52 STRUCTURE OF THE ROOT 



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with root hairs for absorption. Within the epidermis is a broad 

 zone of cells, the cortex, often used for the storage of manufac- 

 tured foods, while in the center of the stem are the vascular 

 bundles. The woody portion of the bundle, or xylem, radiates 



FIG. 36. Cross-section of root taken above section shown in Fig. 33: 

 e, epidermis with root hairs; c, cortex bounded on inner side by endo- 

 dermis, end. Within is the central region containing vascular bundles; 

 x, xylem; p, phloem. I. D. Cardiff. 



outward from the center and the soft portion, or phloem, alter- 

 nates with it (Fig. 36, .r, p). The materials absorbed from the 

 soil are largely transported up to the stem and leaves through 

 the xylem, and the foods manufactured by the leaves reach the 

 root by means of the phloem cells. The branches of the root 

 originate in a very curious way from the cells just outside the 

 xylem. These cells by repeated divisions form lateral roots which 

 gradually dissolve the tissues in their way and finally grow out 

 to the surface of the root (Fig. 37). By this arrangement they 

 are provided with a root cap and fully prepared to enter the soil 

 on emerging from the"' old root. 



25. The Transport of Water in the Root. The inner layer of 

 the cortex, the endodermis (Fig. 36, end), consists of a layer of 

 cells which, in the older part of the roots, forms a very compact 



