Calluna Salisb.

Abstract

A biological and ecological account of Calluna vulgaris, beginning with a taxonomic description and summary of geographical and altitudinal distribution (with maps), followed by a discussion of habitat range with special reference to climate and soil (mechanical and chemical analyses of 3 examples of profiles beneath dominant Calluna) and to the reaction of the plant upon its habitat. For the first time a provisional grouping of British plant communities containing Calluna (along phytosociological lines) is given: 21 types are recognized and described, with complete lists of species (including bryophytes and lichens) from representative examples of each. The responses to biotic factors (fire; grazing by sheep, cattle, grouse, rabbits) are considered, and variations in shoot growth-form and rooting depth discussed in relation to environmental conditions. The literature on mycorrhiza in Calluna is briefly reviewed; and an outline given of the sequence of phases in the normal life-history ("pioneer, building, mature and degenerate"). Lists are included of insect visitors to the flowers and of insects feeding on the plant; also data on the influence of temperature and water supply on seed germination. Seedlings are described and illustrated; brief reference is made to fungal diseases and to the history of the species as a member of the British flora. 144 references are listed.