This book is about bryophytes and lichens in the Arctic and Antarctic. It considers the evolution and adaptations of the polar floras, and the role of these plants in the vegetation and in the functioning of tundra ecosystems. The study of plant ecology in the polar regions has advanced dramatically in recent years as a result of work initiated in the Antarctic during the International Geophysical Year (1957–58), and in both Arctic and Antarctic as part of the International Biological Programme Tundra Biome investigations. Much attention has been focused on bryophytes and lichens because of their obvious abundance in local communities. The work has been broad in scope, ranging from phytogeography to physiological ecology, and from vegetation ecology to reproductive biology. The results, as synthesised here, are of relevance far beyond the polar regions, because they make a substantial contribution towards a general understanding of the environmental relationships of bryophytes and lichens. It should be noted, however, that mosses are of considerably greater ecological significance in the tundra than liverworts; they have consequently received more emphasis in research and therefore in the present text.

Authorities for most of the plant names cited in the text can be found in the following: mosses – D. M. Greene (1986), Steere (1978a); hepatics – Schuster (1966–80), Grolle (1972); lichens – Thomson (1984), Lindsay (1974); vascular plants – Greene & Walton (1975), Scoggan (1978–79). Where differences occur, the nomenclature used by the first-mentioned authority for each group has been followed.