92 MOUNTAIN AND MOORLAND 



bright pink, bell-shaped flowers, and small red " ber- 

 ries," really little drupes or stone-fruits. Its leaves 

 are woolly on their stalk and margin, and this must 

 lessen the risk of over-transpiration. They remain 

 green through the winter. There is on Scottish 

 mountains a rarer kind of Bearberry (Arctostaphylos 

 alpina\ which ascends to 2,700 feet ; its flower is white 

 and its fruit black. It might well be called a British 

 alpine. Its leaves are unlike those of the other kind, 

 in falling off when the winter sets in. Here it may 

 be noticed that most of the heath plants are ever- 

 greens, in the sense that their leaves last in a green 

 state through the winter and are replaced all at once 

 in spring. This is different from the evergreen con- 

 dition of the Holly and Ivy, for instance, where the 

 leaves are changed as it were piecemeal, a few at a 

 time. 



The evergreen condition is probably the more 

 primitive, the autumnal fall of the leaf being an adap- 

 tation to conditions where the contrast of summer 

 and winter is very marked. In severe conditions it 

 is advantageous that the leaves should fall, for it 

 reduces the surface from which water may be lost, 

 and it helps to bring the plant into a state of com- 

 parative inactivity which makes resistance to the 

 winter easier. And if the old difficulty arises in the 

 mind that there is plenty of moisture in winter, we 

 have to recall the explanation that the soil is cold 

 and that the absorption of water by the roots is diffi- 

 cult at low temperatures. There may be " physiologi- 

 cal drought," as it is called, where there is no physical 

 drought. 



But it is difficult to give any reason why moorland 



