348 FRUITS AND SEEDS 



H. Germination of Seeds. — Germination of seeds is, as 

 you noted, the renewal of growth by the embryo. If 

 certain conditions are present, this renewal of growth 

 occurs in all good seeds. The conditions necessary for it 

 are seed maturity, abundant moisture, suitable tempera- 

 ture, and the presence of oxygen. 



Light, which is so essential to the later stages of green 

 plants, is not necessary for the germination of their seeds. 

 As you have noted (page 86) , the rate of growth is generally 

 greater in the absence of light than it is in its presence, 

 and this applies to the first stages of the seedling as well 

 as to other parts of the plant. For the gradual trans- 

 formation of a seedhng into an independent plant, how- 

 ever, the illumination of its food-making parts is essen- 

 tial. It is their inabihty to obtain proper illumination 

 which is one of the principal causes of the very high death 

 rate among seedlings. Perhaps you have noted the thou- 

 sands of tree seedlings which start up each spring in a 

 forest. Hardly one in a thousand lives even into the second 

 season. It is the shading by older plants which is the 

 principal cause of their death. 



a. Water Cultures. — Soil is not necessary for germina- 

 tion nor is it even necessary for the later growth of' the 

 plant. It is entirely possible to grow plants without soil. 

 They may be brought to maturity, even to the maturity 

 of flowers and fruit, by means of what are called water 

 cultures. With their leaves in the light, and their roots 

 in water that contains in solution those substances the 

 plant needs, some- plants seem to do nearly as well as 

 when growing under natural conditions. Corn, by this 

 method, has been matured through several generations 

 without coming in contact with a single grain of soil. 



