216 



THE SECOND BOOK OF BOTANY. 



into fibres and vessels of various kinds. This is the 

 cambium layer. Outside of this layer, and by a 

 transformation of its outer cells, the bark is formed ; 

 within the circle made by the cambium and by trans- 

 formations of its inner cells wood is produced. 



The narrow end of this woody bundle, which lies 

 next the pith, and is marked T in Fig. 386, con- 

 sists of spiral ducts and thick-walled fibres ; between 

 these and the cambium layer is the true woody re- 

 gion, comprising about half the bundle. It is made 

 up of woody fibre, with annular, barred, and dotted 

 ducts interspersed. The line E.M points to the 

 medullary ray, F to the woody fibres and small 

 annular fibres, VP to large ducts of various kinds. 

 Beyond the cambium we come upon L, the inner 

 bark, or liber, and then follows the outer bark. 



The lower half of Fig. 387 represents a vertical 



FIG. 387. 



section of the woody bundle shown in the upper half 

 of the picture. Observe in the horizontal section the 

 cambium layer, marked c ; the true wood is seen 



