摘要:

Descriptions of 24 species of cryophylous algae and 3 species of microfungi are given. Ten of these algae are new records for the algal flora of continental North America. The organisms grouped in the speciesChlamydomonas nivaliswere found to be by far the most common member of the red snow flora, being found in every area of the Pacific Northwest from which collections were made. Green snow is described from the Olympic National Park, having as its causative agent eitherChlamydomonas yellowstonensis,or other snow algae which had lost the characteristic masking (red‐to‐yellow pigmentation) as a result of the population developing in shade. Other members of the snow's flora included species of the following genera:Scotiella, Chodatella, Raphidonema, Tetraëdron, Mycanthococcus, Stichococcus, Chlorosphaera, Protococcus, GloeotheceandRomeria.The 3 fungi identified are:Selenotila nivalis, Chionaster nivalisandChionaster bicornis.Kol's silicotrophic‐calcitrophic theory which relates the red and green snow vegetation types to the underlying rock composition is evaluated, and it is concluded that there is no sound reason for this correlation. It is suggested that the degree of illumination is a more important factor in determining the distribution of these pigmented organisms.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06750.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Hildenbrandia rivulariswas collected in Denmark and the United States. The life history of this encrusting red alga is described on the basis of unialgal cultures maintained for more than 2 years. Significant changes in cellular and colonial morphology are reported. Events of the life history (i.e., reproduction by stolons, fragmentation, or gemmae; and manner of branching) which were previously in question or unknown are clarified. Mechanism(s) of certain morphogenetic phenomena remain obscure (cell wall and plastid ontogeny). These and related problems are now under investigation.Hildenbrandiashould be added to the freshwater algal flora of the United States.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06751.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Myxomycete plasmodia of 4 types (other thanPhysarum polycephalum), namely,Didymium clavus, Hemitrichia vesparium, Stemonitis fusca,andClastoderma debaryanum,were sectioned and studied by electron microscopy. Organelles of all species have been described. In general, they are similar in the various species studied and resemble those found in animal cells and the cells of some lower plants. Mitotic figures and centrioles were not observed. Fibrils of 3 types were found; they were most prominent inClastoderma debaryanum.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06752.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The glass‐slide technique was used in a 14‐week study to show the effects of 4 concentrations of zinc on periphytic communities in 4 outdoor canals supplied with running pond water containing its natural biota. No species was found that could be considered an indicator of zinc. The effect of adding 1 mg/liter or more of zinc was to reduce the number of dominant species. A geometric regression of the average number of dominant algal species was found beginning with the control, with no added zinc, and proceeding from that to the largest concentration of zinc. A relatively large concentration of zinc resulted in comparatively low biotic diversity. Fungi and slime‐forming bacteria produced a large standing crop in the largest zinc concentration, apparently by digesting the killed incoming phytoplankters that were used as their food.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06753.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Interpretation of thePotamogetonflower is complicated by the attachment of the “perianth segment” to the stamen connective. Developmental studies show that the perianth segments arenotoutgrowths of the stamen connectives. They are initiated on the floral apex acropetally before the (superposed) primordia of the stamens. After the inception of the stamen primordia, growth occurs in the regions between the primordia of each perianth segment and stamen. Thereby the bases of the developing perianth segment and stamen become united, and in the adult flower eventually the perianth segment is inserted on the connective of the stamen. The primordium of the perianth segment develops from the 2 outer layers (tunica) of the floral apex, in contrast to the stamen primordium which originates from the 3 outer layers. The vascular bundles for each perianth segment–stamen region develop acropetally from 1 common bundle which bifurcates into 1 bundle for the perianth segment and 1 for the stamen. The bundle leading into the perianth segment branches in a more or less dichotomous manner. The veins form none or only 1 or 2 anastomoses at the base of the lamina, whereas the vein endings remain free. The interpretation of the perianth segments is discussed in terms of the classical and the gonophyll theory. Since both theories rest on an ambiguous methodological basis, interpretation is postponed until a new approach to comparative morphology has been worked out and until the floral development of other Helobiales has been studied.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06754.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The following mistletoes and their hosts were studied:Phoradendron serotinum(Raf.) M. C. Johnst. (P. flavescens[Pursh] Nutt. var.macrophyllumEngelm.) onJuglans hindsiiJeps. (California black walnut),Arceuthobium campylopodumEngelmn. f.abietinum(Engelm.) Gill onAbies concolor(Gord. and Glend.) Lindl. (white fir) andA. magnificaA. Murr (red fir),Arceuthobium campylopodumEngelm. f.campylopodum(Engelm.) Gill onPinus sabinianaDougl. (Digger pine), andAmyema pendula(Spleng) Tiegh. onEucalyptus macrorhynchaF. Muell. ex Benth. (stringybark). With the exception of theAmyemaleaves, the mistletoes are richer in free and bound amino acids than their hosts; moreover, their amino acid composition closely resembles that of their hosts. Nevertheless, there is no satisfactory evidence that mistletoe specificity depends on the amino acid composition of the hosts. Some mistletoes contain γ‐aminobutyric acid and asparagine, not found in all hosts. All the above mistletoes but no hosts contain free hydroxyproline. These results are discussed in relation to (1) the region in the mistletoes where hydroxyproline is formed and (2) the possibility of using certain amino acid analogs as selective poisons for mistletoes.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06755.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The carpels ofChamaemeles, Cotoneaster, Dichotomanthes,andPyracanthatend to be separate from one another, their sutures tend to be closed, and they become more or less bony at maturity. However, aside from having collaterally placed ovules, they do not appear to be structurally similar. There seem to be 2 different evolutionary trends in the ovular bundle–wing bundle relationship: inPyracantha,progressive fusion between the ovular bundle and the wing bundle has led to the formation of a “ventral” bundle; inCotoneaster,and possiblyChamaemeles,the wing bundle has become reduced and rather attenuated. A primitive pomoid state may be represented by the carpel ofDichotomanthes,which is completely free of the floral cup and in which wing and ovular bundles are separate. Differences in sutural closure appear only inCotoneaster,and in species of that genus the wing bundles and ovular bundles tend to be fused if the suture is closed, and separate if it is open.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06756.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

Ecotypic differentiation in transplanted clones ofAndropogon scopariusMichx.,A. gerardiVitman,Panicum virgatumL. andSorghastrum nutans(L.) Nash showed north‐south correlations. In Austin, Texas, during 1959–1962, southern populations had earliest spring activity, latest flowering and latest dormancy. Northern community fractions from Massachusetts to North Dakota showed early flowering and a short span separating initial anthesis among the species‐populations. Community fractions from Virginia to Nebraska had initial anthesis over a longer period than in more northern or more southern samples. Community fractions from South Carolina to eastern Texas had late flowering over a short period. Western community fractions, latitudinally and altitudinally diverse, were behaviorally uniform. The length of the growing period and its recurrent selection have sorted out ecological variants in harmony with the habitat gradients. Whether they are of the predominant physiognomic types, as in the true prairie region, or understory plants in the pine forests, the 4 grass taxa are in the climax matrix.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06757.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The transfer of energy to and from a Ponderosa pine branch involves solar radiation, thermal radiation from the ground, atmosphere, and surroundings, thermal emission by the branch, and free convection in still air and forced convection in wind. It is necessary to know the actual surface area of the branch, the effective area for absorbing sunlight, the effective area for absorbing long wave thermal radiation and for emission, and the free and forced convection coefficients. These parameters were determined using a solid silver casting of a Ponderosa pine branch suspended in an evacuated radiation chamber and in a wind tunnel. The actual surface area of the branch was determined by means of an electrolytic technique. Numerical examples are given of the evaluation of the temperature of a live branch based on energy transfer considerations. Comparison is made to our earlier work on spruce and fir.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06758.x

出版商:Wiley    

年代:1965

数据来源: WILEY

摘要:

The object of this investigation was to discover whether heterokaryosis and parasexuality occur in the imperfect fungusAscochyta imperfecta.Both phenomena have been observed. The wild type ofA. imperfectagrows on a minimal medium containing only salts plus a carbon source. Auxotrophic and morphological mutants have been isolated after treatment with ultraviolet light. When 2 different mutant auxotrophs are inoculated together onto minimal medium, colonies are consistently formed. These colonies might be due, a priori, to back‐mutation, diploidy, syntrophism or heterokaryosis. Back‐mutation and diploidy have been eliminated, since no back‐mutant nuclei have been isolated from any heterokaryon, and since the frequency of diploid nuclei is very low. The combination is primarily syntrophic (only 2% heterokaryotic hyphal tips) when the nicotinamide mutant is one component. The combination is primarily heterokaryotic (over 50% heterokaryotic hyphal tips) when both components are auxotrophs for amino acids. From the heterokaryotic hyphal tips, the 2 unaltered nuclear components have been isolated. Heterozygous diploid nuclei (4.2 X 10−‐7per haploid nucleus) can be isolated from heterokaryons by plating, onto minimal medium, the primarily uninucleate conidia from a heterokaryon of 2 auxotrophs. The resulting colonies are isolated as potential diploids. Three properties of these isolates establish their diploid nature: (1) the isolates are wild type for nutrition and morphology; (2) their conidial length is uniformly greater than that of the haploids (1.21 times); (3) the isolates produce segregants with nonparental combinations of the marker genes. The diploid isolates are much more stable than heterokaryons. The recombinants from the diploids are still diploid, since (1) their conidial length falls in the diploid range, and (2) one of the recombinants has segregated a second‐order recombinant. Many of the expected classes of recombinants have not been detected.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1965.tb06759.x

出版商:Wiley    

年代:1965

数据来源: WILEY