CHANGES IN THE STORED FOOD 93 
Germinative Processes 
Seeds need water, oxygen, and warmth in germination because 
upon these external factors the internal germinative processes 
depend. For dissolving and transporting foods water is indis- 
pensable; the occurrence of certain chemical processes depends 
upon oxygen; and in order for both chemical and physical proc- 
esses to be suitably active, as previously shown (page 90), 
warmth is required. 
Changes in the Stored Food. — The first of the germinative 
processes has to do with the digestion and translocation of the 
stored foods. Whether stored outside of the embryo or in the 
cotyledons, the stored foods, until brought nearer, are beyond 
the absorptive reach of the cells of the plumule and radicle where 
they are most needed. But unless foods are in solution, which is 
the only form in which they can pass through the walls and proto- 
plasm of cells, they can not move from one region of a plant to 
another. Therefore, since starch, fat, and protein, which are the 
chief storage foods of seeds, are not readily soluble in water, they 
must be changed to sugar, fatty acids, peptones, or other soluble 
forms before being transported. However, this digestive process 
occurs not only in seeds but also in all plant regions where foods 
are transported, and also in animals it has its likeness in the diges- 
tive process by which foods are made soluble, so that they can 
pass through the walls of the alimentary canal to the blood, which 
carries them in solution throughout the body. Both the digestion 
and transportation of the stored foods are quite noticeable during 
the germination of some large seeds, as in case of Corn in which 
the endosperm becomes watery and disappears as germination 
proceeds, or in case of Beans where the cotyledons in which the 
food is stored gradually shrink as the young plant develops. 
The digestive process in plants as well as in animals is per- 
formed by special substances known as enzymes, which in case of 
the seed are secretions of the embryo. Enzymes occur in solu- 
tion, either dissolved in water or in protoplasm, in all parts of the 
plant where they either initiate or hasten chemical changes. 
They are exceedingly important substances because upon them 
the majority of chemical changes in plants depend. They are 
specific in their action, that is, as a rule, each enzyme acts on only 
one kind of a substance, and is concerned with only one or two 
