摘要:

The forest history around Marion Lake in southwestern British Columbia is reconstructed using plant macrofossil analysis. A comparison with a previous reconstruction based on pollen and spore analysis reveals a good correspondence between pollen and macrofossil zones. Significant improvements in the reconstruction of forest history are possible by combining the study of pollen and macrofossils.Thuja plicatamacrofossils do not appear at Marion Lake until 6000 BP, contradicting previous suggestions of red cedar presence as early as 10 000 BP. Although not common at present,Taxus brevifoliamay have been an important component of the forest prior to the arrival ofThuja. Fluvial input of macrofossils is important at Marion Lake. Charcoal also appears to enter the lake primarily during periods of high runoff and erosion in the watershed, suggesting the need for caution in the interpretation of charcoal data from stream-fed lakes. Increases in total influx coincide with evidence for increased precipitation after 7000 BP. Marked reductions in macrofossil influx coincide with periods of peat deposition upstream from the present lake. Relative percentages of conifer needles are unaffected by changes in influx.

ISSN:0008-4026    

DOI:10.1139/b87-300

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Forty-five boulevard green ash (Fraxinus pennsylvanicavar.subintegerrima(Vahl) Fern.), both male and female trees, were selected and numerous morphometric measurements were obtained. Multivariate and univariate techniques applied to the data suggested three crown shape classes based on the pattern of crown diameter changes. The crown shape classes were identified as broad and rounded (group C) to tall and conical (group A), with an intermediate category (group B). Although tree age was not significantly different, group C trees tended to be larger with larger crown areas and basal main-stem diameters compared with groups A and B, which were not different. A visual rating analysis of the woody frame revealed that group A trees tended to have an excurrent form, whereas group C trees were predominately decurrent. When comparing sexes, it was found that male trees were larger, with larger crown areas than females, and they had a greater ratio of crown area to basal stem diameter. The crowns of male trees were generally branchier, with more foliage per unit crown volume than females. It appears that, in terms of growth and form, male trees are probably better suited for use as boulevard trees than female trees. Differences among groups and between sexes are discussed in relation to factors like apical control and reproductive sinks.

ISSN:0008-4026    

DOI:10.1139/b87-301

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The type species of two monotypic anamorph genera of Hyphomycetes are described and illustrated, and their conidiomatal anatomies are contrasted.Stromatographium stromaticum, the anamorph ofFluviostroma wrightii(Ascomycetes, Sphaeriales), has conidiomata referred to as amphistromatic synnemata, with pseudoparenchymatous stromata at both ends of the stipe.Stromatostilbellais considered a synonym ofStromatographiumv. Höhnel.Acrostroma annellosynnemagen. et sp. nov. (teleomorph unknown) produces conidiomata termed acrostromatic synnemata, because they have an apical pseudoparenchymatous stroma from which conidiophores arise.

ISSN:0008-4026    

DOI:10.1139/b87-302

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The benthic marine algal order Gigartinales (Rhodophyta) is introduced, and a key to the families found between Cross Sound, Alaska, and northern Washington is provided. The family Dumontiaceae is monographed. Ten of 16 currently recognized genera and 14 of some 48 recognized species are described and illustrated:Constantinea rosa-marina(Gmelin) Postels et Ruprecht,C.simplexSetchell,C.subuliferaSetchell,Cryptosiphonia woodii(J. G. Agardh) J. G. Agardh,Dilsea California(J. G. Agardh) Kuntze,Dumontia contorta(Gmelin) Ruprecht,D.simplexCotton,Farlowia mollis(Harvey et Bailey) Farlow et Setchell in Collins, Holden, et Setchell,Neodilsea borealis(Abbott) Lindstrom,N.natashaeLindstrom,Orculifilum denticulatumLindstrom,Pikea californicaHarvey,Thuretellopsis peggianaKylin, andWeeksia coccinea(Harvey) Lindstrom.Farlowia compressaJ. G. Agardh is recognized as a taxonomic synonym ofF.mollis, andPikea robustaAbbott as a taxonomic synonym ofPikea californica. Vegetative keys to the genera and species of the family are also included. Basionyms, synonyms, type specimens, type localities, and what is known about life histories, distributions, phenologies, and habitats of the species are given. Representative specimens are cited.

ISSN:0008-4026    

DOI:10.1139/b87-303

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Female gametogenesis and fertilization ofSphagnum palustrewere compared with data on different species ofMnium(Bryatae) and onFossombronia angulosa(Marchantiatae). The general organization of the archegonium is identical with that observed in other bryophytes. The progamete appears as an odd-shaped 23 μm long cell. Numerous organelles are responsible for the relatively high electronic density. The progamete divides into two cells, the larger being the egg. Different stages of the maturation process of the female gamete are described. The one major difference found is in the origin of the mucopolysaccharides surrounding the female gamete in the archegonium. A stage corresponding to the contact of the two nuclei just prior to fusion was observed in the fertilization process.

ISSN:0008-4026    

DOI:10.1139/b87-304

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Plants from six New Jersey populations ofDichanthelium clandestinum, a perennial grass with chasmogamous and cleistogamous flowers on the same individual, showed significant differences in their responses to decreasing light and soil moisture, but chasmogamous reproductive effort was always less than cleistogamous. In an experiment with three light treatments, populations were significantly different in biomass allocation to chasmogamous and cleistogamous reproduction and varied as to which light treatment produced the most significant difference between chasmogamous and cleistogamous allocation. In an experiment using soil moisture gradient boxes, chasmogamous reproductive effort remained relatively constant over the moisture gradient for all six populations; however, for five populations, percentage biomass allocation to cleistogamous reproduction was significantly lower at low soil moistures. The population responses formed a continuum from no difference in allocation to cleistogamy along the moisture gradient to a sharp drop in cleistogamous allocation at the lower end of the gradient to a relatively steady decrease in cleistogamous allocation with decreasing soil moisture. These results indicate genetically based differences in phenotypic plasticity and underscore the need to use more than one population of a species when research is conducted on variation in relative allocation to chasmogamous and cleistogamous reproduction along environmental gradients.

ISSN:0008-4026    

DOI:10.1139/b87-305

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Trillium nivaleRiddell is an early-blooming spring ephemeral, which occurs in widely scattered, small populations throughout the eastern United States. Nine populations from previously glaciated regions of Ohio were surveyed by enzyme electrophoresis to determine the extent of the genetic variation present in the species. Twelve enzymes, coded by 25 putative genetic loci, were assayed during the study. Within populations, either very low amounts of genetic variation or total genetic uniformity were detected. The low levels of genetic variation are perhaps correlated with the reproductive biology ofT.nivale.

ISSN:0008-4026    

DOI:10.1139/b87-306

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The sequence of events and morphology of structures were similar during early floral development ofAgalinis tenuifoliaandA.fasciculata. The lateral-posterior calyx primordia were initiated first, followed by the middle-posterior primordium, and lastly by the two anterior primordia. The corolla primordia arose in an anterior to posterior succession, then the four stamen primordia were initiated simultaneously. Later the gynoecium originated as an oval-shaped ridge. Two depressions within it became locules, and the two sides of the cleaved ridge separating them met and formed a septum. A placenta formed in each locule and numerous ovules were initiated on it. Zygomorphy was apparent in the calyx, corolla, and androecium during the primordial stage. Organogenesis in the calyx was rapid so that the calyx lobes and tube were well formed before organogenesis of other floral parts. Except for those of the calyx, floral character states distinctive for each species were manifested late in development of the floral bud.

ISSN:0008-4026    

DOI:10.1139/b87-307

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

The biology ofDicyma pulvinata(Berk. & Curt.) v. Arx, a mycoparasite ofCercosporidium personatum(Berk. & Curt.) Deighton, was investigated under both laboratory and field conditions. At 26 °C, conidia ofD.pulvinataclose to both hyphae and conidia ofC.personatumgerminated within 11–17 h. Visible signs of colonization of lesions ofC.personatumbyD.pulvinataappeared within 58–65 h (21–31.5 h leaf wetness).Dicyma pulvinatawas an effective protectant when plants were exposed to continuous leaf wetness at 26 °C for 5 days. In field microplot studies, lesions ofC.personatumwere visibly colonized by both mutant and wild-type isolates ofD.pulvinatawithin 4 days after applying their conidial suspensions. Environmental conditions during this 4-day period were 40 h leaf wetness, 60 h of 23–28 °C (optimal temperatures for growth of the wild-type isolate), and 17.31 cm rainfall.

ISSN:0008-4026    

DOI:10.1139/b87-308

出版商:NRC Research Press    

年代:1987

数据来源: NRC

摘要:

Secondary succession ofSphagnummosses was studied for 7 years along a belt transect in a bog that had been impacted by sodium chloride highway deicing salts. Laboratory studies onSphagnum fimbriatumWils., the dominant recolonizing species, were conducted to determine its salt tolerance level and ability to reproduce from spores and fragments across a salt gradient. Vegetative reproduction was also compared with that of four other recolonizing species.Sphagnum fimbriatumrepresented a high percentage of all recolonizingSphagnumand generally began growing on low hummocks in quadrats where the salt content of the interstitial peat pore waters had dropped to about 300 mg/L as chloride. This salt concentration was also found to be the basic tolerance limit for mature plants and reproducing spores and fragments. The success ofSphagnum fimbriatumas a pioneer species seems to be associated with its prolific production and probable dispersal of spores, its superior vegetative reproduction, its tolerance of mineralized waters, and its ability to grow on hummocks out of direct contact with mineralized waters.

ISSN:0008-4026    

DOI:10.1139/b87-309

出版商:NRC Research Press    

年代:1987

数据来源: NRC