54 THE STORY OF THE PLANTS. 



have noticed that farmers and gardeners think a 

 great deal about the ground in which they plant 

 things, and very little, apparently, about the air 

 around them. What is the reason for this curi- 

 ous neglect of the real food of plants, and this 

 curious importance attached to the mould or soil 

 they root in ? 



That is the question we shall have to consider 

 in the present chapter ; and 1 shall answer it in 

 part at once by saying beforehand that, though 

 plants do grow for the most part out of the car- 

 bonic acid supplied by the air to the leaves, they 

 also require certain things from the soil, less im- 

 portant in bulk, but extremely necessary for their 

 growth and development. What they eat through 

 their leaves is far the greatest in amount ; but 

 what they drink through their roots is neverthe- 

 less indispensable for the production of that liv- 

 ing green-stuff, chlorophyll, which, as we saw, is 

 the original manufacturer and prime maker of all 

 the material of life, either vegetable or animal. 



Plants have roots. These roots perform for 

 them two or three separate functions. They fix 

 the plant firmly in the soil ; they suck up the 

 water which circulates in the sap ; and they also 

 gather in solution certain other materials which 

 are necessary parts of the plant's living matter. 



The first and most obvious function of the 

 root is to fix the plant firmly in the soil it grows in. 

 Very early floating plants, of course, have no 

 roots at all ; they take in water and the dissolved 

 materials it contains, with every part of their 

 surface equally, just as they take in carbonic 

 acid with every part of their surface equally. 



