SECTION III 



THE GROWTH OF THE PLANT 



Introductory. ^When a seed is put into the ground 

 and given suitable conditions it begins to germinate. 

 First the root emerges and penetrates into the soil, 

 after this the shoot grows up into the air. In time, a 

 large branching system of roots is developed in the 

 soil, and, above the ground, a stem with many branches 

 bearing leaves, flowers, and finally fruits. 



It is not easy to say exactly what is meant by growth. 

 It is not simply increase in size and bulk. A sponge, 

 when placed in water, swells and increases in weight, 

 but it has not grown, and, when taken out of the water, 

 it shrinks to its original size. Growth necessarily im- 

 plies a permanent change in form and can only take 

 place in living things. 



It has aheady been seen that two processes are con- 

 tinually going on in the plant, one building up the 

 tissues and the other breaking them down. Growth 

 takes place when the process of building up is greater 

 than that of breaking down. 



In order to study the elementary conditions and 

 phenomena of growth a large number of seedlings at 

 various stages are required. 



Useful seedlings for the purpose are those of the 

 broad-bean, French-bean, giant-sunflower, and Indian 

 corn. These are all large seedlings and can be grown 

 . satisfactorily indoors. 



The Germination of the Seed and the Growth of 

 the Seedling. — The morphology of the growing seedling 

 is well and fully described in most elementary text- 

 books of botany. This section will therefore be con- 

 si F 



