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 tnuscipula). Insects are captured 
by the rapid closing together 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- 
