60 



A TEXTBOOK OF BOTANY 



[Ch. Ill, 8 



cold, and strong winds, — conditions which make transpira- 

 tion excessive. These conilitions prevail in highest degree 

 in arctic, alpine, and desert regions, and there we find the 

 smallest leaves. In our native flora, the same principle is 

 exemphfied in the plants of liogs, which are open cold places, 

 and in the evergreen trees, which have to ^A-ithstand the rigors 



J'ui. 30.— A view in Hawaii, sliowing tho contrast between tall-growing 

 oonipound-leaA'-ed and low-growing .simple-leaved Palms. (From Bailey, 

 Cyclopedia of HorlicuUurf.) 



of winter. Under conditions intermediate l^etween the ex- 

 tremes, the leaves are intermediate in size, as our temperate 

 vegetation as a whole well illustrates. Correlatively, leaves 

 which grow exposed to similar general conditions approxi- 

 mate to a similar size, as well shown in our common deciduous 

 trees, where the leaves of Maples, Oaks, Chestnuts, Lindens, 

 Poplars, and others are not far from one siz(% or at least be- 

 long to the same orikT of magnitude. 



Leaves which are mori)hologically large souK^times lie- 

 come physiologically small by compounding of their Mades to 

 separate leaflets (page IG ; Figs. 32 and 37). The compound- 



