14 



Elementary Principles of Agriculture 



sorbed by the root is first taken in by the root-hairs. 

 The seedlings may be growing in soil so dry that water 

 may not be pressed out of it, still, the soil particles are 

 covered with a film of moisture from which the roots 

 absorb their supply. (See Fig. 39.) 



23. How the Root Grows. The root grows only at the 

 tip. The tip does not grow straight through the soil, 



Fig. 13. Diagram of a portion of soil penetrated by root-hairs, h, h f , arising 

 from root, e. At z, s, s' the hair has grown into contact with some of the 

 soil particles, T, which are surrounded by water films (shaded by parallel 

 lines). After Sachs. 



but bends to and fro in a sort of circle, taking 

 advantage of the small openings between the soil par- 

 ticles. It is covered with a delicate root-cap. As the 

 root lengthens, the cells of the cap are rubbed off, but 

 new ones are formed to take their place. Only the region 

 in front of the root-hairs has the power of lengthening. 

 (Fig. 14.) 



24. Absorption of Water by Seeds. Seeds absorb 

 water from the soil particles. When dry seeds are placed 

 in a bed of moist sand or loam, the little film of moisture 

 that covers the soil particles is absorbed by the seeds. 



