THE STEM. 25 



* 



branches diverging from the collar, as the gooseberry, 

 currant, etc., are called shrubs , or bushes. Where the 

 stem is destitute of branches to some distance from the 

 ground, it is usually called the trunk. 



Different Parts of the Stem. A stem, or branch of a 

 tree, is composed of the following parts, which are dis- 

 tinctly observable when we cut it across. Figure 2 repre- 

 sents a portion of a stem of a young tree, one year old, 

 A , 



CO JS F 



Fig. 2. SECTION OF A STEM ONE YEAR OLD MAGNIFIED. 



A, Bark ; B, Wood ; C, Epidermis ; Z?, Corky Layer ; E, Green Layer ; F, Inner 



Bark, or Liber; (?, Pith; H, Medullary Rays; /, Woody Fibre; K, Dotted 



Ducts ; L, Spiral Ducts. 



so cut as to show a cross section, and a longitudinal one 

 at the same time. The bark, included in the dotted line 

 A, consists of an outer and inner bark. 



The Rind, or Outer BarJc, is composed of three layers. 



1. The Epidermis, or Cuticle (C), which is found only 

 on recent shoots, and the young parts of trees ; this is 

 thin, smooth, and delicate, like tissue paper, and is easily 

 separated from the parts beneath it. Next within this is 



2. The Corky Layer (D), which is usually of some 

 shade of brown or ash color; this, seen through the epi- 



2 



