CHAPTER IV 

 THE ROOT AND THE SOIL 



WITH the out-door cultivator, the part of the plant 

 environment that lies beneath the soil surface is more 

 under control than the part that lies above it. He can 

 do little to change the composition or temperature of 

 the air or the amount of sunlight; he may do much to 

 influence the fertility, the texture, the drainage and the 

 aeration of the soil. A knowledge of the roots of plants 

 and of the soil in which they grow and feed, is, therefore, 

 of the utmost practical importance. 



86. Functions of the root. The roots of land plants 

 serve to anchor the plant in the soil, enabling the stem 

 or stems of erect species to grow upright, and to supply 

 the plant with water with its dissolved food materials 

 (62). 



87. Origin of the root. The root originates in the 

 stem. As we have seen, the primary root develops from 

 the lower or "root-end" of the hypocotyl (44). But 

 lateral roots may develop freely from other parts of the 

 stem. If we examine the base of the stem of a plant of 

 Indian corn a few weeks after planting, we may see that 

 the main roots start above the point at which the stem 

 was originally attached to the seed ; and if we pull up a 

 pumpkin vine or an untrellised tomato plant late in sum- 

 mer, we often find it rooted from the stem at some dis- 



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