THE CASTOR BEAN 



113 



stem, and there is also a layer of cells on the inner side of the 

 cortex known as the endodermis ; Fig. 53. Within this are 

 the fibrovascular cells fused 

 together and showing little 

 definition into cambium 

 layer or fibrovascular bun- 

 dles. The pith is reduced 

 to a few cells in the center 

 of the root. The tip of the 

 root is always small and 

 delicate, yet it must force 

 its way through the hard 



co, the cortex; 

 ep, epidermis; 

 en, endodermis; 



fb, fibrovascular bundle; 

 rh, root hairs. 



"en ep 



FIG. 53. CROSS SECTION THROUGH 



A SMALL ROOT 



soil. The end of the root 

 contains delicate, thin- 

 walled, growing cells, which 



would be injured in pushing their way. To protect them the 

 tips of the roots aje covered with what is known as the 



root cap; Fig. 54. This is a 

 mass of rather hard corky 

 cells which covers the deli- 

 cate growing cells and pro- 

 tects them from injury as the 

 root pushes its way through 

 the compact soil. 



On the outside of the root- 

 lets, chiefly near their ends, are 

 the most important structures 

 connected with the root, the 

 root hairs; Figs. 55 and 56. 

 They are very delicate threads 

 which grow out of the side 

 of the root and radiate from 

 it into the soil. Figure 56 

 shows a more highly magnified view of some of these hairs, 

 showing that it is a single cell arising from the epidermis of 



FIG. 54. A SEC- 

 TION THROUGH 

 THE TIP OF A ROOT 



Showing the root cap, c. 



FIG. 55. 

 TIP OF A 



ROOT 



Showing the 

 abundance of 

 root hairs. 



