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Of the world's major biomes, tundras, including Antarctica and Green land, occupy about 15% of the land surface. These treeless areas, above treeline (alpine ) or beyond treeline latitudinally (arctic ) , contain relatively few plant species. The plants that are preadapted to tundras have bcen se lected by environmental regimes that contain less biologically usable energy than in other biomes. Yet Hare (78 ) has shown that even in the Canadian Archipelago the Arctic is not a heat sink on a yearly basis, for solar radia tion amounts to 35-40 kilolangleys/year (0-5 kly /year in net radiation), compared with 1 5-20 kly/year at treeline in Alaska and Keewatin. While altitudinal and latitudinal treeline conforms quite well to the lOoC mean for the warmest month, Bryson (46 ) reports that the northern limit of trees also corresponds with the southern limit of the arctic frontal zone in sum mer. This dynamic boundary may be controlled by vegetational differences in albedo and surface roughness. The functioning of plants, as influenced directly and indirectly by tem perature, becomes central in determining the various strategies that have evolved to enable them to cope with these heat-deficient ecosystems. The purpose of this review is to bring together recent information and theories on the adaptive mechanisms which enable plants to survive and function in environments with cool, short summers and cold, long winters-save for tropical alpine environments where winter comes nearly every night and, where possible, to relate these findings to the pattern of species and communities in different tundras. Much research has been done in recent years on the floristics, plant com munities, soils, ecophysiology, and now the ecosystems of different tundras. A few key books and articles that speak to this background of information are those of Schroeter ( 169 ) , S0rensen (176 ) , Polunin ( 1 50, 152 ) , Bliss
L. C. Bliss (Mon,) studied this question.