摘要:

This is a review of the discovery, characteristics and phylogenetic importance of the Progymnospermopsida. The origin of this group from the Devonian Rhyniopsida is briefly discussed as is the evidence that supports the relationship between the two principal orders, the Aneurophytales and Archaeopteridales. Differing interpretations about the origins of cycadophytes and coniferophytes from progymnosperms also are presented. It is recommended that the old class Gymnospermae be reinstated as a natural unit of vascular plant classification for those seed plants whose origins are with the Progymnospermopsida.

ISSN:0008-4026    

DOI:10.1139/b81-212

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Carex aphanolepisFr. & Sav. infected with uredinial and telial stages ofPucciniasp. was found to occur nearAecidium-infectedViola grypocerasA. Gray andV.yezoensisMaxim. Reciprocal inoculations with basidiospores and aeciospores onto nine species ofViolaandC.aphanolepis, respectively, showed the genetic relation between these different spore stages. This is the first caricicolous rust fungus which has an aecial stage onViola, and is described as a new species;Puccinia pulchellaOno & Kakishima.

ISSN:0008-4026    

DOI:10.1139/b81-213

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

A transmission electron microscopic study of nodules ofVicia fabahas demonstrated that rhizobia are released from the infection threads by an endocytotic process. The rhizobia escape from unwalled regions of the infection thread or unwalled droplets of thread matrix and upon escape are surrounded by a peribacteroid membrane which is derived from the plasma membrane bounding the unwalled regions of thread matrix. Thus, the release of bacteria inV.fabanodules is essentially identical to that reported in other leguminous nodules and the peribacteroid membrane does not arisede novoas previously reported by other workers.

ISSN:0008-4026    

DOI:10.1139/b81-214

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Numerical taxonomic analyses (particularly agglomerative clustering and ordination) were conducted on 55 species ofMedicago, using 75 mostly vegetative and fruiting characters. The material studied represents all conservatively accepted species of the genus, as well as 14 "problematical" species of which many are often considered to belong to the genusTrigonella, rather than toMedicago. Although the characters employed are substantially the same as those used by recent monographers who evaluated the genus by traditional subjective procedures, the present numerical examination suggests many relationships not previously appreciated.As a result of the analyses, it was judged appropriate to recognize 12 groupings. These are group 1:M.sativa(alfalfa) and 11 allied species; group 2:M.lupulinaandM.secundiflora; group 3: eight problematical species which have troubled taxonomists with respect to whether they should be placed inMedicagoorTrigonella; groups 4–8: each made up of a single divergent species, respectively:M.carstiensis,M.radiata,M.orbicularis,M.heyniana, andM.arborea; groups 9–12 four subgroupings of a larger group of 28 annual species. In the main, the composition of the seven polytypic groups is similar to those of taxa accepted by recent monographers, although some realignments of particular species are suggested by the present study. Groups 1 and 2 are much more similar to each other than indicated in recent treatments.Medicago arboreawas discovered to be much more dissimilar to all other species examined than thought previously.Medicago hybridaof group 1 was found to be a "master link" between species traditionally placed inMedicago, and many placed inTrigonella(group 3).The 12 groupings in turn fall into three assemblages that could be recognized as subgenera, or even as genera. These are A: groups 1, 2, 9, 10, 11, and 12; B: groups 3–7, inclusive; and C:M.arborea. Further research is suggested before formal categorization is undertaken.

ISSN:0008-4026    

DOI:10.1139/b81-215

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The legume tribe Trigonelleae comprisesMedicago(withM.arboreasometimes segregated as the monotypic genusRhodusia),Melilotus,Trigonella, and the monotypicFactorovskya. The wisdom of segregating the two monotypic genera may be questioned, and many species have been claimed to represent intergrading variation betweenMedicagoand eitherMelilotusorTrigonella, or between the latter pair. Previous morphological studies have not provided a satisfactory means of resolving generic delimitation in the Trigonelleae. In the present investigation numerical taxonomic analysis (agglomerative clustering and ordination) of floral characters indicated thatMedicago,Melilotus, andTrigonellacould be distinguished on the basis of combinations of floral attributes, although no single characteristic was capable of separating them completely.TrigonellasectionBuceratesproved to be quite distinctive from the remaining species ofTrigonellaexamined. Limited evidence was found for segregatingMedicago arboreaas a monotypic genus.Factorovskya aschersonianaproved distinctive, but its relationships remain enigmatic. Discriminant analysis was employed to test the affinities of "problematical" species allegedly intermediate betweenMedicago,Trigonella, andMelilotus. Most of the putatively intermediate species proved to be much closer to one of the genera than to the others. A syndrome of morphological features was discovered to separate the Trigonelleae into two classes of plants, the one group includingMedicago,Factorovskya, andTrigonellasectionBucerates, and the other comprisingMelilotusand the remaining examined species ofTrigonella. The former group contrasts with the latter by possessing interlocking wing and keel petals, relatively less apical fusion of the keel petals, and relatively well-developed wing petal horns; and by having a greater frequency of species with dilated filaments, with staminal tubes which are conical at the apex rather than blunt, and with standard petals having more than three clusters of veins. The latter three differences, however, are less frequent between the two groups than the first three. The floral syndrome could reflect adaptation of the former group of plants to outcrossing (perhaps relictual adaptation in the inbreeding species) by means of the "tripping" mechanism which is well-known inMedicago. If so, the taxonomic significance of the syndrome is difficult to ascertain, as it may have developed independently in the different genera in which it occurs.

ISSN:0008-4026    

DOI:10.1139/b81-216

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

The 18Fusariumspecies or varieties (F.acuminatum,F.anthophilum,F.avenaceum, var.avenaceum,F.culmorum,F.dimerumvar.dimerum,F.equisetivar.equiseti,F.graminearum,F.merismoidesvar.merismoides,F.nivalevar.nivaleand var.majus,F.oxysporumvar.oxysporum,F.poae,F.saccharivar.subglutinans,F.sambucinumvar.sambucinum,F.solanivar.solani,F.sporotrichoidesvar.sporotrichoides,F.tricinctum, andF.verticillioides) most frequently isolated from wheat are described and illustrated. The experimental conditions used in this study, such as medium, near ultraviolet irridiation at a wave-length of λ = 300–400 nm (black light), and temperature, cause some alteration of the morphology of some of the taxa to which plant pathologists are accustomed if the strains are grown on richer media and (or) without black light. This does not matter, however, because the method described here allows each species or variety to develop a unique and stable set of morphological features, which distinguishes it from all other taxa.

ISSN:0008-4026    

DOI:10.1139/b81-217

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Potebniamyces gallicolan.sp. is described from dwarf mistletoe galls (Arceuthobium tsugense(Rosendahl) G. N. Jones) on western hemlock (Tsuga heterophylla(Raf.) Sarg.), growing in British Columbia, Canada. It has a typicalPhacidiopycnisanamorph which is produced both in the host and in culture, as well as hyphal "bud" conidia produced in fresh agar cultures.

ISSN:0008-4026    

DOI:10.1139/b81-218

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Morphology and development ofHyalopycnis blepharistoma(Berk.) Seeler are discussed. The presence of infrequent clamp connections, dikaryotic hyphal cells and conidia, and the colour reaction with diazonium blue B all suggest thatH.blepharistomais a basidiomycete. However, failure to observe a basidial stage precludes assignment to known orders of basidiomycetes.

ISSN:0008-4026    

DOI:10.1139/b81-219

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

Cultures were grown under a constant stream of gas of known composition to eliminate accumulation of any volatiles produced by the fungus. CO2-free air completely inhibits colony initiation. Air containing 1% CO2allows colony initiation to the same extent as occurs in plugged, nonaerated controls, while "normal air" (ca. 0.03% CO2) causes initiation to be delayed to a variable extent.

ISSN:0008-4026    

DOI:10.1139/b81-220

出版商:NRC Research Press    

年代:1981

数据来源: NRC

摘要:

During the past century, forests in the vicinity of Sudbury, Ont., have been either destroyed or disturbed by logging, fires, and industrial pollution. These factors have produced an atypical mosaic of vegetation communities. This study investigates the patterns of plant communities that characterize this disturbed ecosystem.Nine major plant communities were found to predominate. These were determined by classification of the tree stratum with the aid of a hierarchical cluster analysis that was applied to data gathered from 142 quantitatively sampled field sites.These communities tend to be regulated by topography, soils, and distance from pollution sources. They can be grouped into two main types. The barren, birch transition and maple transition communities form a grouping that is attributed to pollution whereas the remaining six types are typical of the hemlock – white pine – northern hardwoods forest. The first three communities are restricted to the industrially disturbed region near Sudbury. Since they are peculiar, their dynamics are unknown and require further autecological research. Such an investigation could provide valuable insights into the pattern of succession in an ecosystem that is regulated by human activities.

ISSN:0008-4026    

DOI:10.1139/b81-221

出版商:NRC Research Press    

年代:1981

数据来源: NRC