GERMINATION. 13 



or germ, which is always extremely rich in albuminoids, 

 fat, phosphates, and potash. It also contains a store of 

 concentrated plant food, intended to nourish the young 

 plant till its root and leaf are developed. In some 

 seeds, as those of beans and turnips, this store of food is 

 chiefly located in the "cotyledons," or rudimentary leaves; 

 in other seeds, as those of the cereals, there is a reserve 

 of food outside the embryo, in the " endosperm." In the 

 seeds of the cereals, and of many other plants, the chief 

 ingredient of the reserve matter is starch. Another class 

 of seeds, of which linseed and mustard-seed are examples, 

 contains no starch, but in its place a large quantity of fat. 



For germination to take place, moisture, oxygen, and 

 a suitable temperature are necessary. Under these con- 

 ditions the seed swells, oxygen is absorbed, a part of the 

 carbonaceous ingredients is oxidised, heat is developed, 

 and carbonic acid evolved. During these changes the 

 solid ingredients of the seed gradually become soluble. 

 The starch and fat yield sugar. The albuminoids are 

 converted into peptones and amides as, for instance, 

 asparagine. These changes are principally accomplished 

 by the agency of ferments (enzymes) contained in the 

 seed. With the soluble food thus formed the radicle and 

 plumule are nourished. They rapidly increase in size, 

 emerge through the coats of the seed, and, if the external 

 conditions are suitable, soon commence their separate 

 functions as root and leaf. The process of germination 

 may be easily studied in the ordinary operation of malting 

 barley. 



Seeds buried too deeply in the soil may not germinate 

 for lack of oxygen. Or if germination takes place the 

 plumule may fail to reach the surface, the store of food in 



