16 TU£ CHEMISTIiit OP THE FARM 



Another class of seeds, of which Hnseed 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. Some seeds 

 will slowly germinate below 40° Fahr. ; the quickest 

 germination usually occurs between G0° and 80°. 

 Under favourable conditions 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 germina- 

 tion may be easily studied in the ordinary operation 

 of malting barley. 



Seeds buried too deeply in the soil may not ger- 

 minate for lack of oxygen. Or, if germination takes 

 place, the plumule may fail to reach the surface, the 

 store of food in the seed being exhausted before the 

 soil is penetrated and daylight reached. The smaller 

 the seed the less should be the depth of earth with 

 which it is covered. 



Plant Development.— The development of the plant 

 after germination follows a regular coarse. With an 



