bluuebunny/crossref_metadata_2025 huggingface dataset:
Taxonomy of the tribe Triticeae (Poaceae) using various numerical techniques. II. Classification
Authors: Baum Bernard R.
Published: May 2008

The paper reports on a study that consists of various numerical taxonomic analyses of genera of Triticeae aimed at finding intergeneric relationships based on maximum information and proposing a classificatory scheme. The data consist of morphological features, genetic relationships expressed in terms of successful crosses, and relationships assessed from the occurrence of intergeneric hybrid 'genera.' The morphological data were analysed separately in order to find out if they reflect by themselves the relationships between the genera before the data were combined with the information on crosses and on parentages of intergeneric hybrid 'genera.' The morphologic data consist of a set of 35 characters and one of 45 characters, both with equidistant states, and a set of 35 characters with weighted states. The combinations of data (morphology, crosses, and parentages) were effected through the merging of dissimilarity matrices using a few approaches such as squaring of elements of the matrices, adding the squares and taking their averages, and then taking the square roots of these averages. The relationships between the various matrices (original and combined) were assessed with Gower's technique of comparison of multivariate analyses. To find classifications, the various matrices were processed through cluster analyses. Admissible phenograms and admissible classifications were selected on the basis of a set of criteria. Subsequently, the admissible classifications were assessed using Estabrook's information theory model; a best classification was chosen. A new system of Triticeae is presented even though the data indicate clinal relationships among its members.
The status of Hordeum brachyantherum in eastern Canada, with related discussions
Authors: Baum Bernard R.
Published: May 2008

Hordeum brachyantherum Nevski (H. boreale Scrib. et Sm.) was thought, hitherto, to be disjunct with its main area in Alaska, the Rockies, and adjacent parts, and of relict nature in Newfoundland and Labrador. This study, using micromorphological characters from the lodicules and epiblasts has revealed that the eastern relict population belongs to a different species, namely H. secalinum Schreb. Since H. brachyantherum is one of the species used as bases for Fernald's "nunatak" hypothesis, the relevance of the findings of this study are discussed with reference to the hypothesis. It is suggested that H. secalinum arrived in Newfoundland and Labrador from its native western Europe by anthropochoric means.
Influence de la température sur la floraison du Lis blanc
Authors: Rivierè Simonne
Published: May 2008

The influence of thermoperiodic variations on the flowering of Lilium candidum is discussed here for the first time. Our experimentation was guided by our prior knowledge of the state of the apical meristem during the biological cycle. We concluded that forcing, to be effective, must occur on growing bulbs when the meristem of the lily is in the intermediate phase.We analyzed whether a cold period was necessary. When lily plants were cultivated for 8 days at 2 °C, the meristem reached the prefloral state at the beginning of the warm period (15 °C) which followed. The inflorescence is then in full bloom during the hot period (22 °C). Flowering occurs at the end of February.However, if the cold period is eliminated (with no change in the other periods), the terminal meristem loses its activity and differentiates. It is replaced by a small cluster of meristematic cells. A bulb develops at the top of the stem replacing the inflorescence. In this case, meristematic activity now begins at the axil of the leaves and the aerial stem. The axillary buds thus produced are a result of the combined actions of suppression of apical dominance after the loss of terminal meristem activity and the application of hot temperatures (22 °C).
Growth and sporulation of Cercospora cruenta and Cercospora canescens in culture
Authors: Ekpo E. J. A. , Esuruoso O. F.
Published: May 2008

Ten culture media were tested for their effect on growth and sporulation of Cercospora cruenta and C. canescens isolated from field-infected cowpea (Vigna unguiculata). There was very little mycelial growth and little or no conidia production on most media. Oxoid agar supplemented with V-8juice supported best growth and conidial production. Flooding V-8 juice agar with a conidial suspension resulted in multiplicity of tiny colonies with resultant increased sporulation. Conidia produced in culture were slightly longer than those produced in lesions on field-infected leaves and the degree of septation varied with the type of culture media. The width of conidia showed no apparent variation regardless of the culture media. More active mycelial growth but less conidial production was observed at agar concentration of 3% than at lower concentrations. Optimum temperature for mycelial growth and conidial production was 24–25 °C. Growth and conidial production were inhibited in complete darkness but stimulated by light.
Additional bryophytes from Nahanni National Park and vicinity, Northwest Territories, Canada
Authors: Steere William C. , Scotter George W.
Published: May 2008

Additional fieldwork in Nahanni National Park and vicinity has added 91 species of bryophytes to the flora of that region. Twenty of these are new to the District of Mackenzie, and 37 are new to the Northwest Territories of Canada. Three species, Barbula coreensis (Card.) Saito, B. maxima Syed & Crundw., and B. perobtusa (Broth.) Chen are new to North America.
A numerical taxonomic analysis of the Daucus carota complex
Authors: Small Ernest
Published: May 2008

A variety of numerical taxonomic procedures was employed to assess variation of 437 diverse populations of Daucus carota sensu lato, grown under controlled conditions, and of 100 herbarium sheets. The domesticated plants proved to be sharply discontinuous from the wild plants. In contrast with wild plants, domesticated plants possess relatively brittle, palatable, pigmented, larger, unbranched storage organs, fewer but larger relatively erect leaves, strict biennialness, larger fruits, comparatively rapid growth, relatively foliose involucral bracts, fewer central purple flowers in the umbels, smaller petals, fewer fruit spines, brittle mericarp spine hooks, and basally branched primary mericarp bristles. The first 11 differences are interpreted as the direct or indirect results of directional selection by man. The last six differences are hypothesized to be changes resulting from lack of stabilizing selection for characters of value in the wild. Domesticated carrots range from primitive Asian ('eastern') variants with yellow and purple storage organs and poorly dissected gray–green pubescent foliage to the familiar advanced type of ('western') cultivar with orange roots and highly dissected, relatively unpubescent yellow–green foliage. Numerical analysis indicated that an uninterrupted spectrum of variants connect these two kinds, and whereas two comprehensive groups of cultigens are distinguishable, any line of demarcation is arbitrary. The two kinds of cultigens are recognized as D. carota subsp. sativus var. sativus ('western carrot') and D. carota subsp. sativus var. atrorubens ('eastern carrot'). Wild carrots proved to be separable into two overlapping comprehensive groups, which were informally labelled subspecies aggregate gingidium and subspecies aggregate carota (the latter assemblage also encompassing the cultigens). Subsp. agg. carota primarily includes cosmopolitan weedy variants, some of which may have contributed germplasm to the cultivars. More importantly, this group contains an inconspicuously differentiated Asian subgroup which was found likely to represent the primary ancestor of the domesticated carrot, as evidenced by similarity with the primitive cultigens studied.
Developmental anatomy of a dimitic basidiomycete, Pterula sp.
Authors: McLaughlin Esther G. , McLaughlin David J. , Adson David E.
Published: May 2008

Developmental anatomy of fruitbodies and mycelium in a clavarioid fungus, Pterula sp. (Aphyllophorales), was studied in the light microscope using plastic-embedded material and in the scanning electron microscope. Differentiation of skeletal and generative hyphae and of the hymenium and sclerotioid patches were similar in the fruitbody and mycelium. Experimental results indicated that the hymenium is ageotropic and that fertile fruitbodies form in both upright and inverted cultures. The nature of the skeletal hyphae, and generic delimitations in the Pterulaceae are discussed.
Effect of sodium selenate, selenomethylselenocysteine, and methylcysteine on organogenesis in detached leaves of Echeveria elegans
Authors: Stewart J. M. , Nigam S. N. , Raju M. V. S. , McConnell W. B.
Published: May 2008

Detached leaves of Echeveria elegans were cultured aseptically on White's nutrient medium containing Na2SeO4 or Se-methylselenocysteine or S-methylcysteine. Both organic and inorganic selenium compounds had a greater inhibitory effect on leaf regeneration than the organic sulfur compound. While the callus formation appeared to be normal, the selenium compounds had considerable inhibitory effect on organogenesis. The sulfur compound was observed to be inhibitory at higher concentrations. Present results suggest that Se-methylselenocysteine inhibits organogenesis in E. elegans, a nonaccumulator.
Changes in the shoot apex of Streptocarpus nobilis under conditions of photoperiodic induction
Authors: Handro Walter , Monteiro-Scanavacca Walkyria R.
Published: May 2008

The structural changes in the shoot apex of plants of Streptocarpus nobilis under photoperiodic induction were studied. During flower initiation, changes in the buds occurred in a well defined sequence producing a series of characteristic stages. Some photoperiodic conditions were able to promote only the transition of vegetative to floral meristems, the floral buds remaining abortive.
Irregular flowering bud conformation in a hybrid poplar
Authors: Ronald W. G.
Published: May 2008

An unusual flowering condition in which vegetative and flowering buds occurred together at single nodes was found in a complex female poplar hybrid. The most frequent combinations consisted of vegetative buds with either one or two flowering buds. Catkins which developed from these flowering buds appeared normal; crosses to normal compatible poplars resulted in seedlings which are now being grown to flowering maturity.
Paecilomyces farinosus, the conidial state of Cordyceps memorabilis
Authors: Pacioni Giovanni , Frizzi Giuliano
Published: May 2008

Pure cultures of the very rare entomogenous ascomycete Cordyceps memorabilis Cesati, derived from both endosclerotia and ascospores, have shown that the conidial state of this fungus is Paecilomyces farinosus (Holm ex S. F. Gray) Brown & Smith. Coremia of P. farinosus were produced in culture, but the perithecia of the sexual state have not yet been obtained under artificial conditions.
Ultrastructure of spermatium ontogeny in Puccinia coronata avenae
Authors: Harder D. E. , Chong J.
Published: May 2008

Spermatium formation in Puccinia coronata avenae was concluded to be annellidic but with some phialidic analogies. The spermatiophore wall consisted of a prominent outer layer and a very thin inner layer. During formation of the first spermatium initial, the apical end of the spermatiophore became somewhat swollen and a septum was then formed centripetally at the base of the swelling to delimit the primary spermatium. The wall layers of the first spermatium were derived from the wall layers of the spermatiophore. The mature septum consisted of two bilayered walls separated by a clear septal lamella. The upper septal wall formed the basal wall portion of the preceding spermatium and the lower septal wall became the distal wall portion of the succeeding spermatium. The layers of each septal wall were confluent with the inner and outer periclinal wall layers of the developing spermatia. After spermatium secession, the broken outer wall layer left remnants as a basal frill on the spermatium and an annular scar on the spermatiophore. Each succeeding spermatium formed at a near-fixed locus on the spermatiophore. Although the formation of succeeding spermatia appeared superficially to be phialidic, examination of wall relationships indicated that the formation of each successive spermatium recapitulated the holoblastic first spermatium.As the spermatia matured, the outer wall layer, including the basal frill, gradually dissipated. The thickness of the spermatium wall was maintained by expansion of the inner layer. In mature spermatia, the inner layer comprised the bulk of the wall, and the outer layer was left as a thin tenuous band surrounding the spermatium.
Ionic dependence of deplasmolysis in the euryhaline diatom Cyclotella cryptica
Authors: Brown Lewis M. , Hellebust Johan A.
Published: May 2008

Cells of C. cryptica become plasmolyzed when subjected to a sudden increase in extracellular osmotic pressure (0.3 to 1.01 osmol/kg). Protoplasts regain their original volume if certain ionic species are present in the plasmolyzing solution. KCl is most important since it is the only electrolyte which allows deplasmolysis when supplied alone, and cells do not deplasmolyze if KCl is omitted. Ca2+, Mg2+, and Na+ are also necessary for high rates of deplasmolysis. Neither light nor ouabain have any effect on deplasmolysis rate in contrast with 2,4-dinitrophenol, which acts as a reversible inhibitor. The characteristics of deplasmolysis are consistent with a mechanism based on energy-dependent uptake of KCl, which is also affected by Na+ and divalent cations.Earlier workers in the field of permeability studies added sucrose to diatom suspensions in ion-containing media and observed plasmolysis followed by rapid deplasmolysis. This was interpreted as evidence for unusually high permeability to sucrose. The present work indicates that diatoms are impermeable to sucrose and that deplasmolysis observed by earlier workers was due to active uptake of ions rather than high permeability to sucrose. It is demonstrated that this technique can also be used for comparative studies of osmoregulation.
The Golgi cisternae of Cunninghamella echinulata
Authors: Khan S. R.
Published: May 2008

Electron microscopic investigations show that the hyphae and germinating spores of Cunninghamella echinulata (Thaxt.) Thaxt, usually contain Golgi apparatus consisting of single cisternae that are similar in structure to those of other fungi. Sometimes these cisternae show a tendency towards stacking. The Golgi cisternae exhibit a close relationship with endoplasmic reticulum and are involved in the synthesis and transport of polysaccharides. They appear to be the site of endomembrane differentiation.
Conelet abortion and ATP levels in longleaf pine
Authors: White Timothy L. , Knopp James A.
Published: May 2008

During the past 5 years, an average of 87% of the 1st year strobili in a longleaf pine seed orchard in the Sand hills region of North Carolina have aborted development. Fresh weight, dry weight, ATP, and morphological characteristics were measured periodically after anthesis to determine some of the physiological changes associated with conelet abortion. In the early stages of conelet abortion, morphologically characterized by a slight browning in the pith area of the conelet, ATP levels almost doubled. As the conelet became more necrotic, ATP levels dropped. Sausage casing, which was used to shield strobili during the pollination period, was found to have a greenhouse effect on the conelets, hastening their development. Both the ATP burst and the beginning of conelet abortion was 1–2 weeks earlier for the encased conelets.
Ardhachandra, a new genus of the Hyphomycetes
Authors: Subramanian C. V. , Sudha K.
Published: May 2008

A dematiaceous Hyphomycete collected on Ixora leaf litter from India is described. The fungus produces two types of conidia: lenticular and selenoid, both typically bivalved with a germ slit, blastic, solitary, terminal on the conidiophore and its successive sympodial proliferations. It is conspecific with the Tanzanian collection of a fungus assigned by Pirozynski in 1972 to Rhinocladiella critaspora Matsushima and designated the holotype of a new species of Pseudobeltrania, P. selenoides, by de Hoog in 1977. Pseudobeltrania selenoides is made the type of a new genus Ardhachandra; Rhinocladiella critaspora Matsushima (= Pseudobeltrania critaspora (Matsushima) de Hoog) is transferred to Ardhachandra as A. critaspora (Matsushima) comb. nov.
Variation in the size of macropycnidiospores and pycnidia of Septoria tritici on wheat
Authors: Shearer B. L. , Wilcoxson Roy D.
Published: May 2008

Macropycnidiospores and pycnidia of Septoria tritici in leaves of naturally infected Cheyenne and Minter winter wheats decreased in size as the growing season progressed. The change in the size of the spores and pycnidia was negatively correlated with days after planting and increased leaf necrosis. In glasshouse experiments, the size of spores and pycnidia was not significantly affected by changes in the percentage of the leaf area that was covered by lesions bearing pycnidia, vernalization, or the isolate of S. tritici. Spores and pycnidia were significantly larger at 18 °C than at 27 °C in Era spring wheat but not in Minter winter wheat. In both Era and Minter, the spores that formed in infected leaves with dry surfaces were smaller than those that formed in leaves with wet surfaces, although the differences were not significant. Pycnidia in leaves of Era that were kept dry were significantly larger than those in leaves that were kept wet, but wet leaves senesced rapidly.
A downdraft field chamber for studying the effects of air pollutants on plants
Authors: Runeckles V. C. , Staley L. M. , Bulley N. R. , Black T. A.
Published: May 2008

A new type of field exposure chamber for air pollution studies is described and its performance is evaluated. The chamber is designed to provide a steady downward air flow over a 2.44-m-diameter plot, with air venting laterally at soil level. It consists of a filter box above a 0.92-m-diameter fan in a housing mounted atop a conical welded steel frame. The fan is located 4.9 m above soil level. The frame enlarges from a diameter of 1.22 m at the top to 2.44 m at the base and is enclosed within a 0.5-mm (20-mil) polyvinylchloride cover terminated 20 cm above soil level. Activated charcoal and dust filters above the fan reduce the levels of ambient pollutants, particularly particulates and oxidants. Pollutant gases to be studied are introduced immediately below the fan to ensure mixing.Measurements of air velocity and the concentration of introduced pollutants indicate uniform distribution with considerable turbulence, while net radiation and temperature measurements indicate a small greenhouse effect due to the presence of the superstructure. The performance of the chamber is compared with others in use under field conditions.
Ultrastructural changes in shoot apex cells of winter wheat seedlings during ice encasement
Authors: Pomeroy M. Keith , Andrews Chris J.
Published: May 2008

The decline in viability of cold-hardy Kharkov winter wheat (Triticum aestivum L.) seedlings during ice encasement at −1 °C was accompanied by characteristic ultrastructural changes. A dramatic increase in endoplasmic reticulum was observed within a few days. This proliferation of endoplasmic reticulum often resulted in the formation of an elaborate series of parallel membranes, either dispersed randomly throughout the cytoplasm or in the form of concentric whorls. However, the structural integrity of many cellular organelles was largely unaffected even by prolonged ice encasement resulting in death of the plants. In contrast, exposure of cold-hardy seedlings to near lethal, subfreezing temperature resulted in severe disorganization of cellular organelles. Ice encasement of nonhardened seedlings resulted in complete kill within 4 h. After 16 h ice encasement, occasional concentric whorls of endoplasmic reticulum and copious amounts of osmiophilic material were observed in the cytoplasm. Upon removal of the ice encasement stress, the accumulated endoplasmic reticulum disappeared rapidly during recovery at either2 or20 °C.
Chemotaxis of zoospores of Phytophthora megasperma to primary roots of alfalfa seedlings
Authors: Chi C. C. , Sabo F. E.
Published: May 2008

Chemotaxis of the zoospores of Phytophthora megasperma was studied on freshly excised primary root tips of 2-day-old seedlings of nine alfalfa (Medicago sativa L.) cultivars and four other legume species. The highly susceptible cultivars Saranac, Algonquin, and Vernal attracted masses of zoospores within minutes after being placed into fresh zoospore suspensions. The moderately susceptible cultivars Iroquois, Angus, and Thor displayed less severe en masse zoospore accumulation. Resistant cultivars Apollo, Agate, and to a lesser degree WL-318 exhibited minor chemotaxis.Zoospores were strongly attracted to the region of elongation, immediately above the root cap area. Relatively few zoospores, if any, were attracted to the root cap and older regions of the roots. Zoospores were not attracted to root hairs. Within 0.5-1 h, zoospores attracted to the roots began to encyst and germinate. Germ tubes always originated from the side of cysts closest to the root surface, and all showed unidirectional growth towards the root.Very weak or no chemotactic responses of zoospores to nonhost legume plants of white sweet clover (Melilotus alba Desr.), red clover (Trifolium pratense L.), bird's-foot trefoil (Lotus corniculatus L.), and soybean (Glycine max (L.) Merr. cv. Vansoy) were observed. Roots of susceptible alfalfa seedlings pretreated in boiling water did not attract zoospores.Injured, susceptible alfalfa roots displayed a strong preferential attraction around a wounded root area. Varying zoospore densities occurred at different distances from the wound. Wounded, resistant alfalfa roots showed slightly more zoospore accumulation than the uninjured resistant roots.The magnitude of chemotaxis and response time appear to be related to the susceptibility or resistance of the young, primary roots of alfalfa seedlings.
Contribution à l'étude écologique des dunes mobiles. II. Les conditions édaphiques
Authors: Lamoureux Gisèle , Grandtner Miroslav M.
Published: May 2008

The authors have studied and classified the soils of the nine phytosociological elements described in a previous article (Lamoureux, G., and M. M. Grandtner. 1977. Contribution à l'étude écologique des dunes mobiles. I. Les éléments phytosociologiques. Can. J. Bot. 55: 158–171). The results of the physicochemical analysis have been used to compare the soils of the different phytosociological elements statistically to characterize them and to find the factors which determine the distribution of the phytosociological elements on the mobile dune with ammophila. A number of pedogenetic trends could be recognized, but at the soil level, the passage from one phytosociological element to another is little marked.
Genetic and plastic responses in geographic differentiation of Bromus rubens populations
Authors: Wu K. K. , Jain S. K.
Published: May 2008

Populations of B. rubens were sampled in the northern and central Coastal Ranges and northern Central Valley of California to study the geographic variation patterns. Quantitative estimates of variation were obtained on plants collected in nature, and their progenies were grown under controlled environments. Discriminant function analysis was used to estimate the variation among populations in both natural and controlled environments for four quantitative characters. These variations appear approximately proportional to the geographical distances among localities and to the measures of genetic differentiation. It was found that for these four quantitative characters, about 12–27% of the total geographic variation among natural populations of B. rubens was contributed by genetic differentiation, while the rest (73–88%) was contributed by the so-called plastic response (nongenetic variation) to different local environments. This finding suggested that phenotypic plasticity is important for the wide adaptability of this species.The similarity between the dendrogram patterns of both genetic similarity and phenotypic similarity for esterases and quantitative characters, respectively, suggested that the observed variation may be adaptive and correlated with environmental components of climate and habitat diversity. Such comparisons of different character sets may provide a useful way of deriving the adaptive basis of geographic variation.
The taxonomy of the Ramalina siliquosa species aggregate (lichenized Ascomycetes)
Authors: Sheard J. W.
Published: May 2008

The taxonomy of this western European, maritime, cliff-inhabiting species complex has in recent years been based primarily on chemistry. Five of the species are characterized by a replacement series of medullary depsidones and a sixth is acid deficient. The taxonomy of this group has been reinvestigated using modern methods of thin-layer chromatography and numerical taxonomy based on individuals collected from three well separated regions in western Britain.The discovery that low concentrations of protocetraric acid usually accompany salazinic acid leads to the supposition that it may be a precursor compound in the same way that norstictic acid is widely accepted as being the precursor of stictic acid. The chemical structures of the compounds also support such a view. In addition, hypoprotocetraric acid is structurally very similar to protocetraric acid so that two biosynthetic pathways can be hypothesized for the group. These are as follows: (1) hypoprotocetraric → protocetraric → salazinic acid and (2) norstictic → stictic acid.Three types of numerical classification were undertaken to test for the presence of a correlation between morphological attributes (39) and chemical attributes (variable numbers). These are classifications in which (1) chemical attributes were excluded. (2) medullary constituents were given equal weight, and (3) putative biosynthetic pathways were given greater weight than their constituent substances. The three methods each produced two virtually identical clusters corresponding to individuals possessing one or other of the two biosynthetic pathways, a result which established a close correlation between morphology and chemistry within the group. Cophenetic correlation coefficients between the classifications were in excess of r = 0.900. Acid-deficient individuals were found associated with both clusters.Comparison of the within- and between-group sums of squares showed that the two clusters represent taxa which in view of the strong correlation between morphology and biosynthetic pathways, should be recognized at the species level. Principal components analysis of a data set derived from that used in type 3 classification also produced the same two clusters. This analysis also yielded two subgroups within each cluster which are to be the subject of further studies. The correct names for the two species corresponding to individuals with the salazinic and stictic acid pathways are Ramalina siliquosa (Huds.) A.L.Sm. and R. cuspidata (Ach.) Nyl., respectively.
Rod-shaped and spherical viruslike particles in cowpea rust fungus
Authors: McDonald John G. , Heath Michèle C.
Published: May 2008

Three types of rod-shaped viruslike particles (VLPs) (a short rigid rod (RR), 260 × 12 nm. a long narrow-diameter flexuous rod (NFR), 660 × 10 nm, and a long wide-diameter flexuous rod (WFR), 740 × 16 nm) and a spherical VLP (35 nm in diameter) were found in extracts of uredospores, germ tubes, and pustules of cowpea rust, negatively stained with ammonium molybdate. Both the size distributions and the stability of these VLPs was affected by the choice of stain since when phosphotungstic acid was used, two additional length classes of the RR (150 nm and 90 nm) were noted, and this stain tended to disassemble the WFR by unwinding the helix of this particle. The WFR also disassembled at pHs 4and5 in 10 mM acetate but only at pH 4 in the presence of 0.2 M NaCl. Examination of cowpea rust by thin sectioning revealed the presence of four types of VLPs. Morphologies of these particle types were consistent with the data obtained by negative staining.
Image-analyzing computer in plant science: more and larger vascular rays in sugar maples of high sap and sugar yield
Authors: Morselli Mariafranca , Marvin James W. , Laing Frederick M.
Published: May 2008

The total area and number of xylem rays and vessels from tangential and cross sections of twigs of 12 sugar maples (Acer saccharum Marsh.) were determined by the use of an image-analyzing computer. A nested analysis of variance indicated that xylem rays of trees of high sap and sugar yield are more numerous and larger than the rays of other sugar maples. The total area and number of xylem vessels were about the same in all 12 trees.
Populus in late-Pleistocene pollen spectra
Authors: Mott R. J.
Published: May 2008

Populus profiles in pollen diagrams have often been ignored or given little attention because of problems with identification and preservation. Modern surface spectra aid in the interpretation of fossil assemblages, but exact modern analogues have not been found. Recent studies from several localities in Canada have revealed peaks in Populus pollen in late-Pleistocene and (or) early-Holocene spectra, and relative and absolute frequencies indicate that Populus may have played a significant role in the transition from tundra to forested conditions.
Spore development and germination in Cinclidium (Mniaceae, Bryophyta), with special reference to spore mortality and false anisospory
Authors: Mogensen Gert Steen
Published: May 2008

Spores of Cinclidium arclicum (B.S.G.) Schimp., C. stygimn Sw., and C. subrotundum Lindb. pass through five phases of development from meiosis to protonema formation: tetrad phase, perine formation phase, stationary phase, swollen phase, and distension phase. They are shed from the sporangium at the termination of the swollen phase and show all characters diagnostic to the first phase of germination of spores of Funaria hygrometrica and Ceratodon purpureus. At the swollen phase, and as a contrast to spores at the three first phases of the sporogenesis, the spores of Cinclidium behave like a population of unicellular plants which grow under conditions with still decreasing quantities of liquid available for continued expansion.In Cinclidium, spore mortality occurs during the stationary phase, but otherwise, lethal factors appear to be independent of general spore development. For Cinclidium arcticum and C. stygium, spore mortalities of 50% generally occur, which can be explained by a genetic system based on the presence of two differentiating genes, each of which consists of a dominant and a recessive allele.False anisospory, here proposed as a new term, is present in a sporangium when the spore mass consists of both smaller dead spores and relatively larger living spores. It occurs in the three species of Cinclidium studied. False anisospory is caused by the death of a fraction of the spore mass during an intermediate stage of sporogenesis and the maturation of the remaining fraction to the subsequent swollen stage.It is probable that one of the two differentiating genes responsible for the false anisospory and the 50% spore mortality in Cinclidium arcticum and C. stygium is located in the sex chromosome, while the other gene is located in one of the autosomes. Since Cinclidium arcticum, n = x = 7, is dioecious and C. stygium, n = 2x = 14, is monoecious, false anisospory is independent of sexuality and the level of ploidy.
Evidence for Picea pungens in north-central Montana and its significance
Authors: Strong W. L.
Published: May 2008

The analysis of Picea cone scales from the Sweetgrass Hills of Montana substantiates the existence of Picea pungens Engelm. in north-central Montana. These results extend the geographical range of P. pungens and identify a new native species within the state of Montana.
Zingiberopsis, a fossil genus of the ginger family from Late Cretaceous to early Eocene sediments of Western Interior North America
Authors: Hickey Leo J. , Peterson Rayma Kempinsky
Published: May 2008

Zingiberopsis attenuata Hickey and Peterson is a new species of monocotyledon from the Paleocene Paskapoo Formation of Alberta. Leaves of this species with their parallel veins grouped into three size sets are intermediate between the Late Cretaceous Zingiberopsis magnifolia (Knowlton) Hickey, new combination, with four discrete sets and Zingiberopsis isonervosa Hickey, of late Paleocene and early Eocene age, with only one set. Zingiberopsis has large, elliptic to ovate leaves with a costa composed of a number of concurrent strands, a set of parallel veins emerging at low angles from the costa, and relatively distantly spaced transverse veins running between adjacent parallel veins. Morphology of the genus matches that of Alpinia in the Zingiberaceae except for greater irregularity of the parallel vein set at and near their origin on the costa and the lack of any evidence of a ligule on the petiole as in Alpinia. Species of Zingiberopsis demonstrate a clear trend toward loss of the wider parallel vein subsets over the approximately 20-million-year range of the genus. In addition, the overlooked character of the arrangement of the parallel vein subsets across the width of the leaf may have potential in the taxonomic determination of monocotyledonous leaves.
Dynamics of the boreal forest south of James Bay
Authors: Carleton T. J. , Maycock P. F.
Published: May 2008

Ordination models of approximate environmental and dynamic relationship between eight boreal tree species were constructed based upon principal components analysis and Kruskal's nonmetric multidimensional scaling. The assumptions inherent in these models are stated and discussed. The data consisted of 152 forest stands from the closed-crown boreal forest zone of Ontario and Quebec south of James Bay. Sequential forest succession, as demonstrated by similar techniques for a section of the Wisconsin evergreen–hardwood forest, is not common in the region of boreal forest studied. However, for those species in common between this and the Wisconsin study, similar dynamic pathways are indicated despite differences in sample size and field technique. Tree species developmental pathways, as indicated by 'succession vectors' on the ordination models are, for the most part, short and circular with the exception of Abies balsamea (balsam fir). This reflects the reestablishment of similar, relatively monospecific forest stands following catastrophic forest destruction by fire and (or) other agencies. Where catastrophe does not intervene, deciduous primary forest species may be succeeded by an understory of A. balsamea or by Picea mariana (black spruce). Equally, some forest stands of primary establishment may become decadent with little or no subsequent tree growth. These observations are discussed with respect to the general notion of forest succession.
Factors influencing the distribution of Egregia menziesii (Phaeophyta, Laminariales) in British Columbia, Canada
Authors: Gordon D. K. , Wreede R. E. DE
Published: May 2008

Egregia menziesii (Turner) Areschoug is a common component of the algal flora along the west coast of Vancouver Island, Queen Charlotte Strait, and the Strait of Juan de Fuca but is absent from the Strait of Georgia in British Columbia, Canada. This distribution pattern was found to be correlated with temperature and salinity in that E. menziesii is not present in areas where there are seasonal periods of low salinity and high temperature. To test this correlation, field transplants of sporophytes and laboratory experiments with sporophytes and culture work were carried out. The results suggest that the distribution of E. menziesii is limited by specific combinations of salinity and temperature; it requires high salinities and temperatures less than 15 °C for its survival.
Fine structure of shiitake, Lentinus edodes. VI. Cytoplasmic microtubules in relation to nuclear movement
Authors: Nakai Y. , Ushiyama R.
Published: May 2008

In the course of electron microscopic observations on basidiosporogenesis of Lentinus edodes (Berk.) Sing., the cytoplasmic microtubules, which are about 24 nm in diameter and associate closely with the postmeiotic nuclei, were observed to be common during movement of nuclei from a basidium into the respective basidiospores through sterigmata. These microtubules orient striately from the spindle-pole body (SPB), situated at the leading portion of a migrating nucleus, into the cytoplasm of a nearly mature basidiospore and appear to precede the migrating nucleus. The association of microtubules radiating from the SPB with the interior of a migrating nucleus was particularly indicated as being a characteristic event observed during nuclear movement of L. edodes. After completion of nuclear movement, these microtubules disappear completely. It is suggested that the microtubules associated with SPB may play an essential role in nuclear movement from the basidium to the basidiospore.
A reinvestigation of sporulation in the plasmodial slime mold Echinostelium minutum
Authors: Haskins E. F.
Published: May 2008

A protoplasmodium of Echinostelium minutum de Bary forms a single fruiting body consisting of a globose mass of whitish spores mounted at the apex of a tapering acellular stalk within 24 to 48 h of the time that it is deprived of a microbial food supply. Sporulation is normally completed within [Formula: see text]. Phase-contrast microscopy indicates that a single, synchronous, intranuclear division occurs during the progressive, centripetal cleavage of the sporangium. This contention is supported by the observation that the number of uninucleate protospores is invariably twice the number of dividing nuclei present in the immature sporangium. Binucleate protospores are occasionally formed by the incorporation of nondividing, pycnotic nuclei.
The cytogeography of Aster pilosus (Compositae): Ontario and the adjacent United States
Authors: Semple John C.
Published: May 2008

The chromosome numbers of individuals from 48 sites in southern Ontario and 12 sites in the eastern U.S.A. were determined. Twenty-one populations in Ontario of Aster pilosus var. pringlei were found to be hexaploid with 2n = 48 (first report for taxon). Sixteen populations of Aster pilosus var. pilosus were tetraploid 2n = 32 (first report for this ploidy level) and 11 populations were hexaploid 2n = 48. In southwestern Ontario, hexaploids of var. pilosus were found concentrated in one region on glacial sand, till soils, and coarse gravel fill, while tetraploids were only found on finer textured silt plains and limestone outcropping. In Ontario, the two varieties are nearly allopatric, only growing in close proximity on Presqu'ile Point on Lake Ontario. Both tetraploid and hexaploid plants of var. pilosus were found in the United States. The hexaploids were common near the Great Lakes but rare further south. Aster pilosus var. demotus was treated as a synonym of var. pilosus, since nearly glabrous plants produced pilose shoots when transplanted to the greenhouse at the University of Waterloo.
Pollen dimorphism in Silene alba (Caryophyllaceae)
Authors: McNeill J. , Crompton C. W.
Published: May 2008

Male plants of Silene alba are found to possess one of two pollen types, distinguished by the ektexine structure. In one type, found in 58% of the plants examined, the ektexine is punctate with spinulose and tubuliferous elements, whereas the other type has a reticulate–spinulose ektexine. Associated with the ektexine features are differences in grain diameter, wall thickness, and pore number. In the related species S. noctiflora and S. dioica, all of the pollen examined had a reticulate–spinulose ektexine. No evidence could be found for the possibility that the reticulate ektexine in S. alba might be due to introgression from S. dioica. Pollen dimorphism has not hitherto been reported in the Caryophyllales (Centrospermae), nor has it previously been established in a dioecious species. This appears also to be the first report of genetically controlled pollen dimorphism in a species that does not exhibit heterostyly.
Nutrient leakage from dried and rewetted conidia of Alternaria brassicae and its effect on the mycoparasite Nectria inventa
Authors: Tsuneda A. , Skoropad W. P.
Published: May 2008

Conidia of Alternaria brassicae leaked various amino acids and sugars when they were exposed to an alternate dry–wet condition; the longer the drying period, the larger the amount of leakage. Among the amino acids, glutamine was exuded in the largest amount, followed by aspartic acid and glutamic acid. The sugar fraction consisted mainly of glucose and fructose. These leaked nutrients stimulated germination and growth of the mycoparasite of A. brassicae, Nectria inventa. As a result, the germination rate of Alternaria conidia was drastically reduced to less than 5% and they were eventually destroyed by N. inventa. In the absence of N. inventa, however, conidia of A. brassicae germinated at the rate of 93.7% after being dried for 12 h at 32% RH.
Amino acid metabolism in developing soybeans (Glycine max): glutamate synthase in the cotyledons
Authors: Storey Richard , Reporter Minocher
Published: May 2008

Extracts of developing soybean (Glycine max (L.) Merr.) cotyledons contained glutamate synthase activity (EC 2.6.1.53). The enzyme apparently was soluble and could be separated from glutamate dehydrogenase and NADH oxidase. Optimal synthase activity was at pH 7.8 in phosphate buffer. The enzyme was specific for L-glutamine as nitrogen donor and α-ketoglutarate as nitrogen acceptor. Activity was much greater with NADH than NADPH as reductant and evidence was obtained which indicated that the latter activity was an artifact in the in vitro assay owing to the presence of pyridine nucleotide phosphatase activity. Synthase activity was not reversible but was influenced by the addition of NAD+ to the reaction mixture. The synthesis of [14C] glutamate by crude extracts was also detected with ferredoxin as electron donor. The role of glutamate synthase in providing α-amino N for amino acid synthesis in the developing legume seed was further clarified.Glutamate dehydrogenase (EC 1.4.1.3) activity was also measured in the cotyledons and its possible role in NH4+ metabolism was discussed.
Pollen morphology of some western Canadian Myriophyllum species in relation to taxonomy
Authors: Mathewes Rolf W.
Published: May 2008

The pollen morphology of four species of Myriophyllum from northwestern North American populations is described from studies using bright-field, interference-contrast, and scanning electron microscopy. Results indicate that M. verticillatum, M. heterophyllum, and M. hippuroides can be determined to species on the basis of pollen morphology. Myriophyllum spicatum and M. exalbescens are not readily separated on pollen morphology, although two tentative differences are suggested for further testing. It is also concluded that M. verticillatum should be recognized as a species clearly distinct from M. spicatum.
Taxonomic note: Lejeunecysta nom. nov. pro. Lejeunia Gerlach 1961 emend. Lentin and Williams 1976—dinoflagellate cyst genus
Authors: Artzner Darrah G. , Dörhöfer Gunter
Published: May 2008

The name Lejeunecysta is proposed for the dinoflagellate cyst genus Lejeunia Gerlach 1961 emend. Lentin and Williams 1976, a later homonym of the modern liverwort genus Lejeunea Libert 1820. Species of the genus are transferred accordingly.
The ultrastructure of the R.S. zoospore of the Chytridiomycete Physoderma gerhardti
Authors: Lowry Robert J. , Sparrow Frederick K.
Published: May 2008

The fine structure of the zoospore of Physoderma gerhardti Schroeter is described. It possesses a single very large lipid body (sometimes accompanied by several smaller ones) situated laterally to the nuclear cap – nucleus complex and is associated with electron-dense material (the microbody) and the single large posteriorly located mitochondrion. The single posterior flagellum proximally terminates in a kinetosome just short of the posterior cone-shaped end of the nucleus. The kinetosome lies in a deep groove in the mitochondrion and is associated with this organelle by striated rootlets. The kinetosome terminates in electron-dense material from which an array of microtubules arises. These microtubules run along the sides of the cone-shaped nucleus and nuclear cap. There is an accessory centriole lying close to and more or less parallel with the kinetosome. The cytoplasm contains a small amount of smooth endoplasmic reticulum and several inclusion bodies in the anterior region and several small vacuoles in the posterior region of the cell. The general internal organization of the zoospore of Physoderma gerhardti more nearly resembles that of a blastocladiaceous fungus than of any chytrid thus far investigated.
The genetics and evolution of gynodioecy in Nemophila menziesii (Hydrophyllaceae)
Authors: Ganders Fred R.
Published: May 2008

Nemophila menziesii typically bears perfect, protandrous. self-compatible but predominantly outcrossed flowers. In one population of Nemophila menziesii var. intermedia at Point Reyes, California, approximately 25% of the plants are completely male sterile. The flowers of these pistillate plants possess only small rudiments of stamens and lack anthers entirely. This phenotype is constant in nature as well as under cultivation. Male sterility appears to be inherited cytoplasmically, but there is at least one nuclear fertility-restoring allele in the population. The fertility-restoring allele may be at a single multiallelic locus, recessive to one nonfertility-restoring allele and dominant to another nonfertility-restoring allele, or there may be fertility-restoring alleles present at two or more loci. The population carries a significant load of deleterious recessive alleles at other loci, as evidenced by floral abnormalities and partial pollen abortion in some of the progeny from selfed hermaphrodites. Male sterility appears to be maintained in this population because the obligately outcrossed male steriles produce progeny which are more fit than the progeny produced from selfed hermaphrodites. Self-fertilization of hermaphrodites is probably higher in this population than in most populations of the species because the oligolectic-pollen-collecting bees, which are the normal pollinators of N. menziesii, are not present at this locality. Gynodioecy probably became selectively advantageous when the outcrossing ancestors of this population were subjected to drastic increases in the rate of self-fertilization owing to changes in pollinator fauna.
Seasonal changes in biomass, tissue chemistry, and net production of the evergreen hydrophyte, Lobelia dortmanna
Authors: Moeller Robert E.
Published: May 2008

The evergreen characteristic of Lobelia dortmanna L. involves biomass and nutrient conservation. Although 60% of the maximum, midsummer biomass overwinters, little or no new tissue is produced between October and early May. Annual net production, estimated from the rate of leaf turnover, is less than the maximum biomass (P/B = 0.69 per year). Nitrogen and P concentrations are lowest in mid-August, when the amount of each analyzed element per square metre is near its maximum (N, P, Ca, Mg, Na, K). Autumnal uptake of N may contribute 25% of the next season's growth requirements, but P uptake is largely offset by losses during the winter. Fruiting and sterile plants have similar contents of N, P, and K in late July, but the fruiting plants are richer in Ca, Mg, Na, Fe, Mn, and Zn. At the maximum depth limit of the population in Mirror Lake, New Hampshire (2.3 m), flowering is absent and seedlings are sparse, suggesting reproductive failure as a controlling factor at the margin of the population.