248 



THE EFFECT OF TEMPERATURE 



size of leaves has been shown by Stahl* to consist chiefly 

 in a reduction of the leaf surface. Accompanying this 

 there is usually an increase in the thickness of the leaf. 

 In addition to the reduction of size, Scott Elliott t has 

 shown that there may be a considerable change in the 

 form of the leaves, owing to the reduction in the length 

 of the exposed leaves being much greater than the re- 

 duction in the breadth. The accompanying table 

 shows the average ratio of length to breadth in from 50 

 to 100 leaves of various grasses and plants, which were 

 collected in the one case from sheltered and shady 

 places, and in the other from the most exposed and 

 driest spots known: 



* Jenaisck. Zeit., Bd. xvi. p. 102, 1882, and Bot. Zeit., 1880. 

 fProc. Linn. Soc., vol. xxviii. (Botany), p. 375, 1891. 



