摘要:

SEM observations of 12 species of the generaTriticum, Hordeum, Avena, Secale, Panicum, Setaria, BromusandGlyceriacontribute to a better understanding of the exine sculpture and lead to the description of 4 types. No fundamentally new features were revealed and the scope of SEM may be limited to that context. A higher degree of reliability in the identification of the pollen types may be achieved if all available LM and SEM characters are combined and if the ecological differences of those wild grass species ranging within the pollen size of cereals are taken into consideration as an exclusive factor. Finally the existence of a taxonomic patterning of the exine sculpture is confirmed.

ISSN:0017-3134    

DOI:10.1080/00173137909424973

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The pollen grains and spores constitute an important morphological entity, reflecting the facts and facets of plant evolution. Among the various characters of the exine, the aperture is considered to be the most conservative. The grains are primorphous (apertures indistinct) in Thallophyta, trimorphous (trilete, monolete and alete) in Archegoniatae and polymorphous (colpate, colporate, porate, etc., the apertures varying in number and form), in the angiosperms. The trimorphous condition is characteristic of the preangiospermous Archegoniatae, and its occurrence in the angiosperms may be considered to provide an indication of the primitive taxa of the group. Against this background, it is argued that the angiosperms are triphyletic, having three independent phylogenetic stocks, namely the Monocot stock, the Magnolian dicot stock, and the Ranalean dicot stock, in that order of phylogenetic succession

ISSN:0017-3134    

DOI:10.1080/00173137909424974

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The stages of the sporoderm morphogenesis ofPsilotum triquetrumare studied by TEM from the newly formed tetraspore stage to the release of the spores. First the tetraspores are overlaid with the “foliated substructure of the exospore”, which consists of some long, thin, anastomosed sheets, and shows a protruding narrow fold at the region of the future aperture; thereafter, sporopollenin without a definite structure gradually accumulates on the substructure thus forming the middle and outer parts of the exospore. Finally, a thin perispore develops close to the surface of the exospore. Either simultaneously or with variable delay, a “pseudo-endospore” fairly thick at the apertural region but very thin elsewhere, appears between the exospore and the spore cell. The endospore itself has not developed when the spore release occurs. This ontogenetical process ofPsilotumis very similar to that of Filices, whereas it obviously differs from that of other Pteridophytes

ISSN:0017-3134    

DOI:10.1080/00173137909424975

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The environment during the Mid-Tertiary comprised of tropical rain forest under oceanic climate and moderately hilly topography with about 2000 mm precipitation. Gradual increase in tropical deciduous elements, events of diastrophism, continentality of climate and immigration of conifers characterised Mid-Miocene to Pliocene. Cool and moist subtropical and temperate forest with precipitation from 1000–1500 mm were established in the western Himalaya during the early Pleistocene. Moist climate had continued during the Weichselian in the Kathmandu Valley, Nepal, but for the progressive aridity in the Kashmir valley, Rajasthan, Gujarat and Maharashtra since the Weichselian times. The evolution in the early hominids, the emergence ofHomo sapiensand the progressive evolution of the Palaeolithic, Mesolithic and Neolithic cultures were not governed by drastic changes in climate. The commencement of food production was circumstantial rather than induced by change in climate

ISSN:0017-3134    

DOI:10.1080/00173137909424976

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Three new pollen forms related to tropical taxa have been recorded from the Hungarian Neogene.Manikinipollis tetradoidesKrutzsch was previously known only from the Miocene of Byelorussia. It seems to be related to the tropical family Periplocaceae.Goerboepollenites erdtmaniigen. et spec. nov. resembles some genera of the Upper Cretaceous tropical stemma Normapolles. Pollen grains comparable to extant tropical members of the family Moraceae were recognized by means of scanning electron microscopy

ISSN:0017-3134    

DOI:10.1080/00173137909424977

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Pollen grains of eight different species from the generaComarum, Fragaria, PotentillaandSibbaldia, usually considered as one type, the “Potentillatype”, were examined and morphological features making distinction possible are described

ISSN:0017-3134    

DOI:10.1080/00173137909424978

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

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

ISSN:0017-3134    

DOI:10.1080/00173137909424972

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor