The Nature of Plants 



FIG. 



W. T. Skillino 

 Root hairs on radish seedlings. 



one central root, called 

 a " taproot," more promi- 

 nent than any of the 

 branches, which goes 

 straight down in search 

 of water (Fig. 3). An 

 example is to be seen in 

 the long radish. This 

 root growth may be 

 compared to the top 

 growth of such a tree as 

 the tall, slender Italian 

 cypress. 



The roots serve a double purpose. They furnish 

 anchorage for the plant, and they absorb water and dis- 

 solved food materials. (Exp. 2.) Within the roots 

 there are channels which lead up to the part above 

 ground, but there are no openings in the roots to admit 

 the soil moisture and its burden of dissolved food material. 

 Evidently, then, this moisture must pass directly through 

 the thin outer covering of the roots in order to enter 

 these channels. The older and larger portions of the 

 root are protected by an almost waterproof covering that 

 resembles bark. But the outer layers of the newly 

 started branches on the roots are soft and so let the water 

 pass through. At the tip of each root there is a " root 

 cap," a hard covering that shields the new and tender 

 growth of the root as it thrusts its way among the soil 

 particles. Just back of the root cap is the growing point. 



Near the growing point the root is covered with a mul- 

 titude of small, tubular projections called " root hairs " 



The uses 

 of roots 



How water 

 and food 

 materials 

 enter 



The root 

 hairs 



