MOORLAND PLANTS 217 



examples could be quoted of Heaths and moorland 

 Grasses in which it becomes insignificant in comparison 

 with the exposed outer surface, which is rendered 

 impervious by its dense cuticle. 



Crowberry seems then to furnish a simple case 

 of adaptation to a particular contingency of moor- 

 land life, viz., summer drought. The adaptation 

 appears less interesting, perhaps, because it seems 

 so obvious. We may think that we could have 

 devised such a mechanism ourselves. But we have 

 not yet got quite to the bottom of the question, and 

 I fear that it will grow darker as we proceed to 

 accumulate facts. The problems of Nature are seldom 

 ridiculously easy. 



It will occur to those botanists who have gathered 

 Andromeda or the Cranberry that these plants are 

 little liable to drought. Crowberry and the Cross- 

 leaved Heath often grow on sandy slopes or among 

 stones, where in dry weather there is no visible 

 moisture. In summer heats there are few drier places 

 than moorland ridges. Being high, they receive no 

 water from rivulets, but only direct from the sky ; there 

 are no deep alluvium, no matted grasses, no over- 

 hanging trees to keep in the water of the soil. The 

 wind blows constantly, and parches the soil still more. 

 But the moors are not altogether dry. They are 

 traversed by hollows, perhaps with a floor of boulder- 

 clay or shale, and these are often choked with 

 Sphagnum moss, which cuts off the natural outlet. 

 In such hollows no summer heat, no east winds ever 

 suffice to dry the soil, and these are the favourite 

 haunts of Andromeda and the Cranberry. Yet 



