Water yj 



regions, hot or cold. Thus the pine-tree of the north has 

 its turpentine, the eucalyptus of hot, dry Australia its oil, 

 and the acacias of Africa their gums. 



Many trees and shrubs in hot, dry countries are pro- 

 tected also by having either small or very few leaves, or 

 even none at all. 



Where the air is constantly damp, as it is in many 

 parts of the tropics, there the trees may boldly venture, 

 as the plantain does, to spread broad leaves many feet 

 square to the sun, for the water-supply never fails, and 

 the air is not outrageously thirsty, as it is in the desert. 

 But in those parts of Australia where rain is scanty and 

 droughts are frequent, there the leaves are not only small, 

 as we have said, but they, most of them, also protect 

 themselves by turning only their edges, not their broad 

 sides, to the sun; for they have to economize their re- 

 sources as much as possible. This is particularly the 

 case with many species of eucalyptus, some of which turn 

 one leaf-edge to the earth and the other to the sky, or 

 stand eiect, turning one edge towards the stem and the 

 other away from it, in each case exposing themselves as 

 little as possible. Their leaves, too, are for the most part 

 narrow, and so scantily distributed over the branches that 

 an Australian forest has none of the deep shade which the 

 word naturally suggests to us. 



But when the eucalyptus is transported to other lands. 

 Where it has plenty of deep, rich soil, and moisture in 

 abundance, then it puts on more foliage, showing that it 

 was only the dry heat of its native climate which made it 

 so sparing of its leaves. 



Most of the many species of acacia found in Australia 

 go even a step beyond the eucalyptus in the way of econo- 



