Lecture XXII. 



183 



shoots above. In fact the number seen in any cross section 

 varies from six to fifteen. The wood of the conducting tract, 

 which is towards the flat surface of the leaf, is placed on the 

 inside of the tract when the latter turns downward in the stem 

 and the bast lies on its outer side. In the leaf the bast lies 

 directly against the wood, but in the stem a thin layer of growing 

 cells the cambium separates the two. 



The tissue of the stem in which the conducting tracts are 



FIG. 53. Pinus silvestris, apex of short shoot, transverse section at the point 

 of attachment of the two leaves, x 58. a, cuticle ; b, epidermis ; 

 d, cortex ; g, endodermis ; i , wood or xylem. 



embedded is called the fundamental tissue. It is limited on 

 the outside by the single layer of cells forming the epidermis, 

 which is continuous over the whole surface of the end parts of 

 the branches, the dwarf shoots and their leaves. The tough 

 outer layers of its outer cell-walls form a nearly impermeable 

 sheet the cuticle coating the whole; this is only perforated 

 by the stomata. Within the epidermis the fundamental tissue 

 is divisible into three regions : (i) Outside the conducting tracts 



