40 PRINCIPLES OF PLANT CULTURE 



If we could remove some of the dissolved aniline blue 

 from the water in one part of the glass, it would follow 

 that the dissolved aniline blue would move from the 

 other parts toward this point, and if the removal were 

 continuous, slow currents would move in this direction 

 from all other parts of the glass. 



We may now understand how the materials from 

 which the plant is built up are distributed to its dif- 

 ferent parts. The water absorbed by the root-hairs 

 (100) is not chemically pure, but holds in solution small 

 quantities of various soluble matters contained by the 

 soil, some of which are used by the plant in growth. 

 As these useful matters are removed from the water of 

 the cells, to be formed into food (58), the supply is re- 

 plenished from the soil, not through any power of selec- 

 tion possessed by the plant, but in accordance with the 

 law of diffusion. In like manner, the food formed by 

 the chlorophyll (58) finds its way to the growing parts. 

 Soluble matters not used by the plant are not taken in 

 to the same extent as those that are needed, because their 

 distribution is less disturbed. 



The distribution of soluble matter in the plant is also 

 promoted by transpiration (74). 



THE INNER STRUCTURE OF THE PLANT 



Thus far, we have considered the plantlet mainly from 

 the outside. Before going farther, it is well to learn 

 also something of its inner structure. We have seen that 

 all parts of the plant are made up of cells (12) and that 

 these cells differ in form and office in the different parts. 

 The cells of the leaf, for example, are different in shape 

 and in the use they serve to the plant, from those of the 

 stem, flower or fruit. 



