CHAPTER III. 



THE SEEDLING AND YOUXG PLANT. 



BEFORE proceeding to describe the further growth 

 and development of the seedling, it will be well to ex- 

 amine its structure in this comparatively simple stage, 

 in order to obtain points of view for our studies at a 

 later period. For many reasons it is advantageous to 

 begin with the root-system. If we cut a neat section 

 accurately transverse to the long axis of the root, and a 

 few millimetres behind its tip, the following parts may 

 be discerned with the aid of a good lens, or a micro- 

 scope, on the flat face of the almost colorless section. A 

 circular area of grayish cells occupies the centre this 

 is called the axis cylinder of the young root (Fig. 5, A, 

 a). Surrounding this is a wide margin of larger cells, 

 forming a sort of sheathing cylinder to this axial one, 

 and termed the root-cortex. The superficial layer of 

 cells of this root-cortex has been distinguished as a 

 special tissue, like an epidermis, and as it is the layer 

 which alone produces the root-hairs, we may convenient- 

 ly regard it as worthy of distinction as the piliferous 

 layer (Fig. 5, e). 



Similar thin sections a little nearer the tip of the 



