2 i6 transactions—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
Alpine, and Alpine, has its special characteristics. In the littoral zone, 
salt is the chief factor and man’s influence is at a minimum. The 
lowland zone owes its peculiarities almost entirely to man’s influence 
in agriculture, and little of primitive nature remains. In the sub- 
alpine zone man is still an extremely important agent in the 
changes which he induces through pasturing, game-preserving, and 
forestry, but here much more of the natural vegetation is present. 
The alpine zone is again beyond man’s control, and is determined by 
the prevalent arctic conditions of extreme change. 
This method of subdividing the land according to the predominat¬ 
ing social species is of extreme value in correlating our plant-life with 
that of continental nations. By tracing each association through its 
continental range we see clearly to what part of the general European 
flora each division of our district belongs. From the associations 
we have treated, especially from the Callunci heath association, the 
resemblance between our flora and that of Scandinavia and North 
Germany must have been evident. Kerner (p. 898), in his sub¬ 
divisions of the earth s flora, places the British flora as part of the 
Baltic flora, which also includes Scandinavia, North Germany, and 
West Russia. He uses as his guiding principle the resemblance 
between the social species of these respective countries. 
I add a list of the works referred to in this paper, and of a few 
others which have also assisted in its preparation. This bibliography 
may serve as a guide to the chief papers dealing with the plant 
associations of our region. Further references can be found in 
the works mentioned, especially in those of Warming and Drude, and 
in Engler’s “ Botanische Jahrbiicher.” 
BIBLIOGRAPHY. 
Barclay, William— The Flora of the Woody Island. 
(Trans. Perth. Soc. Nat. Sc. I. (1887), pp. 30-44.) 
Christ, H.—La Flore de la Suisse et ses Origines. 1883. 
Darwin, C.—Origin of Species. Sixth Edition, p. 55. 
Drude, Oscar—Manuel de Geographie Botanique. 1897. 
Engler’s Botanische JahrbUcher fur Sys. Pfl.-gesch. und Pfl.-geog. 
Farquharson, Rev. James.—On Howebottom, the “ Hained Ground” at 
Bowhill, Selkirkshire. (Proc. of the Berwickshire Naturalists’ Club 
1876-78.) 
Flahault, Ch. La Distribution Geographique des Vegetaux dans un Coin du 
Languedoc. 1893. 
Fliche. Un Reboisement. (Ann. de la Science Agronomique, I. 1888. Cited 
from Bull. Soc. bot. France, xxxvi. p. 14.) 
