ALPINE PLANTS 199 



should not be kept out of doors the whole winter, provided the 

 woolly plants are kept free from damp. 



There is a very successful Alpine garden in Cheltenham, 

 which consists of a rockery particularly well drained ; the plants 

 are out all the winter, the very woolly ones being covered with 

 glass. They do very well indeed. 



From what has been said, it is clear that the vegetation of 

 moors is chiefly xerophytic. A moorland region is a meeting- 

 place of extremes : its climate consists of intense heat or intense 

 cold, of extreme drought or soaking rain; a moor is often far 

 drier in a hot summer than any ordinary pasture ; the ground is 

 parched and scorched, whilst in winter it is frozen or covered with 

 snow for months. Only a xerophytic vegetation is adapted to 

 such conditions. Even the plants that live in bogs, although in 

 water, appear to be xerophytic in character. Many of them have 

 reduced leaves and a thick cuticle. Clements suggests that those 

 bog plants which appear to be xerophytes at one time lived in 

 xerophytic situations, and not in water. He thinks that Grasses, 

 Sedges, and Rushes are extremely slow in adapting themselves 

 to new conditions, and therefore have retained the xerophytic 

 habit although living in water. In support of this explanation 

 he urges that many of these bog plants have structures which 

 are characteristic of water plants, as, for instance, air passages. 

 He urges, too, the fact that side by side with these bog xero- 

 phytes are found plants which are typical hydrophytes, namely, 

 Marsh Marigold, Water Buttercup, etc., and that the one locality 

 cannot be at the same time suitable to both hydrophytes 

 and xerophytes. He therefore regards apparently xerophytic 

 bog plants as gradually adapting themselves to an aquatic 

 environment. 



Bog plants will be more fully discussed in a subsequent chapter 

 on Aquatic Vegetation. 



The frequent presence of the Birch in the peat of the Heather 

 and Vaccinium moors shows that they have been derived from 

 primitive forest. The same thing has been found in Germany 

 and N. Europe generally, and it is thought by some people that 

 many of the Heather moors in the north of England might be 

 successfully re-afforested, if desired, with coniferous trees. In 



