94 



THE OAK 



forming an almost continuous ring (fig. 24, se.pli), and 

 consisting chiefly of the sieve-tubes and cells developed 

 from the cambium cylinder, the small primary phloem 



c.caw. 



IG. 24. Transverse sections (semi-diagrammatic) of roots 

 of oak, to be compared with fig. 7. The smaller figure, 

 above, shows the cambium ring, cam, now developed as 

 a continuous layer running inside the primary phloem, 

 pr.pti, and outside the primary xylem, pr.x ; and the 

 larger figure shows the results of its activity in the 

 formation of secondary phloem, se.ph, inside the primary, 

 and secondary xylem, se.x, between the primary xylem 

 groups. In both cases, ep, piliferous layer; c, cortex; 

 P, pith ; sh, endodennis. Within the latter lies the 

 pericycle, in which the cork cambium, c.cam, is now 

 developed. 



