摘要:

The TEM observations of the perispore reveal: (1) The presence of the perispore in many families which were earlier considered non-perinate. However, this perispore differs in nature from the LM-detected layer. (2) The conventional perispore is double layered with septa running in between the two, and may be acetolysis-resistant, acetolysis-affected or acetolysis-soluble. (3) The so-called loose perispore in Aspleniaceae and Aspidiaceae is the only LM-visible layer which gives the false impression of being loose. (4) It is fibrillar in nature, although it differs in certain genera. Although extra exosporial in nature, it is doubtful whether the equatorial collar inPteris-group of ferns, the elaters inEquisetumand the proximal cup-like structures of the spore coat in Gleicheniaceae, have a distinct position in the line of evolution of perispore. Also, it is not yet definite whether the genetic control regarding the patterning of the perispore is passed through the apertural “fissures” in the developing exine.

ISSN:0017-3134    

DOI:10.1080/00173138009424999

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

In the pollinium ofZeuxine strateumatica(L.) Schlecht., the massulae are held together by viscin threads. These threads are elastic in nature and seem to lack lignin and sporopollenin.

ISSN:0017-3134    

DOI:10.1080/00173138009425000

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Pollen ofAustrobaileya scandensWhite, fixed in FAA, has been investigated by LM, SEM and TEM techniques. The combination of characters is remarkable among the pollen of extant angiosperms: the grains are globose, anasulcate, tectate-perforate, rugulose (reticulate), columellate; the sulcus margin is very marked; the endexine is considerably laminated at the aperture border and slightly laminated outside the aperture. These features underline the isolated systematic position of the Austrobaileyaceae between the Magnoliales and Laurales. Furthermore, the pollen ofAustrobaileyaresemblesClavatipollenites, one of the oldest (probable) angiosperm fossils. It may therefore be interpreted as especially archaic among the angiosperms.

ISSN:0017-3134    

DOI:10.1080/00173138009425001

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

In the genusLinumsect. Linastrum, pollen grains interpreted as primitive are characteristic of most Old World species and species of southeastern South America and Mexico. The Old World species are more uniform but the few species of the Mediterranean region and the single species of India possess larger grains, thicker exine or more polymorphic sculpturing. In South America, pollen grains of the species of Peru and Chile are the largest, have the thickest exine and the most polymorphic exine sculpturing of any on the continent. The greatest variation is shown by the North American species. Within theLinum rigidum-complex are found the largest pollen grains of the genus with the thickest exine and the greatest number of apertures. These species are considered the most specialized in the genus with respect to their pollen morphology.

ISSN:0017-3134    

DOI:10.1080/00173138009425002

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

In some specimens ofLophophytum mirabilehexacolporate tetrahedral pollen grains occur along with the normal tricolporate ones. It is shown that there are two kinds of tetrahedrons, mirror images of each other, occurring with approximately 50% of each kind in one preparation (i.e. one anther). It is suggested that the tetrahedrons are formed in tetrads.

ISSN:0017-3134    

DOI:10.1080/00173138009425003

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A technique for observing anthers fixed and embedded for a transmission electron microscope (TEM), after resin removal, with a scanning electron microscope (SEM), is described. This technique affords two different types of images from the same pollen grain, bidimensional by TEM and tridimensional by SEM.

ISSN:0017-3134    

DOI:10.1080/00173138009425004

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The genusAriadnaesporites(Potonié) Tschudy is recorded for the first time from the Cretaceous, probably Upper Cretaceous, of Nigeria. It is represented byA. nigeriensisn.sp. and two additional megaspore types together with six different types of associated microspores. The order Salviniales is further represented by megaspores and microspore massulae belonging to the genusAzollaLam.

ISSN:0017-3134    

DOI:10.1080/00173138009425005

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Assemblages of Recent and sub-Recent dinoflagellate cysts are described from the southern Beaufort Sea, offshore Mackenzie Delta region, Canadian Arctic, and include the new taxaSpiniferites frigidusHarland & Reid,Multispinula minutaHarland & Reid, andRottnestia amphicavataDobell & Norris. These assemblages, which appear to be unique to Arctic waters, are dominated byOperculodinium centrocarpum, and compared to assemblages found in north-temperate seas, also dominated byOperculodinium centrocarpum, are ten times less diverse. The three new species described herein may prove to be indicators of the Arctic environment. Several genera of Recent cysts that were not originally supplied with Latin diagnoses are validated.

ISSN:0017-3134    

DOI:10.1080/00173138009425006

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Measurements of atmospheric pollen concentration were made at different sites of the Po Valley, Italy, during the winter of 1978. The concentration was determined with volumetric samplers both near the ground and at different heights up to 500 m. OnlyCorylusandAlnuspollen grains were found during the experimental period. Due to the large quantity of grains released and the detailed information available about the source areas, theCoryluspollen was used to investigate the features of atmospheric transport. It was found that the three-dimensional patterns of pollen concentration are strongly influenced by meteorological conditions. Moreover, it appears that pollen is present in the atmosphere for a longer time with respect to the emission period, due to the relevant effect of the resuspension of the deposited pollen grains. This effect is detectable at all the sampling points, and not only near the sources.

ISSN:0017-3134    

DOI:10.1080/00173138009425007

出版商:Taylor & Francis Group    

年代:1980

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:10.1080/00173138009424998

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor