MATURE OF FOOD STORED IN SEEDS 



which ap h ir like fissures. The starch grains of wheat are of two 

 kinds, very small ones, and quite large ones mixed in with them. 



33. The starch grains are surrounded by a thin coating of 

 cellulose, a substance similar to that of which the cell walls of 

 plants are made. This must be dissolved before the plant can 

 use the starch for food. The plant dissolves it by the use of 

 certain cellulose ferments manufactured by it, and then the starch 

 is dissolved by the diastase ferment (paragraph 180). A similar 

 diastase is present in the saliva of man, but this will not act on 

 the starch grains unless the cellulose coat is broken, or dissolved 

 by some ferment. Heat causes the starch grains to swell. If 

 they are mixed with water, gentle heat changes the grains to a 

 paste. If dry, the cellulose 

 coat is ruptured as the starch 

 swells. Thorough cooking 

 of starchy vegetables and 

 fruits makes them easier of 

 digestion. 



24. Corrosion of starch 

 grains during germina- 

 tion. Since plants cannot 

 absorb solid particles of food, 

 the embryo in the seed can- 

 not use the starch for food 

 until after it is dissolved. 

 The embryo has the power 

 to excrete a juice or ferment 

 (diastase) which acts on the 

 starch grains, dissolving them 

 and changing them to a 



-P. ,, . Cell of endosperm of Indian corn, containing 



SUgar. During thlS process polygonal starch grains, separated by thin plates of 



, . i protoplasm. In the figures a to g, the starch grains, 



the Starch grains become taken from a germinating Indian corn grain, are 



, , m ^ becoming dissolved and disintegrated. After Sachs. 



corroded. To see the cor- 

 roded starch grains, take some of the endosperm of the grain 

 of corn at different stages of germination and examine under 

 the microscope. In comparing the appearance of these starch 



Fig. 25. 



