SPROUTING PROCESS 11 



for food (Figs. 4-8) for the young plant; but they may also 

 have a third function, that of absorption, as illustrated by the 

 germinating corn. (Fig. 4.) In the corn the single cotyledon 

 has been so modified that it serves as a special organ (known as 

 the scutellum) through which the food passes from the endo- 

 sperm of the grain to the embryo. The pea (Fig. 6) and 

 numerous other seeds never raise their food-laden cotyledons 

 above ground, but draw the nourishment directly from them, 

 or through them from the surrounding parts of the seed. In 

 the bean, squash and related plants, the cotyledons serve for 

 storage and also as first leaves for a short time. The cotyledons 

 of the squash (Fig. 7) persist for a much longer time than those 

 of the bean (Figs. 5 and 8) and show their leaf -like character 

 much better. The cotyledons of the castor bean (Fig. 3) serve 

 first, for the absorption of the stored food and, later, as the 

 first leaves. It is very evident that in most plants the leaf, 

 characters of the cotyledons vary in proportion as they serve 

 for foliage or for storage. However, it should be remembered 

 that their leaf characteristics vary somewhat from those of the 

 leaves which are formed later. 



The very rapid sprouting of seeds is partly due to certain 

 peculiar substances known as enzymes or ferments. These sub- 

 stances are usually produced inside the cells and serve to digest 

 or make soluble or otherwise modify the food which is stored 

 within the seeds, thus making it available for the young plant. 

 Probably the most important of these ferments is known as 

 diastase, an enzyme which changes the starch into sugar in 

 very much the same manner as the ptyalin of the saliva in our 

 own mouths changes starch into sugar. The starch is only 

 slightly soluble in water, but the sugar is readily soluble and 

 therefore becomes an important factor in plant growth. 



By the time the supply of stored food is exhausted the young 

 plant has a fairly well developed root, stem and leaf system 



