64 



THE PRINCIPLES OF AGRICULTURE. 



undisturbed contact with the soil. In some cases the tip 

 of the root is provided with a kind of cap, or shield, to 

 protect it from injury as it forces its way through the 

 soil. 



The Number and Extent of Roots. The process of sub- 

 dividing and multiplying small roots goes on to a greater 

 extent than is generally supposed. 

 .Rich soil in the vicinity of the 

 roots of some plants becomes com- 

 pletely filled with hair-like root- 

 lets. Sometimes these are so 

 small as to require the aid of a 

 microscope to detect them. 



When a plant is pulled from 

 the soil, these fibers are mostly 

 broken off, only the larger roots 

 remaining attached to the stem. 



The entire length of all the 

 roots of a plant is sometimes 

 almost incredible. In the case of 

 barley, oats, and wheat, growing 



Hairs and root-cap (a), magni- j n r j c h, mellow Soil, it lias been 



found that the total length of all 



the roots of one plant will amount to from one hundred 

 to one hundred and fifty feet. 



Under favorable conditions, roots sometimes descend 

 to a great depth. In deep, mellow soil, the roots of most 

 agricultural plants reach a depth of several feet. The 

 roots of Indian corn, which in common soil do not extend 

 more than two or three feet below the surface, have been 

 known to penetrate into the earth to a depth of fifteen 

 feet. Clover roots have been traced to a depth of eight 

 feet. 



Extremity of a Rootlet of 

 Maple. 



