Double Adaptations 437 



horticulture under tlie varietal name of Hede- 

 ra Helix arborea. 



Manifestly this classification is as nearly 

 right as that of the two varieties of the water- 

 persicaria. Going one step further, we meet 

 with the very interesting case of alpine plants. 

 The vegetation of the higher regions of moun- 

 tains is commonly called alpine, and the plants 

 show a large number of common features, dif- 

 ferentiating them from the flora of lower sta- 

 tions. The mountain plants have small and 

 dense foliage, with large and brightly-colored 

 flowers. The corresponding forms of the low- 

 lands have longer and weaker stems, bearing 

 their leaves at greater distances, the leaves 

 themselves being more numerous. The alpine 

 forms, if perennial, have thick, strongly de- 

 velojDed and densely branched rootsticks with 

 heavy roots, in which a large amount of food- 

 material is stored up during the short summer, 

 and is available during the long winter months 

 of the year. 



Some species are peculiar to such high al- 

 titudes, while many forms from the lowlands 

 have no corresponding type on the mountains. 

 But a large number of species are common to 

 both regions, and here the difference of course is 

 most striking. Lotus cornicidatus and Cala- 

 mintha Acinos, Calluna vidgaris and Campa- 



