A STUDY OF LEAVES. 15 



through little mouths in the blade called stomatce, 

 which open in moist air and close in dry. 



In studying the blade we consider its veins, 

 base, apex, margin, and surface. 



The veins form the framework, just as the bones 

 constitute the skeleton of the human body. The 



WL- Mid-vein. 



largest one, in the center, is the mid-vein. Branches 

 from the mid-vein are veins ; branches from the 

 veins are veinlets ; and from the veinlets are veinu- 

 lets. The green tissue between the veins is called 

 the parenchyma. Sometimes the parenchyma is so 

 fleshy that the veins are hidden in it. 



