66 



COLLEGE BOTANY 



especially in the fleshy roots. The epidermis is a layer of surface 

 cells which give rise to numerous root-hairs or trichomes (Figs. 

 43, 44, 45 and 46). Each root-hair arises from a single epider- 

 mal cell and in fact is an extension or part of the cell. They 

 are very numerous and very rich in protoplasm and are always 

 located in a zone just back of the tip. New hairs are being 



Fig. 45. — Showing attachment of root- 

 hair to epidermis. 



Fig. 46. — Showing relation of root-hair 

 to particles of soil. 



formed towards the growing tip, while those remote from the 

 tip are gradually dying. The living root-hairs penetrate be- 

 tween the fine particles of soil and serve for the absorption of 

 water an.d such other food materials as are dissolved in it. The 

 root-cap is a mass of cells, which covers and protects the under- 

 lying delicate cells as the growth pushes the tip through the soil. 

 It is a part of the epidermal system., and the outer cells are gradu- 

 ally worn off and new ones produced from within. The epider- 

 mal, cells of the very young roots are not cutinjzed, as in the case 



