摘要:

Three different types of decay have been observed in exines of Normapolles type from anther 143 A 3, found in a clayey sand in the Upper Cretaceous fluviolacustrine sediments at Åsen. The outer exine layer (tectum) is penetrated by numerous radial needlepores, interpreted as widened microchannels. The tectum and, in some cases, also the infratectal layer and the foot layer (solum) may be penetrated by irregular, tunnels (>500 nm in diameter), sometimes branching into finer tunnels (50–100 nm) at the transition to the infratectal layer. Still finer holes (15–40 nm) have been observed in all exine layers. They occur as a rule in zones, separated by about 200 nanometer from the surfaces of the exine layers, needle-pores and tunnels. No indisputable evidence of the agents responsible for these types of decay has as yet been recognized.

ISSN:0017-3134    

DOI:10.1080/00173139309428982

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Archaeological-palaeogeographical studies on the Russian Plain make it possible to trace the history of man-induced changes of the landscapes from the Mesolithic to the present time. Palynological data suggest that the economic strategies of the primitive society inhabiting the area were strongly influenced by climatic fluctuations and the related changes in vegetation and animal population of the different zones.

ISSN:0017-3134    

DOI:10.1080/00173139309428983

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Birch pollen concentrations recorded by volumetric sampling for a three year period on the rural Baltic island, Gotland, are presented and compared with the birch pollen records for the same period in Stockholm. Since the incidence of birch pollen allergy among the farmers on the island was found to be lower than on the mainland it was generally believed that the airborne birch pollen concentration on Gotland was relatively low. Although birch is only scattered on the island, theBetulapollen concentrations in the years investigated appear to be as high as or higher than those in Stockholm, where birch is one of the main elements of the urban vegetation. The reasons for the abundance of birch pollen in the air of Gotland in relation to the low figure of sensitisation to birch pollen are discussed.

ISSN:0017-3134    

DOI:10.1080/00173139309428984

出版商:Taylor & Francis Group    

年代:1993

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:10.1080/00173139309428971

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor