35 Introduction to Botany. 



withstand very low temperatures, even at the height of 

 their vegetative condition, is of particular interest, for it 



FIG. 191. 



Helianthemum vulgare. L, the lowland form ; M, the mountain form ; both rather 

 less than one-half natural size. After BONNIER. 



suggests the almost limitless possibilities of modification 

 wherever necessity urges with penalty of extinction. 



