CHAPTER VI. 



STRUCTURE OF THE ROOT. 



The origin of the primary, or tap-root from the radicle of the embryo, 

 the development of the root-system from it, and the relation of 

 that system to the shoot in the normal Flowering Plant have been 



Fig. 56. 



Diagram illustrating the arrangement of tissues in the transverse section of a root. 

 rh= root-hairs, exod =exodermis. pilif= piliferous layer. ^nrf = endodermis. per — 

 pericycle. #y = xylem. phi — phloem. £=pith. 



described in Chapter I. Its fixation in the soil by means of its root- 

 hairs has also been noted. The details of its structure will now be 

 examined, so that the facts mav serve as an introduction to the 

 study of the functions which the root has to perform. 



The root is typically cylindrical, and accordingly its transverse 



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