FLOWERS OF THE MOUNTAINS, HILLS, 

 AND DRY PLACES 



Mountains and hills are essentially caused by the major folds in the 

 crust. They exhibit, exposed at the surface more usually than not, the 

 rocks themselves, upon which in the same way are based the subsoils 

 and soils of more lowland districts, whose derivation is not so obvious. 

 A mountain or hill being based upon a physical character, though in 

 itself independent of questions of soil, essentially tends to cause the 

 plants growing on it to be adapted to dry- soil conditions as xero- 

 philes, for the drainage is thereby at once modified. So that this group 

 consists largely of xerophiles, with others that grow in moist hollows 

 and are not xerophilous. 



A natural classification divides such plants into Lithophytes, or 

 plants growing on bare rock surfaces themselves (chiefly Cryptogams), 

 and Chomophytes, which grow on hills, &c., or rocks with a covering 

 of detritus or subsoil. Of the last are those that grow on the surface 

 (Exochomophytes), and Chasmophytes (crevice plants), which grow in 

 the crevices of rocks, vertical or horizontal. Those here considered, 

 surface plants, are members of the Mesophytic associations driven to 

 higher ground for one reason or another, which by virtue of their 

 position are mainly xerophilous. 



A change can be often noticed in the character of the common 

 plants that have a wide range geographically and also altitudinally as 

 we study them in different habitats. For in the hollows a ubiquitous 

 plant like Dandelion is luxuriant in growth with broad leaves, and in 

 wet meadows the leaves are still more broad, but upon the hills the 

 foliage is much more divided and the whole plant adapted to a xero- 

 philous habit, though not provided so definitely with those characters 

 that stamp Xerophytes. Here a physiographical cause may be seen to 

 act in such a way as to bring about a difference in vegetative character- 

 istics. This is only one of the features that are induced by a retreat to 

 a highland habitat, and it must be remembered that the glacial plants 

 were driven to high ground on the retreat of the ice-sheets. 



