86 



THE VEGETATIVE FUNCTIONS OF PLANTS 



enzymes, which have the power of converting insoluble 

 starch, proteins, and fats, into soluble substances. Starch 

 is converted by diastase (one of the earliest known enzymes), 

 proteins by proteases, and fatty substances (lipoids) by 

 lipase. 



Fig. 63. — Venus's flytrap (Dioncea muscipula). Insects are captured 

 by the rapid closing togetlier of the two valves of the leaf-blade. When 

 the valves come together the rigid marginal teeth interlock, making escape 

 impossible. The digestive enzyme is secreted by glands distributed over 

 the surface of the valves. (After John Ellis.) 



Digestive enzymes are probably secreted by every 

 active plant- cell. In the corn grain the corn starch, 

 (endosperm), surrounding the embryo, is digested during 

 germination by diastase secreted by a glandular epithe- 



