petiole trace is characterized by lateral arms that sharply taper and by the production of peripheral loops prior to the separation of pinna traces from the stele. Large irregularly shaped multicellular hairs are randomly scattered over the surface of the petioles. When compared with other currently recognized zygopterid ferns, E. leclercqii appears most similar to Metaclepsydropsis duplex. Based on the configuration of the leaf trace and the occurrence of peripheral loops, it is suggested that E. leclercqii may represent the most primitive species of the genus known to date.
STUDIES OF PALEOZOIC MARATTIALEANS: THE MORPHOLOGY AND PHYLOGENETIC POSITION OF EOANGIOPTERIS GOODII SP. N.
Authors: Millay Michael A.
Published: January 2018

Eoangiopteris goodii sp. n. is described from Upper Pennsylvanian coal balls from Ohio (Shade locality) containing isolated pecopterid pinnules approx. 7 × 9 mm that bear up to 20 linear synangia on the lower surface. The synangia extend at right angles from the midrib to the downturned pinnule margins and measure 2.0–3.5 mm in length. Individual synangia are compact and are composed of 10–19 sporangia that have their bases embedded in an elongate parenchymatous pad. In longitudinal section sporangia measure 0.4 × 2.0 mm and have acute elongate, curved apices. Spores average 70 μm in diam and are most similar to the dispersed spore genus Verrucosisporites. Eoangiopteris goodii differs from the generitype E. andrewsii Mamay in its greater size, pinnule histology, and spore type. Sporangium wall complexity and spore type of the two presently known species of Eoangiopteris are considered to be at about the same evolutionary level as the more primitive species of Scolecopteris. Construction of the synangia in Eoangiopteris is different from that of Scolecopteris and indicates that at least two evolutionary lines are recognizable within the Pennsylvanian Marattiales.
CHROMOSOMES OF CORSIA (CORSIACEAE)
Authors: Kores Paul , White David A. , Thien Leonard B.
Published: January 2018

A chromosome number of 2n = 18 is reported for Corsia cornuta (plus karyotype) and Corsia clypeata of the Corsiaceae from Papua New Guinea.
THE DEVELOPMENT OF THE SPOROCARP OF MARSILEA VESTITA
Authors: Bilderback D. E.
Published: January 2018

The tissues of the sporocarp of Marsilea vestita undergo profound changes during development. Early in development, the cells of the peripheral tissues, epidermis, hypodermis and layers of the transitional zone between the hypodermis and more internal tissues contain prominent vacuolar bodies. As development proceeds, these vacuolar bodies disappear. Prominent amyloplasts are found only in the guard cells and in the cells of the transitional zone. Later in development the cells of the hypodermis divide periclinally forming two layers which differentiate as macrosclereids. The cells of the outermost layer of the transitional zone differentiate as osteosclereids. Internally, the cells of the sorophore accumulate large amounts of mucilage in the central vacuoles. The peripheral cytoplasm ultimately degenerates leaving just hygroscopic mucilage. The mucilage carbohydrate contains the sugars, rhamnose and arabinose. In the young sorus, only the spore mother cells and the cells of the indusium contain amyloplasts. By the time of meiosis, there is a massive accumulation of starch in the receptacle, stalk and jacket but not in the tapetum of the sporangia. Late in development, the starch disappears and the mega‐ and microspores become coated with carbohydrate.
ON PHENOTYPIC EXPRESSION, MORPHOGENETIC PATTERN AND SYNANGIUM EVOLUTION IN PSILOTUM
Authors: Rouffa Albert S.
Published: January 2018

Both the typical form and the appendageless variant of Psilotum nudum produce terminal synangia at the ultimate tips of the aerial axes. One clone in particular of the typical appendaged form produced synangia entirely at the tips of the aerial branches, as in the appendageless variant, and also developed occasional lateral transitional entities on the upper aerial axis displaying appendagelike and axislike morphological qualities. A developmental comparison of synangium development at the ultimate tips of aerial branches and of unusually elongating and normal sized fertile‐appendages showed that the morphogenetic pattern of synangium development was similar. Anatomical and morphological evidence showed the synangium to be derived from terminal subdivisions or bifurcations of the apical meristem of each structure studied. This supports the phyletic concept that the synangium of the Psilotaceae is basically terminal to an axis or an axis homologue, and that it probably evolved from terminal bifurcative branching. Occasional multiple sporangium lobes may be formed on a P. nudum synangium which may not be represented by vascular bundles. Two hypothetical phyletic models of synangium evolution are proposed that could be used to explain this phenomenon and which should be tested by further evidence. Typical and appendageless P. nudum were compared in their morphogenetic pattern developed at the upper axis vegetative apical meristem, and a reconciliation was made between the structuring of the apparently disparate forms, which involved the presence or absence of serial ordering in apical derivatives. It is suggested that this could serve as a model for appendage evolution in the family Psilotaceae.