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(1) In Calluna-dominated heathlands managed by periodic burning, vegetation composition is influenced by the ability of species to regenerate rapidly after a fire. Experiments were carried out, using a number of heathland species, (i) to investigate the effects on germination of exposing seeds to short periods of heat treatment and (ii) to determine the influence of fire temperature on vegetative regeneration. (2) In two species, Genista anglica and Hypericum pulchrum, evidence was obtained of stimulation of germination following short periods (30 s-2 min) of pre-treatment at 100 IC. There was some indication that in Vaccinium vitis-idaea a vernalization requirement might be overridden by a very short period of heating at 100 IC. Apart from these instances, there was little evidence of 'fire-adaptation' of this kind. Treatments at 200 0 C, or for more than 2 min at 100 0C, either killed seeds or reduced germination in most of the species tested. (3) All tested species (except Juniperus communis) regenerated vegetatively after burning at 600 0C, but in most cases a temperature of 800 0C resulted in less recovery. (4) These findings emphasize the importance of controlling management fires so that canopy temperatures are held within the range 400-600 0C and ground-surface temperatures rise little above 100 OC. These conditions should be sustained for no more than 2 min as the fire passes through the vegetation.

Calluna-dominated heathlands are widespread in N. Britain, especially in the eastern and central part of Scotland. The plant communities of these heathland ecosystems are influenced by regular burning as a land management practice. In a well-controlled fire, regeneration takes place both vegetatively (from surviving stem bases or underground rhizomes) and from seed. But there is always a post-fire succession taking place even in this brief period of vegetation recovery. In order to understand the biological mechanisms operating in the post-fire succession, the present work was carried out to examine regeneration behaviour of different species. Three 'regenerative strategies' were identified: I. Woody low-shrubs with slow bud development to begin with, followed by vigorous and profuse branching, becoming dominant after two years; II. Small herbaceous hemicryptophytes; sprouting not as prolific as in plants of group I, but more vigorous than in plants of group III; III. Geophytes with rapid development, important in the first 2-3 years.

Summary Calluna vulgaris, in certain habitats, provides useful grazing for herbivores; management is generally by burning, with the aim of promoting vigorous production of young shoots by vegetative regeneration for the stem base. However, the capacity for such vegetative regeneration declines with age. The general morphology of the plant is described, with particular reference to the sequence of development in a single season's growth and to the stages in resumption of growth after overwintering. On this basis, an interpretation is given of the responses to grazing and burning, with evidence derived from detailed observation of treated plants and from transverse sections of stems. Light grazing at the periphery of the plant causes (i) the growth of a few of the uppermost short shoots into new long shoots, and (ii) the appearance of clusters of shoots from lower, woody, parts of the branches. Heavier or more sustained grazing emphasizes the second of these responses. Vegetative regeneration after burning is also of the second category, confined to undamaged positions near the base of the stem. The clusters of shoots appear at the points of origin of existing or former branches. The conclusion, derived both from morphological observations and from evidence of the deep‐seated origin of these new shoots, is that they are derived from persisting dormant buds on the close‐packed nodes just below the base of each long shoot. These nodes belonged to the overwintering end‐of‐season short shoot from which the long shoot developed.