ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1973.tb01728.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Some of the principal advances in our knowledge of lichens made since the time of E. M. Holmes are briefly reviewed. Floristic studies on British lichens have continued and distribution maps of particular species are now being produced. These studies have shown that many species have disappeared from areas affected by air pollution by sulphur dioxide. Lichen taxonomy has seen the acceptance of chemical characters as valid taxonomic criteria, and the realization that ascus types, ascocarp structure and ascocarp ontogeny are more important at the generic level than ascospore characters alone. Lichens are not now thought of as a single taxonomic group but as fungi related to various orders of non‐lichenized Ascomycotina, united only in their common method of nutrition (symbiosis with algae); some lichenized and non‐lichenized species with identical types of ascocarps are consequently being treated as members of the same genus. Considerable progress has been made in describing lichen communities characteristic of particular substrates and situations and in understanding the factors which may affect the occurrence of particular species. Lichens have proved to be particularly valuable indicators of mean air pollution levels and scales for the estimation of these levels based solely on the lichen vegetation have been devised. Physiological and ultrastructural studies on lichens have progressed rapidly in the last decade. Carbohydrates have been demonstrated to move from the algal to the fungal component and the mobile carbohydrates found to differ in lichens with different genera of algae. The algal and fungal partners have been isolated and studied in pure culture. Most attempts to synthesize lichens have met with little success but in 1970 a thallus was formed from its components in culture. It is now possible to grow some lichens under controlled conditions in the laboratory and these techniques, together with transplant experiments, will clearly assume considerable importance in the investigation of taxonomic and ecological problems in the future. Little progress has been made in the study of lichen cytology or the factors affecting the establishment of lichen thalli. Lichens constitute an important part of some ecosystems and their decline due to anthropogenic influences is consequently a matter of concern for all biologi

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1973.tb01729.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

Because species concepts change and world distributions come to be better known, our picture of bryophyte distribution is subject to continual revision. Herzog's masterly phytogeographical analysis is cited as representative of the situation midway between Holmes's time and the present day. The modern position is reviewed, both for the British Isles and on a world‐wide scale. The link between taxonomic revisions and distributional studies is explored. The many recent contributions to our knowledge of bryophyte distribution are classified under several distinct heads. Attention is focussed on selected genera of outstanding interest. Finally, brief consideration is given to the wider implications of the various types of distribution stud

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1973.tb01730.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

摘要:

E. M. Holmes's major interests in the marine benthic algae were, like those of most of his contemporaries, taxonomic and floristic; he was much occupied with the acquisition, for areas of the British Isles, of new records of species known already elsewhere. Records established by Holmes and his contemporaries have increasingly been subjected to examination by means of more recent laboratory and field techniques. Data thus gathered continue to reveal connections between taxa hitherto considered distinct; it is mainly this revealed capacity for structural and reproductive variation, at many levels, in the benthic marine algae that has led to amendment by posterity of earlier taxonomic opinions. Even in the areas widi a long tradition of benthic marine phycological study, there remains much to be understood; apart from the need for more workers and for yet more sophisticated research techniques, the biotic situation is itself dynamic. Nevertheless, the importance of the ground work achieved and herbaria assembled by Holmes and his contemporaries (especially Batters) cannot be denied.

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1973.tb01731.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY

ISSN:0024-4074    

DOI:10.1111/j.1095-8339.1973.tb01728a.x

出版商:Blackwell Publishing Ltd    

年代:1973

数据来源: WILEY