96 BOTANICAL GAZETTE [july 



Subantarctic vegetation. — Of the several antarctic regions whose vegetation 

 has been recently studied, South Georgia seems of particular interest, both 

 because of its isolation and on account of the character of its vegetation, being 

 transitional between the truly antarctic type and the well developed sub- 

 antarctic associations found in such regions as the Falkland Islands. As a 

 result of visits to the island in 1902 and in 1909, Skottsberg 21 gives an inter- 

 esting account of the plant associations. The island is mountainous, some 

 peaks reaching 2000 m., and is largely covered with ice in the form of glaciers 

 moving down the valleys and reaching the sea in fiords. There is little seasonal 

 difference in climate, the summer mean temperature being about 4 C, and the 

 winter about — 1° C. Exposure is a factor of prime importance in determining 

 the distribution of the vegetation. Only 15 species of seed plants and three 

 ferns are found upon the island, but the moss and lichen floras are compara- 

 tively rich, with 99 and 58 species respectively, of which 46 and 24 respectively 

 are endemic. 



The principal plant associations are the tundra, the swamp and the tussock 

 grass. The tundra has by far the most extensive development, showing all 

 transitional forms from one rich in grasses to the moss-lichen carpet. The 

 swampy places are dominated by Juncaceae, while the halophilous Poa flabel- 

 lata tussock-grass association fringes the beach. It is often almost pure, the 

 tussocks attaining a height of 1.5 m., with an equally great diameter. This 

 association was formerly more widespread and equally important in the Falk- 

 land Islands, 22 but has been disturbed and largely destroyed by the introduction 

 of sheep. 



These islands have a comparatively mild climate of insular type. The 

 summer mean temperature is io° C, the winter mean 2^5 C, affording a fairly 

 well marked periodicity, especially in the flowering of the seed plants, although 

 the 73 cm. of precipitation are very evenly distributed. In portions of the 

 islands there is little snow, and the soil is never frozen hard, but, apparently 

 because of very high winds, there are no trees. Nevertheless, 47 of the 162 

 species of vascular plants are evergreen. The possible land connection with 

 the mainland during the Tertiary may account for 82 per cent of the species 

 being Magellan plants; 15 species are endemic. Skottsberg decides that the 

 vegetation, because of its close peat-forming character, is really a heath, ex- 

 hibiting many characters in common with the heaths of northern Europe, and 

 particularly with that of Faeroes, although with grasses forming a more con- 

 spicuous element. The most widespread association is that dominated by 

 Cortadcria and other grasses, largely of tussock habit. It seems to occupy 



21 



Skottsberg, C, The . vegetation in South Georgia. Wiss. Ergeb. Schwed 



Sudpolar. Exped. 1901-1903. 4: Lief. 12. pp.36, pi. 6 and map. 1912. 



22 , Botanische Ergebnisse der schwedischen Expedition nach Patagonium 



und dem Feuerlande 1907-1909. III. A botanical survey of the Falkland Islands. 

 K. Svensk. Vetensk. Handl. 50: 129. pi. 13 and map. 1913. 



