482 RELATION TO ENVIRONMENT. 



severe than in the arctic region. This is principally due to the 



Fig. 491. 

 Polar tundra with scattered flowers, Alaska. (Copyright by E. H. Harriman.) 



fact that during the summer while the plants are growing they 



Fig. 492. 



Perennial rosette plant from alpine flora ot the Andes, showing short stem. 

 rosette of leaves, and large flower. (After Schimper.) 



are subject to a high temperature during the day and a very low 



