CHAPTER XI 

 FOOD FROM THE SOIL 



It is but a very small part of their food after all which 

 plants, generally speaking, draw from the mineral matter 

 of the soil in which they grow; and yet this small quantity 

 is not merely important, but absolutely necessary. It is 

 dissolved by water and gases, and by the action of the 

 plant itself, and is then taken up by the roots, especially 

 the younger, finer roots, and root-hairs, by which it is 

 passed on to the stem, and so is conveyed to every part, 

 not only to branches, leaves, and buds, but also to flowers 

 and fruit. Every part of a plant needs some amount of 

 mineral matter, and the plant cannot obtain it without 

 water, for whether dissolved by the plant's roots or other- 

 wise, it is in each case taken up in very diluted condition; 

 so diluted, indeed, that the water containing it is hardly 

 to be distinguished from ordinary drinking-water. 



The plant could not be sufficiently nourished by these 

 very weak dilutions, especially while it is growing, but for 

 the fact that it is constantly receiving them. 



Perhaps one of the most striking examples of the way 

 in which plants are fed by this very weak food is to be 

 found among the sea-weeds. Many sea-weeds contain 

 large quantities of iodine, which, like the rest of their 

 food, they draw from the sea. With the smell of iodine 

 we are all no doubt familiar; but if we mix one part of 

 iodine with three hundred thousand parts of water we 



114 



