Iv ON PLANT LIFE 151 
INFLUENCE OF SOIL 
The character of the vegetation is of course 
vreatly influenced by that of the soil. In this 
respect granitic and calcareous regions offer 
perhaps the best marked contrast. 
There are in Switzerland two kinds of 
Rhododendrons, very similar in their flowers, 
but contrasted in their leaves: Rhododendron 
hirsutum having them hairy at the edges as 
the name indicates; while in R. ferrugineum 
they are rolled, but not hairy, at the edges, 
and become ferrugineous on the lower side. 
This species occurs in the granitic regions, 
where R. hirsutum does not grow. 
The Yarrows (Achillea) afford us a similar 
ease. Achillea atrata and A. moschata will 
live either on calcareous or granitic soil, but 
in a district where both occur, A. atrata grows 
so much the more vigorously of the two if the 
soil is calcareous that it soon _exterminates 
A. moschata; while in granite districts, on 
the contrary, A. moschata is victorious and 
A. atrata disappears. 
