bluuebunny/crossref_metadata_2025 huggingface dataset:
A QUANTITATIVE STUDY OF CELLULAR EVENTS IN THE SHOOT APICAL MERISTEM OF BRASSICA CAMPESTRIS (CRUCIFERAE) DURING TRANSITION FROM VEGETATIVE TO REPRODUCTIVE CONDITION
Authors: Orr Alan R.
Published: January 2018

Vegetative plants were induced to flower by 16‐hr‐long days. Apical buds were collected at intervals during several developmental phases up to 63 hr. A stereologic analysis and mitotic index study was conducted on median longitudinal sections of shoot apical meristems. A rise in the mitotic index occurred between 12 and 24 hr within central, peripheral and pithrib meristem zones. Preceding the floral stage a second increase in the mitotic index was observed in peripheral and central zones, but not in the pith‐rib meristem zone. A significant rise in apical volume, cell number, height, and width began in the transitional stage and continued to the floral stage. Significant correlation coefficients were observed between these apical parameters. Relative volume and cell population of each zone remained constant from the vegetative to the reproductive stage. Volume fraction occupied by the nucleus and nucleolus remained constant within each zone during the same time period. In each zone the volume of the nucleus was significantly correlated to volume of the nucleolus. It appears a pre‐inflorescence apex, while larger, is structurally similar to a vegetative apex.
BIOMASS, PRODUCTION, AND LITTERFALL IN THE COASTAL SAGE SCRUB OF SOUTHERN CALIFORNIA
Authors: Gray John Timothy , Schlesinger William H.
Published: January 2018

A 22‐year‐old stand of coastal sage scrub in the coastal mountains of southern California had a peak standing aboveground biomass of 1,417 g/m2, determined by dimension analysis. Annual aboveground net primary production was 255 g/m2/yr, determined by monthly twig harvests of dominant species and the clipping production of subordinate species. The stand was codominated by two drought‐deciduous species, Salvia leucophylla and Artemisia californica, which together comprised 81% of the biomass. Annual litterfall was measured at 194 g/m2/yr. These biomass, production, and litterfall values are less than those measured in most evergreen chaparral communities in California.

Seasonally, the two dominant shrubs began aboveground production in the winter soon after the first rains and continued growth for six months until early summer. A massive leaf fall occurred in May–June as the summer drought began, but twig and inflorescence production for both species continued at a high rate into the summer months. Salvia leucophylla had two shoot types: 1) an early spring canopy shoot that elongated rapidly, produced the inflorescence, and died in mid‐summer; and 2) a short side shoot produced in late spring with small dense leaves that were retained during the summer drought and early winter. Artemisia californica produced a single cohort of twigs in the early spring, most of which carried inflorescences by late summer.
THE TAXONOMIC SIGNIFICANCE OF ANTHOCHLORS IN THE SUBTRIBE COREOPSIDINAE (COMPOSITAE, HELIANTHEAE)
Authors: Crawford Daniel J. , Stuessy Tod F.
Published: January 2018

Anthochlors (chalcones and aurones) are found in a number of plant families including the Compositae. Within this family they were once thought to occur only in the subtribe Coreopsidinae of the tribe Heliantheae. More recent studies show them to occur also in the tribes Cardueae, Eupatorieae, Helineae, Inuleae, and Lactuceae. This has suggested that anthochlors are no longer good taxonomic markers for the Coreopsidinae. A survey of 69 of approximately 210 genera of the Heliantheae shows anthochlors present only in the Coreopsidinae except for Helianthus, Simsia, Tithonia, and Viguiera, closely related genera of the subtribe Helianthinae. Of the 32 genera of the Coreopsidinae recently recognized, 30 were surveyed from available material and all contain anthochlors except Guardiola and Venegasia. The results indicate that, despite some variation, anthochlors are still good taxonomic markers for the Coreopsidinae. This represents the only case within the family in which a particular type of flavonoid is taxonomically diagnostic at the subtribal level.
ANOMALOUS SECONDARY GROWTH IN LIANAS OF THE BIGNONIACEAE IS CORRELATED WITH THE VASCULAR PATTERN
Authors: Dobbins David R.
Published: January 2018

Vascular pattern and anomalous secondary growth were studied in shoots of Clytostoma callistegoides, a liana having two types of phyllotaxy, one decussate and the other whorled. In shoots with decussate phyllotaxy, typical of bignoniaceous lianas, the vascular pattern has four major vascular strands that extend continuously from internode to internode, whereas in shoots having a whorled phyllotaxy the pattern has six major vascular strands. The first unidirectional cambium segments which result in the anomalous secondary growth were initiated precisely opposite each of the major vascular strands in both types of shoots. It is concluded that positioning of unidirectional cambium segments responsible for anomalous growth is correlated morphogenetically with the vascular pattern.
ISOETES HOWELLII: A SUBMERGED AQUATIC CAM PLANT?
Authors: Keeley Jon E.
Published: January 2018

In the leaves (but not corms) of the submerged aquatic plant Isoetes howellii, malic acid concentration fluctuates from 1–3 mg g–1 FW in the evening to 7–13 mg g–1 FW in the morning. Associated with this is a change in pH (a.m. pH 3–4 vs. p.m. pH 5–6) and titratable acidity (75–200 μ eq g–1 FW change in acidity between morning and evening) of the plant extract. 14CO2‐fixation experiments indicate that carbon is fixed in both the light and the dark, though the amount of carbon fixed in the light is more than double that fixed in the dark. Autoradiographs show 89% of dark‐fixed CO2 ends up in malic acid and the remainder in citric acid, whereas these two acids constitute less than 5% of the light‐fixation products. It is suggested that CAM metabolism in this aquatic species may be related to the lower availability of CO2 for photosynthesis during the day than during the night in its aquatic environment.
FEDEKURTZIA, A NEW CARBONIFEROUS FROND FROM GONDWANALAND AND ITS FRUCTIFICATION
Authors: Archangelsky Sergio
Published: January 2018

Fedekurtzia gen. nov. is proposed for specimens referred to Archaeopteris argentina (Kurtz, 1921) from middle Carboniferous strata of the Paganzo Basin in Argentina. Similar materials from the same area were assigned to at least six different genera by later authors. A revision of specimens from various collections shows that they all belong to a single type of polymorph frond. A progymnospermous affinity is suggested by the small fructifications resembling spikes which are attached to main rachides, as well as by the helicoidal insertion and bilateral disposition of the pinnae on the main axis. Similar fronds and fructifications have been found in Australia. These are referred in part to the new genus which seems to have had a wide distribution over Gondwanaland. Paleoclimatic and palaeogeographic evidence is considered for the Carboniferous in the Gondwana Realm. Rather poor and primitive palaeofloristic associations are usually found.
THE FLORAL ANATOMY OF KOEBERLINIA ZUCC: SYSTEMATIC IMPLICATIONS
Authors: Mehta Indira J. , Moseley Maynard F.
Published: January 2018

The in toto pattern of the floral vasculature in Koeberlinia Zucc, is distinctive. The median vascular trace to each sepal is concrescent with the antesepalous stamen trace forming a trace complex. Each petal trace is concrescent with the nearest antestaminal trace, and this common trace is in turn concrescent basally with the common basal supply to the adjacent sepal margins. The ventral carpellary bundles and the ovular traces of the two carpels are arranged for part of the ventral carpellary system into an essentially continuous hollow stele‐like cylinder and many of the ovular vascular supplies originate from this strand. All vascular concrescences are congenital. Comparisons of the morphological and floral vasculature characters of Koeberlinia with those of its various putative allies revealed that there are no substantial reasons for linking Koeberlinia with Canotia, Celastraceae, Rutaceae, Simaroubaceae, or Zygophyllaceae. The in toto floral vascular structure of Koeberlinia is closely similar to that of the Caryophyllaceae and dissimilar to that of the Capparaceae. Several qualitative characters of the secondary xylem of Koeberlinia differ from those of the Capparaceae, yet certain important ones are similar. Many of the morphological characters of Koeberlinia are similar to those of the Capparaceae as well as the Caryophyllaceae, yet certain critically important ones strongly indicate a relation of Koeberlinia to the Capparaceae: occurrence of myrosin cells, capparaceous pollen, capparaceous ovular characters. To include Koeberlinia within either of these families is unwise, but the writers are inclined to retain Koeberlinia in a monogeneric family within the larger Capparales.
A COMPARISON OF ALPHA‐AMYLASES FROM THE LATEX OF THREE SELECTED SPECIES OF EUPHORBIA (EUPHORBIACEAE)
Authors: Biesboer David D. , Mahlberg Paul G.
Published: January 2018

A technique for the partial purification of α‐amylases from latex of Euphorbia heterophylla, E. marginata, and E. tirucalli is described. The enzymes were found to be similar to other higher plant amylases using the criteria of molecular weight, pH characteristics, kinetics, number of isozymes, and blue value‐reducing value patterns. Carbohydrases other than α‐amylases were not detectable in latex. The amylases were employed to examine their capacity to digest latex starch grains which are common components of the laticiferous cell in this genus. Laticifer starch grains are not susceptible to in vitro amylolysis. Removal of the starch grain membrane with Triton X‐100, damaging the grain, or treating the grains with α‐amylases from diverse biological sources had little effect upon hydrolysis. Grains incubated with pullulanase followed by α‐amylase caused a slight but significant increase in hydrolysis of raw laticifer starch grains. These studies indicate that the nonarticulated laticifer in Euphorbia is a cul de sac for certain primary and secondary metabolic products and that the indigestible and morphologically complex starch grains in the latex have evolved to function in a secondary role within the laticifer.
THE SPORE‐GERMINATION PATTERN OF THELYPTEROID FERNS
Authors: Huckaby Clark S. , Raghavan V.
Published: January 2018

Cell division patterns in germinating spores of several Thelypteris species were studied using light microscopy of sectioned material and scanning electron microscopy. All species exhibited the same basic germination pattern, characterized by an asymmetric cell division of the spore parallel to the equatorial plane to delimit a proximal rhizoid, followed by a perpendicular division of the basal cell to form the protonemal cell. While spore‐germination patterns appear to be a potentially useful taxonomic character in some groups of ferns, the homogeneity in this character exhibited by the thelypteroid group impairs its usefulness in the taxonomy of Thelypteris.
A MORPHOMETRIC STUDY OF THE ULTRASTRUCTURE OF ECHINOCEREUS ENGELMANNII (CACTACEAE). III. SUBAPICAL AND MATURE TISSUES
Authors: Mauseth James D.
Published: January 2018

A stereological, morphometric study of the ultrastructure of subapical cells, xylem parenchyma, and cortical chlorenchyma of Echinocereus engelmannii shows that each of these cell types has a unique organellar composition. The cells of any of these tissues are unique not only in vacuolation (which is visible at the light microscope level), but also in the nucleus/cytoplasm ratio and the concentrations of mitochondria, chloroplasts, and dictyosomes. Furthermore, the differences between each of these cell types were large and statistically significant. It had previously been found that the cells of each zone of the shoot apical meristems of E. engelmannii are different from those of the other zones, but the present study suggests that, considering the large ranges of structure possible in the nonapical cells of this species, the apical meristem variation should be considered as only a minor difference and that the meristem zones are really quite similar to each other.
ACCELERATION OF PLANT GROWTH THROUGH SEED TREATMENT WITH BRASSINS
Authors: Gregory Luis E.
Published: January 2018

Treating barley seeds with brassins in methylene chloride before planting, accelerated plant growth in the greenhouse and growth chamber. A biologically active consituent of brassins is the steroid, brassinolide [2α, 3α, 22(R), 23(R)‐tetrahydroxy‐24(S)‐methyl‐β‐homo‐7‐oxa‐5α‐cholestan‐6‐one]. Plants from the treated seeds attained full leaf development sooner than did plants from untreated seeds. Both leaf and tiller growth was accelerated, provided that an adequate amount of radiant energy was maintained. Brassin treatment reduced the phenotypic variability of the seedlings.
THE VASCULAR SYSTEM OF DOLEROTHECA AND ITS PHYLOGENETIC SIGNIFICANCE
Authors: Dufek Debra , Stidd Benton M.
Published: January 2018

The course of the vascular system in the proximal end of Dolerotheca formosa is described. Vascular bundles flare outward and downward immediately upon entering from the peduncle. These bundles are located in radiating septa just beneath the cover and give off small lateral bundles pinnately. Laterals from adjacent septal bundles meet, fuse, and extend downward in the parenchyma plate separating paired sporangia. The septal bundles, therefore, alternate in position with the parenchyma plate bundles and are interpreted as remnants of an ancestral bifurcating pinna system, which bore pendent sporangia along each side of supporting rachises. This interpretation differs from both the Codonotheca aggregation and plicated Whittleseya hypotheses recently advanced to explain the evolutionary pathway by which this complex pteridosperm pollen organ evolved.
GENETIC PATTERNS ASSOCIATED WITH GROWTH VARIABILITY IN PONDEROSA PINE
Authors: Knowles P. , Grant M. C.
Published: January 2018

Variability in annual growth increment in Pinus ponderosa was measured and heterozygosity level estimated in order to examine the relationship between genetic heterozygosity and phenotypic homeostasis in natural populations of a long‐lived perennial plant. Pollen was collected from 190 ponderosa pine trees in the upper montane region of the Front Range in Colorado and four isozyme systems were resolved electrophoretically from these samples. Each tree was cored, aged, and each annual ring width measured. Statistics estimating within‐tree variation in growth increment were then related to heterozygosity levels. The results indicated a significant positive association between level of heterozygosity and growth variability. Two speculations are offered to account for this relationship.
A COMPARISON OF CHROMOSOME KNOB FREQUENCIES BETWEEN SYMPATRIC AND ALLOPATRIC POPULATIONS OF TEOSINTE AND MAIZE
Authors: Smith J. S. C. , Goodman M. M.
Published: January 2018

Unrestricted gene flow would be expected to lead to similar chromosome knob frequencies in sympatric populations of maize and teosinte. Chi‐square tests were therefore used to compare chromosome knob frequencies of 45 collections of Mexican teosinte, grouped according to six geographic regions, with sympatric and allopatric populations of maize. Comparisons of knob frequencies between sympatric and allopatric populations within each region produced an initial classification for each knob‐forming position. Further comparisons for each knob position over all regions, led to an interpretation of results for sympatric populations of maize and teosinte in terms of gene flow, selection, differentiation, ancestral similarities, and ancestral differences. Within regions, a high number of knob positions suggesting gene flow was associated with a low number of knob positions suggesting recent differentiation, and vice versa. It is suggested that the teosinte populations most likely to represent unique sources of germplasm are those most susceptible to future genetic erosion by maize. These relationships may represent a general model applicable to a number of crop plants and associated weed races.
THE INFLUENCE OF INDIVIDUAL EMBRYONIC TISSUES ON THE MORPHOLOGY AND DEVELOPMENT OF ZEA MAYS (POACEAE) GERMLINGS
Authors: Tilton Varien R.
Published: January 2018

Mature embryos of Zea mays L. (inbred A188) were used in this study, which was undertaken to investigate three questions: 1) do all embryonic tissues of Zea, viz., coleoptile, scutellum, epicotyl, mesocotyl, hypocotyl, and coleorhiza, influence germling morphology and growth; 2) if a given tissue does exert an influence, what is it, and 3) what effect does removal of one tissue have on that tissue and on the tissues remaining? Experimental results revealed growth of isolated epicotyls was greater than that of epicotyls still attached to the scutellum, but it was less than that of whole embryo controls. Isolated hypocotyls grew less than any other tissue except scutella, which seemed to have no growth response. Hypocotyls still attached to the scutellum had the greatest growth response of all tissues. Intact embryo axes had a response intermediate to whole embryo controls and isolated epicotyls. Growth of the epicotyl is influenced most strongly by the hypocotyl, and growth of the hypocotyl, by the scutellum. The mesocotyl does not appear to have a regulatory influence on other tissues. It is proposed that the scutellum synthesizes or otherwise provides a growth factor (nutrients, growth regulator, or combination thereof) which is the initial stimulus for hypocotyl and root growth during germination, and that the epicotyl has a regulating influence on this factor in germlings and young seedlings.
OBSERVATIONS ON A FIRE‐ADAPTED BAMBOO OF THE BRAZILIAN CERRADO, ACTINOCLADUM VERTICILLATUM (POACEAE: BAMBUSOIDEAE)
Authors: Soderstrom Thomas R.
Published: January 2018

Taquari is the common name of a bamboo that occurs in the cerrado biome of central Brazil where it is subjected to long dry seasons and periodic fires. The buds of the culm are covered by hard scales that protect them during the dry season. The pachymorph rhizomes with short necks form a dense underground system that also aids in carrying the plant through this hostile period. The buds of the upper nodes of the culm begin growing during the wet season and produce horizontal subequal branches that do not rebranch. Those of the lowermost nodes, which occur at ground level or just below, are apparently specialized to break into growth only after fire. Although homologous to the buds of the upper nodes, those at the base of the plant produce tall, erect branches that rebranch and take on the appearance and function of the culms that were destroyed by fire. The spikelet, type of inflorescence, and fruit (achene) indicate that taquari should not be retained in Arundinaria, where originally described, or in Rhipidocladum, where recently transferred, but deserves recognition as a distinct genus, which is here given the name, Actinocladum. Included are complete descriptions of the new genus and its sole species: A. verticillatum (Nees in Martius) McClure ex Soderstrom.
VALLITHECA VALENTIA GEN. ET SP. NOV., PERMINERALIZED SYNANGIA FROM THE MIDDLE PENNSYLVANIAN OF OKLAHOMA
Authors: Mapes Gene , Schabilion J. T.
Published: January 2018

Vallitheca valentia gen. et sp. nov. is a permineralized, synangiate fructification of probable seed fern affinities from the Wewoka Formation (Desmoinesian) near Ada, Oklahoma. Synangia are oblong to pyriform, average 1 cm long, and contain 32 to 48 tubular sporangia embedded proximally in ground tissue. The sporangia are arranged within the synangia in a unique pattern: a ring of peripheral sporangia dehisces toward the center of the synangium and a central group of sporangia dehisces outward. This unique arrangement is unlike that of any currently recognized group.
CYTOGENETICS OF AGROPYRON FERGANENSE AND ITS HYBRIDS WITH SIX SPECIES OF AGROPYRON, ELYMUS, AND SITANION
Authors: Dewey Douglas R.
Published: January 2018

Meiosis and mode of reproduction are described in Agropyron ferganense Drob., a perennial forage grass from Central Asia. This species is diploid (2n = 14); it exhibits normal meiosis and reproduces by cross‐pollination. Hybrids were produced between A. ferganense and six species with known genome formulas: 1) North American A. spicatum (Pursh) Scribn. & Smith, an SS diploid (2n = 14), 2) Middle Eastern A. libanoticum Hack., an SS diploid (2n = 14), 3) North American A. dasystachyum (Hook.) Scribn., an SSHH tetraploid (2n = 28), 4) Eurasian A. caninum (L.) Beauv., an SSHH tetraploid (2n = 28), 5) North American Sitation hystrix (Nutt.) J. G. Smith, an SSHH tetraploid (2n = 28), and 6) South American Elymus patagonicus Speg., an SSHHHH hexaploid (2n = 42). Almost complete chromosome pairing in the A. ferganense x A. spicatum and A. libanoticum hybrids demonstrated that A. fergenanse is an SS diploid, but it is genetically isolated from the other SS diploids because of high sterility in the F1 hybrids. S‐genome diploids form a network of species that extend from the Middle East through Central Asia to western North America. Frequent occurrence of seven univalents and seven bivalents at metaphase I in the triploid hybrids of A. ferganense x A. dasystachyum, A. caninum and S. hystrix was consistent with the proposed genome formulas of SS for A. ferganense, SSHH for the three tetraploid species, and SSH for the hybrids. Chromosome pairing was highly variable in the A. ferganense x E. patagonicus hybrids; however, some cells had almost complete bivalent pairing, an expected observation in an SSHH hybrid from a cross between an SS diploid (A. ferganense) and an SSHHHH hexaploid (E. patagonicus). Various options were considered concerning the appropriate generic classification of the S‐genome diploids, which are now commonly placed in Agropyron. The inclusion of these species in the genus Eiytrigia, as advocated by some Soviet taxonomists, appears to be a reasonable decision.
FLOWER COLOR POLYMORPHISM AND POLLINATION BIOLOGY OF PLATYSTEMON CALIFORNICUS BENTH. (PAPAVERACEAE)
Authors: Hannan Gary L.
Published: January 2018

Five genetically controlled flower color morphs in Platystemon californicus tend to occur in distinct geographic regions, suggesting regional selection of morphs. I examined the reproductive biology of P. californicus to determine whether color morphs are subject to selection due to differences in pollinator attractiveness. Plants of P. californicus have a high pollen: ovule ratio and are highly self‐incompatible. Solitary bees (Andrenidae and Halictidae) are the most effective pollen vectors, but show inconsistent discrimination among color morphs. Platystemon californicus is unusual among annual self‐incompatible plants in that wind is an important pollen vector. As a result of wind pollination, most polymorphic populations show no intermorph seed‐set differences. Therefore, the geographic distribution of flower color morphs cannot be explained by differential attractiveness of color morphs to pollinators in different regions. Any selective value of color morphs must be due to linkage of flower color with as yet undetected morphologically or physiologically adaptive characters.
MITOSIS AND CYTOKINESIS IN THE PRASINOPHYCEAE. I. MANTONIELLA SQUAMATA (MANTON AND PARKE) DESIKACHARY
Authors: Barlow Steven B. , Cattolico Rose Ann
Published: January 2018

Mitosis in Mantoniella squamata (Manton and Parke) Desikachary, a small scale‐covered green monad, is presented. Organelle replication precedes nuclear division and begins with the replication of the chloroplast. As the chloroplasts separate, the Golgi and flagellar apparatuses divide. The discoid microbody enlarges and becomes ‘V'‐shaped, with the arms extending toward depressions in the pyrenoid stalks of the chloroplasts. At prophase, microtubules produced by an amorphous microtubule organizing center enter the nucleus via polar fenestre. The nuclear membrane remains intact. As the chloroplasts migrate further apart, the spindle pole‐to‐pole distance increases. By metaphase, daughter‐cell lobes are discernible as a cleavage furrow, which appears as early as prophase, and begins to incise the cell. A single Golgi apparatus is situated near the spindle pole; the flagellar apparatus lies adjacent to the pole. The cleavage furrow continues to constrict the cell, resulting in a narrowing isthmus containing the elongate microbody, nucleus and a rootlet system connecting the basal bodies of the daughter flagella. At telophase, no extra‐nuclear microtubular systems other than the previously observed rootlet are present and the nuclei remain separated from each other. In cells undergoing multiple divisions to produce more than two daughter cells, the orientation of organelles changes somewhat, with the basal bodies and the Golgi apparatus separating daughter nuclei prior to the onset of cytokinesis. The mechanics of mitosis in Mantoniella are compared with other green monads and the evolutionary implications discussed.
EFFECT OF ETHYLENE ON AERENCHYMA DEVELOPMENT
Authors: Kawase Makoto
Published: January 2018

When applied to a part of stem or basal part of stem and root system, 1 ppm ethylene induced lysigenous aerenchyma development in the stem cortex of Helianthus annuus, Lycopersicon esculentum, and Phaseolus vulgaris. Local application of ethylene to a part of stem significantly increased the activity of cellulase in that part of stem in the above three species. Pretreatment of a part of stem with 100 ppm AgNO3 counteracted the effects of ethylene which was subsequently applied to the part of stem, completely suppressing aerenchyma development and highly significantly reducing cellulase activity in Helianthus annuus. These results support the earlier proposal that the deficiency of oxygen in waterlogged plants triggers the anaerobic stimulation of ethylene production, which in turn increases the cellulase activity leading to aerenchyma development.
PETIOLE DEVELOPMENT AND XYLEM DIFFERENTIATION IN XANTHIUM REPRESENTED BY THE PLASTOCHRON INDEX
Authors: Maksymowych Roman , Maksymowych Andrew B.
Published: January 2018

Petiole development and formation of xylem vessels have been investigated in Xanthium leaves from early ontogeny to maturity. Kinetics of growth was presented in terms of absolute and relative elemental rates of elongation. The process of vascularization was assessed by the number of differentiated xylem vessels. The leaf plastochron index (LPI) developed by Erickson and Michelini (1957) was used for designating the various stages of development. An exponential increase in petiole length was observed between the LPIs –3 and +4 indicating a constant relative rate of 0.20 or 20% increase per day. After cessation of lamina elongation at LPI 8, petiole elongation continued for an additional 5 day period, to LPI 9.5. Relative elemental rate analysis revealed that the basipetal pattern of elongation was maintained throughout the leaf development. At a specific plastochron age, the only growth was due to the petiole elongation. Leaves which ceased elongating had not completed their internal development, since the process of xylem formation continued for several plastochrons, or about 8 days. The highest rate of xylem formation was ten vessels per day at LPI 5. On the average, about five xylem vessels differentiated per day in the middle portion of a Xanthium petiole. Mature petioles contained an average of 218 xylem vessels. About 12 canals of schizogenous origin preceeded the development of the vascular tissue.
HISTOLOGICAL EFFECTS OF AQUEOUS ACIDS AND GASEOUS HYDROGEN CHLORIDE ON BEAN LEAVES
Authors: Swiecki Tedmund J. , Endress Anton G. , Taylor O. Clifton
Published: January 2018

Primary leaves of Phaseolus vulgaris L. (pinto bean), 9 or 12 days from sowing, were exposed to aqueous acids, chloride salts, or hydrogen chloride gas. Leaves were examined for the presence and severity of resultant visible injury and sampled for light and scanning electron microscopy. Exposure to 0.06 n HCl, HNO3, H2SO4 or 14.5–19.0 mg m‐3 gaseous HCl for 20 min evoked similar foliar injury including glazing and necrosis of the laminas. This injury appeared to result initially from plasmolysis and collapse of the epidermis and subsequently of the underlying mesophyll. Cellular injury was accompanied by various cytoplasmic alterations. Microscopic symptoms observed in leaves exposed to gaseous HCl or aqueous acids included vesicles and particulates within the larger vacuoles. Similar symptoms were present in leaves exposed to polyethylene glycol 6000. Differential effects included formation of necrotic “pits” and preferential injury to paravascular tissues in leaves treated with aqueous acids and crystalline chloroplast inclusions in gaseous HCl‐treated and water‐stressed leaves. The visible and microscopic appearances of leaves exposed to aqueous acids or gaseous HCl were compared and related to injury stemming from acid precipitation and a possible mechanism of action for gaseous HCl phytotoxicity.
COLONIZATION AND COMMUNITY STRUCTURE OF TWO PERIPHYTON ASSEMBLAGES, WITH EMPHASIS ON THE DIATOMS (BACILLARIOPHYCEAE)
Authors: Hoagland Kyle D. , Roemer Stephen C. , Rosowski James R.
Published: January 2018

Examination of the three‐dimensional structure of periphyton communities through time indicated that their microsuccession is analogous to higher plant succession. The development of attached diatom communities in two reservoirs was studied using artificial substrates, and the morphology of dominant organisms, patterns of spatial heterogeneity, and community interactions were documented with scanning electron microscopy. Of 93 taxa found,Gomphonema parvulum, G. olivaceum, Navicula graciloides, Nitzschia palea, andN. dissipatawere dominant, depending upon season and reservoir. Comparisons of community diversity (SIMI) between reservoirs within seasons ranged from 0.023–0.843 (median = 0.254), indicating that the reservoirs were quite different with respect to diatoms present and their apportionments. Colonization was slow the first 2 wk in spring and fall, and throughout winter, but rapid during summer. Shifts in numerical dominance between certain species occurred in fall, spring, and summer. These inverse correlations of abundances and the functional dominance of overgrowth suggested competition for substrate surface area in the periphyton. The colonization sequence was often predictable—a presumably organic coating and a variety of bacteria, followed by low profile diatoms, and finally an upperstory of long‐stalked and large‐rosette diatoms and filamentous green algae. Periphyton microsuccession is similar to higher plant succession in the consistent change in vertical community structure from low to high physical stature, in the association of numerical dominance with large stature (via cell size or long mucilaginous stalks), and in the progressive slow‐down in the rate of succession. Diatom mucilage also contributed to community structure by binding particulates and entrapping other algae and serving as the mechanism for substrate attachment.
EUPHORBIOID INFLORESCENCES FROM THE MIDDLE EOCENE CLAIBORNE FORMATION
Authors: Crepet William L. , Daghlian Charles P.
Published: January 2018

Inflorescences from the Claiborne Formation of western Tennessee are remarkably similar to those of the tribe Hippomaneae, subfamily Euphorbioideae, of the Euphorbiaceae. The fossil inflorescences are spikes of bract‐subtended cymules of at least three florets each. Florets are composed of at least three stamens. Palynological features of the fossils are also shared by the Hippomaneae. Fossil pollen is tricolporate, prolate (26.9 × 20.6 μm; P/E = 1.3), with lalongate pores. Exine structure is tectate columellate with a perforate tectum. The exine is reticulate and the muri are conspicuously striate. These specimens represent the first fossil floral evidence of the Euphorbiaceae. It is surprising that inflorescences of the Hippomaneae so modern in aspect existed in the Middle Eocene, since the tribe is universally considered to be one of the most advanced in the family.
POST‐POLLINATION PHENOMENA IN ORCHID FLOWERS. XI. AUTOGAMY IN PHAJUS TANKERVILLIAE (AITON) BL, ORCHIDACEAE
Authors: Gandawidjaja Djunaidi , Arditti Joseph
Published: January 2018

In autogamous blossoms ofPhajus tankervilliae, which do not open fully, the pollen drops into the stigma while flowers are still in the bud stage or as the perianth segments separate lightly. Post‐pollination phenomena exhibited by autogamous flowers do not differ from those of allogamous ones. The naturalization ofP. tankervilliaein areas to which it was brought as a horticultural plant may be due to the introduction of autogamous forms.
HORMONES AND EARLY IN VITRO DEVELOPMENT OF EPIPHYLLOUS PROPAGULES ON BRYOPHYLLUM CALYCINUM
Authors: Karpoff Arnold J.
Published: January 2018

Uniform leaf discs of Bryophyllum calycinum, each containing a single marginal notch, were explanted onto sterile media. These media contained the minerals and vitamins of Murashige and Skoog, 2% sucrose, and 1% agar. Hormones used included indoleacetic acid (IAA), gibberellic acid (GA), 2,4‐dichlorophenoxyacetic acid (2,4‐D), and benzylaminopurine (BAP). Explants were grown for 1 wk at which time the length of the longest leaf was measured. These observations represent the most rapid in vitro development of these isolated structures yet reported in the literature. The number of roots was also recorded and the average length of the two longest roots was calculated. BAP at concentrations of 10‐6 to 10‐8 m provided the only growth stimulation of the propagules observed, while 10‐4 m completely inhibits roots and reduces leaf development by 60% and 10‐5 m significantly decreases number and length of roots. Except at 10‐3 m, which was inhibitory, IAA had no effect on propagule leaf development. Concentrations of 10‐3 m 2,4‐D induced callus and no roots, 10‐4 m induced both callus, leaves, and roots, and multiple root primordia at the notch in explants grown for 2 wk at 10‐4 m. When callus formed it never arose at a cut surface, but broke through the epidermis only at the notch of the leaf. Gibberellic acid and 2,4‐D were generally inhibitory to leaf development but 10‐5 m GA significantly enhanced root length. With the exception of 10‐5 m GA, both 2,4‐D and GA generally inhibit both average length of longest two roots and average number of roots. Concentrations of BAP of 10‐7 m and 10‐8 m stimulated root production as did 10‐7 m IAA and 10‐7 m 2,4‐D while other concentrations of hormones used were either without effect or were inhibitory.

Gibberellic acid at 10‐4 m produced leaves without any of the notches typical of this species. As the concentration of the hormone was reduced to 10‐5 m notches began to be formed and by 10‐6 and 10‐7 m normal notching was restored.
QUANTITATIVE STUDIES OF THE ROOT APICAL MERISTEM OF EQUISETUM SCIRPOIDES
Authors: Gifford Ernest M. , Kurth Eva
Published: January 2018

An investigation was made of the meristematic activity of the apical cell, its immediate derivatives (merophytes), and of other selected cell populations of the root of Equisetum scirpoides Michx. The plane of the first division of a derivative of the apical cell is radiallongitudinal, which provides evidence that merophytes immediately adjacent to the apical cell cannot be the ultimate root initials. The apical cell is as active mitotically in roots 20–40 mm long as it is in roots that are 0.25–1 mm in length. The mitotic activity of the apical cell and of other cell populations was determined from the mitotic index, and from determination of the durations of the cell cycle and of mitosis of the apical cell by using the colchicine method of metaphase accumulation. Microspectrophotometric measurements of DNA content indicated that there was no consistent increase in DNA (endopolyploidy) in the apical cell or in the other meristematic cells as roots increased in length. Conclusion: there is no evidence that the apical cell becomes quiescent or undergoes endopolyploidy as a root increases in length.
SPECIAL PAPER: A REVIEW OF RECENT RESEARCH ON THE CATHAYSIA FLORA IN ASIA
Authors: Xingxue Li , Zhaoqi Yao
Published: January 2018

This paper attempts to give a brief review of research on the Cathaysia flora during the last 20 years in China and other countries. The paper also briefly discusses the origin, development, migration and extinction of this flora from the Late Carboniferous to the close of the Permian.
CYTOGENETIC ANALYSES OF AUTOPOLYPLOIDS: MODELS AND METHODS FOR TRIPLOIDS TO OCTOPLOIDS
Authors: Jackson R. C. , Casey Jane
Published: January 2018

Methods are presented for determining the frequencies and numbers of various meiotic configurations expected in autopolyploids. This allows one to test polyploids of unknown origin for agreement with expected meiotic configurations. Rejection of the autoploid hypothesis may indicate the presence of Ph‐like genes or some type of alloploid. The models consider mean chiasma frequencies of 2, 3, and 4 per bivalent for triploids and tetraploids and 2 per bivalent for pentaploids, hexaploids, heptaploids, and octoploids. Literature data for a known autotriploid, autotetraploids, allotetraploids, and allopentaploids were tested against expectations of the models. There was generally good agreement between number of observed autoploid meiotic configuration and those expected in the models.
THE INTERFACE BETWEEN COTTON TISSUE AND A PENETRATING NOBLE METAL PROBE
Authors: Goldstein A. H.
Published: January 2018

A passive system that may be useful for measuring changes of the redox potential of in vivo, extracellular plant tissue has been developed within the past few years. The technique involves the placement of a small (250 μm diam) noble metal probe into the anatomical region of interest and subsequent monitoring of the time variation in the measured electrode potential of this probe. The result of this measuring technique has been termed an electrophytogram. The observed voltage fluctuations may be empirically correlated with several observable plant growth phenomena. However, elucidation of the physiological basis for electrophytograms must involve the proper anatomical interpretation of the position of the probe relative to the plant tissue. This paper reports the results of freeze‐fracture electron microscopic examination of the probe/tissue interface after wound healing has occurred. Electron micrographs clearly show cell wall material, appressed directly against the probe. These results indicate that the electrophytogram system provides a method for monitoring the electrochemical status of the cell wall space. Insertion of the probe into mature, fully elongated tissue appears to cause little physical damage to non‐xylem tissue organization beyond the adjacent cell layers and virtually no damage to the xylem region.
ROOTS OF SOBRALIA MACRANTHA (ORCHIDACEAE): STRUCTURE AND FUNCTION OF THE VELAMEN‐EXODERMIS COMPLEX
Authors: Benzing D. H. , Ott D. W. , Friedman W. E.
Published: January 2018

Roots of Sobralia macrantha, a largely terrestrial orchid, bear a typical multilayered velamen underlaid by a cortical exodermis. The latter consists of densely cytoplasmic passage cells regularly interspersed among much larger, elongate, vacuolate cells. A structure which may be peculiar to Sobralia, or at least unusually well developed there—the fibrous body—consists of numerous intermeshed and divided wall outgrowths arising from two or three velamen cells positioned directly over the passage cell. This body is well designed to retard root transpiration. Should the fibrillar components be appropriately hygroscopic, it may act as a valve, promoting movements of water into the cortex while the velamen is engorged. The general mode of moisture and mineral procurement proposed for the Sobralia macrantha root probably applies to many other soil‐ and canopy‐dwelling orchids with a velamen‐exodermis complex.
EVIDENCE FOR GENETIC HETEROZYGOSITY IN A HOMOSPOROUS FERN
Authors: Gastony Gerald J. , Gottlieb Leslie D.
Published: January 2018

Homosporous fern sporophytes from natural populations exhibited heterozygous electrophoretic patterns for several enzyme systems. Genetic tests utilizing individual gametophytes demonstrate that the observed heterozygosity is coded by alleles at single loci. This simple procedure makes it possible to distinguish segregating from fixed or phenotypic heterozygosity, previously a problem in homosporous vascular plants.
UNILATERAL HYBRIDIZATION IN AUREOLARIA RAF. (SCROPHULARIACEAE)
Authors: Bell C. Ritchie , Musselman Lytton J.
Published: January 2018

A review of the slowly accumulating data on artificial hybridization in the genus Aureolaria shows a pattern of unilateral hybridization (or unilateral incompatibility) indicative of a type of homomorphic gametophytic self‐incompatibility system, involving multiple S alleles at a single locus, which has been found and genetically analyzed in plants of a few genera of both the Solanaceae and Scrophulariaceae. In such systems, if well developed, the pollen of the self‐compatible (SC) plants (in this case the annual A. pedicularia) will not grow on the stigma of the self‐incompatible (SI) plants (here the three perennial species of Aureolaria) but the reciprocal cross would be effective and the hybridization would thus be unilateral. The fact that some SI stigma x SC pollen crosses were successful indicates a relatively recent evolutionary age for the less strongly developed (Sc) system in A. pedicularia.
STRESS MODIFICATION OF ALLELOPATHY OF HELIANTHUS ANNUUS L. DEBRIS ON SEED GERMINATION
Authors: Hall Anthony B. , Blum Udo , Fites Roger C.
Published: January 2018

Helianthus annuus L. variety “Russian Mammoth” was grown in pots, in both the greenhouse and the field, under density treatments of 1, 3, 6 or 12 plants per pot and nutrient treatments of full‐strength, ½, ¼, ⅛ or 1/16 strength Hoagland's solution. The plants responded in typical fashion to both nutrient and density stress. Within each nutrient treatment, as the density of planting increased, biomass per pot first increased and then leveled off while biomass per plant decreased. Within each density treatment, as the nutrient level decreased, biomass per pot and per plant decreased. Therefore, both nutrient and density treatments imposed a stress (measured as a reduction in biomass) on individual H. annuus plants.

Total phenolic compounds from the Helianthus annuus tissue, expressed as chlorogenic acid equivalents and determined by the PVP method, increased with increasing nutrient stress (i.e., lower nutrient availability); however, increasing density stress failed to significantly modify total phenolic compounds. The maximum total phenolic level determined for field‐grown plants (69.70 mg g‐1 tissue) was approximately 58% greater than that found for greenhouse‐grown plants (44.16 mg g‐1 tissue).

When coarsely ground H. annuus plant material from the stress studies was added to soil, there was a significant depressive effect on germination of Amaranthus retroflexus seeds. In these germination was more closely correlated with total phenolic compounds (chlorogenic acid equivalents) added to the soil by the debris than with any other variable measured. Correlations were best for phenolic values of 200 μg g‐1 soil or greater.

Chlorogenic acid (an abundant phenolic acid present in H. annuus) did not inhibit A. retroflexus seed germination when added to soil in pure form.

The addition of a nutrient solution to soil containing H. annuus debris reduced subsequent inhibition of A. retroflexus seed germination.
COMPARATIVE REPRODUCTIVE BIOLOGY OF HERMAPHRODITIC AND MALE‐STERILE IRIS DOUGLASIANA HERB. (IRIDACEAE)
Authors: Uno Gordon E.
Published: January 2018

A comparative study of the reproductive biology of male‐sterile and hermaphroditic plants in a gynodioecious population of Iris douglasiana Herb. (Iridaceae) was conducted at the University of California's Marine Laboratory at Bodega Bay, California, between 1976–1979. Each year of the study, there were 11.1% male‐sterile plants in the population, some of which began blooming at the same time as the earliest blooming hermaphrodites. Male‐sterile flowers made up between 7–21% of the flowers produced during the male‐sterile flowering period.

Male‐sterile flowers had smaller sepals and petals than hermaphrodites, there were fewer of them per square meter, and they had fewer pollinated stigmas than did hermaphroditic flowers. In a test to determine pollinator preference, intact hermaphroditic flowers tended to have more pollinated stigmas than did hermaphrodites with their stamens removed or those flowers with shortened sepals made to resemble the smaller male‐sterile flowers. Floral phenology and nectar‐flow patterns were similar in both types of flowers as were the kinds of amino acids and sugar rewards in the nectar. Male‐sterile flowers, however, produced much less nectar per flower. There were no significant differences in the number of ovules per flower or the number of seeds produced per capsule between the two flower types, but the loss of seeds through larval predation was much greater in capsules from hermaphroditic flowers. Early flowering and setting of seed by plants with male‐sterile flowers could give them a reproductive advantage over plants with hermaphroditic flowers which experience higher levels of larval predation later in the growing season.
CUTICLE THICKNESS IN PHLOX AND RESISTANCE TO POWDERY MILDEW: AN UNRELIABLE LINE OF DEFENSE
Authors: Jarosz Andrew M. , Sheets Michael , Levy Morris
Published: January 2018

The relationship between leaf cuticle thickness and resistance to the powdery mildew Erysiphe cichoracearum was investigated for nine feral Phlox taxa. Cuticle thickness, the first potential host resistance feature, is variable within plants, although not correlated with leaf age, and both within and among taxa. There is also considerable variation within and among taxa in resistance response to artificial inoculations with a broadly compatible E. cichoracearum strain. However, no significant correlations between cuticle thickness and resistance were observed. The implications of these results for anti‐mildew defenses in both feral and cultivated hosts are discussed.
FLORAL DEVELOPMENT OF A FLOWER‐STRUCTURE MUTANT IN SOYBEANS, GLYCINE MAX (L.) MERR. (LEGUMINOSAE)
Authors: Johns Carol Winger , Palmer Reid G.
Published: January 2018

A flower‐structure mutant with cleistogamous flowers (but often with an exposed style and stigma) and very low seed set was found in soybeans (Glycine max (L.) Merr.). The mutant, assigned Genetic Type Collection Number T269, is controlled genetically by duplicate recessive genes, fs1 and fs2. A study of flower development in T269 plants was undertaken to determine the cause of the low seed set. Both normal and mutant flower buds were observed with a light microscope by using paraffin serial sections and with a scanning electron microscope. Measurements of various floral structures were taken to verify differences observed between mutant and normal flowers. Young mutant flower buds had longer carpels and larger receptacles than did normal flower buds. These two factors caused the sepals to be positioned abnormally, which, in turn, prevented normal development of the petals. The abnormal petal development prevented staminal tube elongation, and a spatial separation between the anthers and stigma existed at anthesis, preventing self‐pollination. Observations of the gynoecium of mutant flowers revealed that megasporogenesis and megagametogenesis were normal but that other features of ovule ontogeny were abnormal. In all ovules examined, the outer integuments failed to form micropyles. In addition, many ovules were positioned abnormally. The degree of aberration varied even within a carpel, but we estimated that at least 75% of the ovules were too aberrant to be functional. Therefore, the low seed set on T269 plants was due both to a lack of self‐pollination and to partial female sterility. It is the only naturally occurring structural sterile reported in soybeans to date.