摘要:

The Lower Miocene fossiliferous bed of Canenx (Landes), accurately dated from its marine fauna, has yielded large quantities ofPinuspollen. Despite careful biometric observations, specific determination of these pollen grains is difficult, unless the ectexine structure of the air-sacks is taken into account. Light and scanning electron microscopy of the ectexine of the air-sacks of about 100, out of roughly 150 present-dayPinus-species, mainly American, has shown that the ectexine structure is always alveolate. The various features and parameters were found to be generally constant at species level. Using this new criterion, about 20 different forms could be distinguished among the fossilPinuspollen from the Canenx bed, 10 of which were identifiable to species level. Pollen of Asiatic, especially Chinese,Pinusspecies was poorly represented in our herbarium material, making the study of these floras difficult; however, the presence at Canenx of a few Asiatic genera is indicated, e.g.Cathaya,which nowadays grows in China. The study has provided fresh evidence for the existence of a large floristic province, the “Mixed mesophytic forest” of Graham (1972) in the Northern Hemisphere during the Middle Tertiary (Upper Oligocene and Miocene).

ISSN:0017-3134    

DOI:10.1080/00173137309428838

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

14C-dated finds of seeds ofAlnus incana(L.) Moench. andA. glutinosa(L.) Gaertn. are described and considered in relation to the pollen curves of selected tree spp.A. incanaimmigrated first and spread widely in the area, though with local retardation explainable hydrologically, between ca. 6000–5000 B.C.A glutinosa,with its greater thermic requirements, reached the area much later. Its presence on the Frosta peninsula is documented from ca. 1600–700 B.C. whereafterA. incanabecomes the dominant, or sole, alder species once again.

ISSN:0017-3134    

DOI:10.1080/00173137309428839

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

Some Companulaceae pollen have been studied by means of scanning and transmission electron microscopy and two clearly different pollen types are described.

ISSN:0017-3134    

DOI:10.1080/00173137309428840

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

The acetolysed exine ofBarringtonia calyptrocalyxpollen was investigated by means of light, transmission electron, and scanning electron microscopy of whole and sectioned grains. A simple method of sectioning using a freezing microtome is described. The exine is shown to consist of an endexines. str.which does not stain with basic fuchsin and is more electron-transparent, and an ectexine which stains and is more electron-dense. A fully integrated description is attempted which is shown to be convertible to a numerical code system for computer processing. The structural modifications of the exine are analysed in relation to harmomegathic functioning and it is suggested that they may represent protective closing devices of the apertural area and stress absorbing structures. The evolutionary origin of these structures is discussed briefly andB. calyptrocalyxpollen is shown to be the highly specialized end product of a series which starts with a simple trieolpate pollen type.

ISSN:0017-3134    

DOI:10.1080/00173137309428841

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

A short review of basic definitions relating to the term “tectum” is given. Pollen grains with a tectum perforatum are described and defined. A new term “microreticulate”, is proposed for describing exine structures which consist of minute reticula with thin muri (< 1 μ in breadth) encompassing small lumina (< 1 μ in diameter). The term “reticulate” is to be restricted to reticulate exinessensu stricto.i.e., provided with distinct muri, frequently about 1 μ or more in breadth, and with lumina larger than 1 μ in diameter.

ISSN:0017-3134    

DOI:10.1080/00173137309428842

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

Pollen ofTupidanthus calyptratusand four species ofPlerandrawere examined by light microscopy using both bright field and interference contrast illumination. Pollen ofPlerandra pickeringiiwas also examined by scanning electron microscopy. The elongate grains ofTupidanthuswith short and narrow ora are distinct from the spheroidal or suboblate grains ofPlerandra.The palynological characters together with other data suggest thatTupidanthusshould occupy a higher systematic position thanPlerandra.The pollen ofPlerandraappears to be a generalized type among the primitive Araliaceae but is characterized by the large, laterally extended ora. Interspecific variations also occur among thePlerandraspecies studied. The pollen of bothTupidanthusandPlerandrais distinguishable from that ofTetraplasandraand close relatives by the absence of inner nexinous breaks and the non-thickened exine of the polar region.

ISSN:0017-3134    

DOI:10.1080/00173137309428843

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor

摘要:

Pollen grains of 5 specimens of the heterostylousW. viscosissimawere studied by light- and scanning electron microscopy. A striking pollen dimorphism correlated with a marked dimorphism of the reproductive floral organs was observed. Besides common size and shape differences the pollen grains of long- and brevistylous forms differ markedly in the number of apertures, in the relative length of the ectoapertures and in the nexine thickenings, as well as showing differences in the supratectal sexine elements and in the fine details of the tectum. The taxonomic significance of these differences in pollen characters is discussed.

ISSN:0017-3134    

DOI:10.1080/00173137309428844

出版商:Taylor & Francis Group    

年代:1973

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:10.1080/00173137309428837

出版商:Taylor & Francis Group    

年代:1973

数据来源: Taylor