24 THE OAK 
CHAPTER III 
THE SEEDLING AND YOUNG PLANT 
BrrorRE proceeding to describe the further growth and 
development of the seedling, it will be well to examine 
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 accu- 
rately 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 Jens, or a microscope, 
on the flat face of the almost colourless section. A cir- 
cular area of greyish 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 conveniently regard it as worthy 
of distinction as the piliferous layer (fig. 5, e). 
Similar thin sections a little nearer the tip of the 
