PLANTS. 67 



Much could be said about divided leaves, for the 

 varieties are endless, but the common principle 

 underlying all is that the more divisions a leaf has, 

 the more surface there is exposed compared with 

 the mass. Some plants grow, or their ancestors 



THRESHING WHEAT. 



have grown, in locations where there was so niuch 

 competition among the leaves for air and light that 

 a leaf with an entire margin could not secure 

 enough food and energy to carry on the necessary 

 work, so it had to divide its blade to accomplish 

 the result. 



