140 Alpine Plants. 
best met by the natural properties of a limestone 
soil, and this is also true of the great majority of 
plants which are hairy or downy on leaf or stem. 
If such kinds are to be grown successfully on 
sandstone, it is therefore necessary to simulate these 
favourable conditions as closely as possible, by the 
choice of elevated, sun-burnt positions and a poor 
soil, rough in texture and full of grit. On the other 
hand, another wide range of plants, such as is 
exemplified by many of the Primulas, that only thrive 
when never permitted to become dry during their 
period of active growth, flourish naturally upon 
sandstone or gritstone sites, and if they are to be 
cultivated upon limestone must have partially shaded 
positions and a somewhat retentive but sweet soil 
upon acool bottom, along with a plentiful artificial 
supply of water throughout the dryer months should 
the natural water supply be at all deficient or irregular, 
or should the soluble salts readily taken up from 
limestone or dissolved from it by the rain be injurious. 
From this last cause, the cultivation upon a lime- 
stone soil of plants which are actually limestone- 
hating is rendered so difficult as practically to debar 
from the attempt even when every other circum- 
stance can be rendered favourable. This considera- 
tion finds its most important application in the case 
of plants requiring a vegetable soil, the differing 
relation of which towards the two classes of geolo- 
gical formation already mentioned is far more rigid 
and incapable of adaptation in its bearing upon 
plant-cultivation than is that of the characteristics 
of the one formation to those of the other. 
