MAP. I] TIIK F0R:\IATI0NS i6i 



ypc, the characteristics of wliich are exactly repeated on the same 

 <inds of soil so long as the climate is unchanged, whereas the different 

 inds of soil bear different kinds of plants. 77/f comDniuitics of plants 

 w dctenniiicd by the qualities of the soil are teniied foniiations. 



In each formation one species of plant, or a group of species, is 

 iiaractcristic : plants that merely occur sporadically are unessential to 

 he formation, and commoner subsidiary constituents can only give a 

 iflfercnt facies to the formation. Thus, in Europe, we are acquainted 

 ,ith the formation of the beech-forest, where Fagus sylvatica predominates, 

 nd with at least two facies of dissimilar herbaceous vegetation'. If 

 iie composition of the vegetation should alter while the nature of the 

 oil remains unchanged, this is a certain indication of transition into 

 nother climate. A sudden change of formations while the quality of 

 le soil remains unaltered is only found in mountain ranges in relation 

 3 the sudden change in climate. 



Whilst every formation is in its floristic and oecological character 



product of climate and soil, yet the influence of the several climatic 

 nd cdaphic factors is not equal. The influence of the soil is always 

 ilh.rdinate to that of the climatic temperature, whereas under certain 

 onditions that are indeed merely local it neutralizes that of the 

 :mospheric precipitation. Thus woods occur in many spots where the 

 iniate would give rise to grassland, or we maj- find the converse, and 

 gorous forest thrives in patches under a desert climate with a very 

 :anty atmospheric precipitation. Definite properties of the soil may 

 so bring forth a character of vegetation that belongs to none of the 

 imatic tj'pes. These climatic types demand a favourable constitution 



the soil congenial to the vast majority of the plants. Extreme 

 •operties of the soil that are unfavourable to the life of most plants 

 :t vegetation free from the controlling influence of atmospheric pre- 

 pitation. Consequently the vegetation of rocks, gravel, swamps, and 

 her special spots, bears in the highest degree the oecological impress 



the substratum, and this impress for the most part remains identical 

 ider very dissimilar conditions of climatic humidity, which on such 

 lis plays only a subordinate part. 



From \\hat has preceded it appears that tzvo oecological groups of 

 nnalions should be distinguished— the eliniatie or district formations, 

 e character of whose vegetation is governed by atmospheric precipitations, 

 'd the cdaphic or local formations, whose vegetation is chiefly determined 

 ■ the nature of the soil. 



' See p. III. 



M 



