THE CAMBIUM KING. 



133 



either in glycerine or in chlorzinc iodine, the latter perhaps being 

 preferred. The crushed protoxylem (vlp), and the vascular 

 tracheides and vessels nearest to them, are enclosed in an abun- 

 dant thin- walled xylem parenchyma (p). Farther outwards in 



FIG. 49. Cross-section through a young twig of this year's growth of Aristolochia 

 Siphti, showing a vascular bundle after the cambium has commenced its activity, p, 

 parenchymatous elements at the inner extremity of the wood ; vlp, protoxylem ele- 

 ments ; in' and m", pitted ducts ; ic, interfascicular cambium, continued into the fascicu- 

 lar cambium ; r, sieve-tube ; cbp, protophloem elements ; pc, tissue of the pericycle ; 

 sk, inner part of the ring of sclerenchyma-fibres ( x 130). 



the broadening vascular bundle, the vessels increase in diameter 

 (m'}, and have bordered pits. Between them the tissue is thick- 

 ened and lignified ; it consists of xylem parenchyma and narrow 

 tracheides. The cambial-tissue which next succeeds show r s thin- 

 walled flat cells arranged in straight radial rows. This tissue is 



