24 SAGACITY AND MORALITY OF PLANTS. 



will do for the cells, and if the soil does not contain 

 these, growth or cell-multiplication cannot take place. 

 Moreover, the cells which build up the structures of 

 the various parts of a plant often require different 

 sorts of materials. Some of these are taken from 

 the atmosphere (the carbon entirely so), and others 

 from the soil. The food-material in the soil, how- 

 ever, is useless until it is dissolved in such a way 

 that the cells can absorb it. Hence, if a plant be 

 kept without water it will die of starvation even in 

 the midst of plenty. Water dissolves most of the 

 mineral salts out of the soil ; these are absorbed by 

 the roots, and employed to build up the tissues of 

 the plant. The function of the roots is to extract 

 such mineral salts out of the soil, whilst that of the 

 leaves is to obtain carbon and oxygen from the 

 atmosphere. 



The tip of the root of any plant is a most 

 wonderful object. If we examine a carefully pre- 

 pared slice of it with a high magnifying power, we 

 not only see the cells which build it up, but also a 

 special set at the tip, forming a delicate sheath. 

 When a root is growing and extending itself through 

 the soil it comes into contact with stones, pebbles, and 

 large grains of sand, all of which tend not only to 

 obstruct, but also to injure it. It is to protect the 

 real tip of the root — whose duty is to find the 

 mineral salts diffused through the soil, and to 

 abstract them — that the special layer of cells com- 



