摘要:

Eleven plant sociations are reported from the McMurdo Sound region of continental Antarctica, and they are grouped in the Alga, Fruticose and Foliose Lichen; Crustaceous Lichen; and Short Moss Turf and Cushion subformations of the Antarctic Non-vascular Cryptogam Tundra formation. Their inclusion necessitated only minor modification of a vegetation classification developed in the maritime Antarctic.The most widespread vegetation consisted of sparsely developed communities of turf- and cushion-forming mosses in habitats ranging from dry cinder slopes to sand and gravel in seepage areas and by meltwater streams. The bryophyte colonies seldom exceeded 4 cm in depth, and although total plant cover within the communities locally reached 85%, it was more frequently under 5%. TheSarconeunimassociation appeared to tolerate more arid conditions than theBryumassociation, whose communities occasionally merged with algal sociations occupying certain of the streams. Exposed rock habitats normally supported at most small scattered thalli of crustaceous lichens, well-developed lichen communities being rare.

ISSN:0008-4026    

DOI:10.1139/b73-302

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Abundant added material and use of phase-contrast microscopy show thatPuccinia heucherae, P. austroberingiana, andP. saxifragaeare separate species and that each is divisible into two or more populations. Described as new areP. haraeonChrysosplenium, axillare;P. saxifragae-geionSaxifraga geum;P. heuchereavars.meridionalis, minor, cordillerana, diffusistriata, andjaponicanew vars., and var.saxifragae-micranthae(Barclay) new comb.;P. austroberingianassp.saxifragarum;P. saxifragaevar.curtipes(Howe) Diet., vars.longior, heucherarum, holochloaeandmitellaenew vars.;P. pazschkeivar.ferrugineaenew var. New host records, correction of erroneous host records, and new biogeographic data throw additional light on the radiation ofSaxifragaand emphasize a few erroneous assignments of species to sections or subsections.

ISSN:0008-4026    

DOI:10.1139/b73-303

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The life history ofP. linearisGrev. in nature was studied for 2 years at Sandy Cove, Halifax County, Nova Scotia, Conchospores of this winter alga were present in the supralittoral zone as early as August, although thalli were not visually apparent until mid-October to late October. The first major deposition of conchospores coincided approximately with decreasing sea temperature at 13–14 °C. Spores were deposited throughout the winter until March, when sporulation presumably declined and few new thalli appeared on the study site. A few conchospores were retrieved from the supralittoral zone in April, when extant thalli were bleached or moribund, and as late as June, after the population had died. Conchocelis ofP. lineariswas not found in the supralittoral habitat of the leafy phase, but several specimens were located at a depth of 9 m in the sublittoral zone near the study site. Leafy thalli became fertile 3–5 weeks after their appearance on the site, and were largely dioecious; broader thalli in the upper littoral zone were frequently monoecious, and displayed α- and β-spores simultaneously. Development of the population was enhanced by thin films of moisture but not by standing water such as tide pools; nor did youngP. linearisthrive inUlothrix flacca–Urospora penicilliformisassociations. Death of leafy thalli in spring appeared to result from an interaction of increasing temperature and photoperiod. Alternation of the leafy phase with conchoecelis is obligatory inP. linearis; vegetative reproduction by neutral spores was not observed, and thalli did not perennate via the remnants of basal portions which sometimes persisted through the summer. Intergradation ofP. lineariswithP. umbilicalisis discussed.

ISSN:0008-4026    

DOI:10.1139/b73-304

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The ultrastructure of epicuticular glume waxes in two tetraploidAvenaspecies,A. magnaandA. murphyi, and in one hexaploid species,A. sterilis, has been studied and documented with the aid of the scanning electron microscope (SEM). The usefulness of this approach for taxonomy and diagnostic purposes has been evaluated, and the specific configurations of those epicuticular waxes compared in relation to the genomes.

ISSN:0008-4026    

DOI:10.1139/b73-305

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Interfertility tests between Alberta collections identified asCoriolus hirsutus, C. pubescens, C. velutinus, C. zonatus, andC. versicolorhave shown that there are only two distinct species of this complex in Alberta, each with a range of morphological variation. Both these species, which are being calledCoriolus hirsutusandC. pubescens, have the tetrapolar type of fertility. Isolates of basidiocarps from Sweden identified asCoriolus hirsutuswere intersterile with Alberta isolates of this species, which suggests the existence of two different species. Cultures ofC. versicolor(Ontario) were unilaterally dikaryotized byC. hirsutusand to a lesser extent byC. pubescens, indicating very close relationship. Dark pigment lines frequently formed between paired isolates of both distantly related and closely related cultures, indicating that it is not mating-type factors which control pigment formation in the contact zone.

ISSN:0008-4026    

DOI:10.1139/b73-306

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The closely related generaRhynchosiaandEriosemahave tricolporate pollen. Twenty-two species ofRhynchosiaand nine species ofEriosemawere examined with the light microscope. Most of the species have isopolar-type grains, but 11 species have the hitherto rarely described heteropolar-type pollen, i.e. on a single grain, the ends of the colpi subtend a greater area at one pole than at the opposite pole. Duplicate examination of 13 species indicates that polarity types are constant within those species. While the genera cannot be separated on the basis of pollen morphology alone, there are some pollen characters which embrace most species in any one genus.Eriosemaspecies are mostly heteropolar (67%) andRhynchosiaare predominantly isopolar (77%). The lumina of the reticulum ofRhynchosiatend to be smaller than those ofEriosemaand, with one exception, the muri ofEriosemahave acute tops while those ofRhynchosiaare obtuse. Scanning electron micrographs illustrate pollen morphology.

ISSN:0008-4026    

DOI:10.1139/b73-307

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Asymptotic increases in diversity, richness, and evenness are reported from a primary sand dune succession. Rapid increases in diversity and evenness were observed in the first 1000 years of the 4800 sampled; richness appears to increase little after 2000 years of succession.

ISSN:0008-4026    

DOI:10.1139/b73-308

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Freeze-etching has revealed changes in the orientation of rodlet fascicles on the surface of the outer wall layer of conidia and conidiogenous cells at successive stages of development. Specific patterns of rodlet fascicles reflect the progressive increase in cell volume and change in shape characteristic of 'blastic' conidium development inGonatobotryum apiculatum. Rodlet patterns over most of the wall surface of conidia ofOidiodendron truncatumandGeotrichum candidum, on the other hand, are not significantly different from the patterns of rodlet fascicles on the wall of the determinate, fertile hyphae from which the conidia arose. This latter structural–developmental relationship is suggested to be characteristic of the 'arthric' mode of conidiogenesis. It is demonstrated, however, that conidium formation inOidiodendron truncatumdoes involve some meristematic activity in addition to conversion and disarticulation of pre-existing hyphal elements. A diagrammatic interpretation of these changes in rodlet patterns during conidiogenesis is presented.

ISSN:0008-4026    

DOI:10.1139/b73-309

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Sequential quantitative analyses of phaseollin associated with individual sites of infection byColletotrichum lindemuthianumon etiolated hypocotyls ofPhaseolus vulgarisprovide further insight concerning the possible function of phaseollin in compatible and incompatible host response. When detected, phaseollin was localized in and (or) around individual infection sites; it was not detected in adjacent healthy tissue. Its occurrence was correlated with the time of appearance of visible, necrotic flecks at sites of incompatible response. It was not detected at visibly necrotic sites of compatible response until these became delimited in appearance, after which it occurred in large amounts. Delimitation at these sites occurred well after visible necrosis was first apparent. At high levels of infection, individual sites of compatible infection coalesced before delimitation, and in such instances phaseollin was virtually absent for the duration of the experiments. The levels of phaseollin occurring at individual infection sites indicate that it does not function as the primary determinant of interaction type, but is associated with delimitation at sites of both compatible and incompatible interaction. With respect to phaseollin production, the difference between these interactions was clearly one of time of occurrence, rather than amount produced.

ISSN:0008-4026    

DOI:10.1139/b73-310

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Twenty-four morphological characters of native ManitobaPopuluswere studied in an attempt to delineate species and variants and provide keys for correct identification. The results support the hypothesis that the variants have originated from intersectional hybridization ofP. balsamiferaL. (sectionTacamahacaSpach.) andP. deltoidesMarsh. var.occidentalisRydb. (sectionAegeirosDuby).Populus×jackiiSarg. encompasses the collective group of individuals resulting from this hybrid cross. The hybrid individuals are widely distributed and occur commonly where the two parental species are growing together.

ISSN:0008-4026    

DOI:10.1139/b73-311

出版商:NRC Research Press    

年代:1973

数据来源: NRC