摘要:

Chromosome numbers for four species ofCladophorafrom coastal North Carolina are presented. The basic chromosome number is six, with three median and three submedian chromosomes.Cladophoraspecies represent a polyploid series, with numbers of 12, 18, 24, 30, and 36 found in the present study. Three chromosome size classes (large, medium, and small) are represented by individual species. Correlations between each species' karyotype and its morphology and distribution are discussed. Karyotype morphology and probable evolutionary trends in the form sections Glomeratae and Rupestres are presented. Mechanisms responsible for reduction in chromosome size in both form sections are discussed in relation to similar reduction patterns in flowering plants with significant heterochromatin content.

ISSN:0017-0070    

DOI:10.1080/11263508709431642

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Embryology ofHelichrysum rupestrevar.messeriiPignatti has been studied. The anther is tetrasporangiate and its wall development conforms to the Dicotyledonous type. The tapetum corresponds to the Periplasmodial type and its uniseriate cells show a dual origin. Microsporocytes are linearly arranged; tetrahedral, isobilateral or decussate pollen tetrads were observed. The ovule is anatropous, unitegmic, tenuinucellate and endotheliate; the peripheral nucellar cells begin to degenerate after the tetrad stage, when the endothelium is already differentiated. This integumentary layer surrounds the mature embryo sac almost completely remaing uniseriate with uninucleate cells after fertilization. The unicellular ovular archeosporium functions as the megaspore mother cell. The chalazal megaspore of the linear tetrad develops into a Polygonum-type embryo sac. The synergids are hooked at their micropylar region and show a filiform apparatus before fertilization. At this stage the primary antipodal cells increase in number. Unusual nuclear arrangement as well as precocious cell wall development has been observed in a few young gametophytes; in a single ovule a coenocytic megagametophyte has been observed with supernumerary nuclei and anomalous vacuolation. Fertilization is porogamous. Endosperm development is of Nuclear type. The embryogeny conforms to the Asterad type.

ISSN:0017-0070    

DOI:10.1080/11263508709431643

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

New taxa in the genus Stipa L. (Gramineae) from Puna flora of Argentina. - Two new Gramineae from Argentine flora are described,Stipa nicoraesp. nov. andStipa speciosaTrin. et Rupr. var.ciliatavar. nov. An analytical key of all the forms and varieties ofStipa speciosais also included. Both the new taxa can be considered characteristic elements of the Cuyano (southern Puna district).

ISSN:0017-0070    

DOI:10.1080/11263508709431644

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

On the typification of Allium lehmannii Lojac. (Alliaceae), a good species for Sicily and Calabria. - The comparison of the type-specimen ofAllium pallensL. subsp.sicilienseStearn., Ann. Mus. Goulandris,4: 161 (1978) preserved at Vienna (WU) and of the type-specimen ofAllium lehmanniiLojac., Fl. Sic.,3: 114 (1909) found at Palermo (PAL) and here designated, allows us to regard the two taxa as related to the same entity. In the authors' opinionAllium lehmanniiLojac. is to be considered as a good species. Its distribution for Sicily (living and dried specimens) and for Calabria (a single dried specimen from Sila) is outlined. A description, chromosome number (2n= 16) and some other general informations are also pointed out.

ISSN:0017-0070    

DOI:10.1080/11263508709431645

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Surface features of mature sporoderm inFossombronia caespitiformis, F. wondraczeckii, F. angulosaandF. echinata(Metzgeriales, Codoniaceae) were examined by scanning electron microscopy (SEM). Sporoderm layering of fresh-fixed and acetolyzed spores was studied by trasmission electron microscopy (TEM). Surface ornamentations of spores consist of spine-like and/or ridge-like markings which form species-specific patterns on the distal faces. Sporoderms have similar cross-sectional configurations, which include a fibrillar intine, removable by acetolysis, and two morphologically distinct exine layers, resistant to acetolysis. The inner exine consists of lamellae, parallel to the spore surface, composed of thin, long, parallel, closely spaced laminar units. The outer exine, which produces the spore surface ornamentations, is formed of thick, shorter, parallel, tightly appressed laminar units, impregnated with very dense material and variably oriented with respect to the inner exine lamellae. The internal sporoderms also subject to species variability. Internal sporoderm structure inFossombroniais quite unlike that of typical Metzgeriales or Jungermanniales and approaches the configurational complexity of the Sphaerocarpales and Marchantiales.

ISSN:0017-0070    

DOI:10.1080/11263508709431646

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

During the years from 1979 to 1984, macroalgal samples were taken every month in 15 stations, representative of the Venice littoral, in order to determine the species and the vertical distribution of phytobenthic associations. A great difference has been found with the results of previous papers (Schiffner& Vatova, 1938; Pignatti, 1962), due to the eutrophication increase. Many oligotrophic species, such as those belonging to the «Cystoseiraassociation» have disappeared, whereas some genera, once very abundant, are presently strongly reduced, for instanceLaurencia, PolysiphoniaandDasya. On the contrary many Ulvaceae have colonized all the studied area thanks to their adaptation to pollution. The percentage of Chlorophyceae has increased considerably, ranging from 20 to 34%, whereas Rhodophyceae decreased from 65 to 51%. Phaeophyceae percentage remained pratically unchanged ranging from 13 to 15%.Zostera marina, Zostera noltiiandCymodocea nodosa, once spread in all the lagoon, now only grow far from the urban wastes of Venice and the industrial effluents of Porto Marghera.

ISSN:0017-0070    

DOI:10.1080/11263508709431647

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Ecology of wetlands: grass-lands and freshwater marches. - The influence of the direct and indirect factors of the sites on the floristic composition of the wet and moist meadow communities of Czechoslovakia are discussed as well as their inclusion into the phytogeographical regions of the territory. Many examples showing the indicative value of the associations and subassociations sensu Braun-Blanquet are given in connection to the water regime and chemical properties of the soil.

ISSN:0017-0070    

DOI:10.1080/11263508709431648

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Oligotrophic wetlands in eutrophicated landscape. Augmentation of the antropogenic output of nutrients (N, P). - Our industrial and agricultural activities provoke a general eutrophication of our wetlands, lakes and swamps, not only due to the changing chemistry of our precipitations but also by seepage from cultivated areas and by inundations with nutrient-rich water from lakes, ditches and other waterbodies. This new state of the environment initiates a series of changes in most wet sites, e.g. reed-death, pseudoreedbelts on fens, «macrophorbisation» of oligotrophic straw meadows (Molinion, Eriophorion latifolii, etc.). Also protected areas undergo such changes. Nutrient gradients are assessed along transects from eutrophic to oligotrophic sites to be alble to detect nutrient fluxes and consequently buffer endangered sites (e.g. quaking mats).

ISSN:0017-0070    

DOI:10.1080/11263508709431649

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue

ISSN:0017-0070    

DOI:10.1080/11263508709431641

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor