MERISTEM. 



55 



to be an elongated (prosenchymatous^ element possessing granu- 

 lar protoplasm in which lies a very elongated fusiform nucleus. 

 The wall of the element is very thin at first, but a cell 

 which has just been formed on either side by the division of 

 a cambial element soon undergoes modification into a xylem or 

 a phloem element, the wall being then thickened and otherwise 

 altered (see Chap. v.). In dividing, there are usually only one 



mdj 



rnd, 



Fig. 39.— A Longitudinal Section in the Rbqion of the Intee- 

 rASCicuLAR Cambium of the Stem of Piivus.—x, Cambial cells ; 

 y, young sieve-tubes ; b, bast-fibres ; t^, t^, young wood-elements 

 (traeheides with "bordered pits"); m, medulla; ind^, ground- tissue 



rays. 



or two lines of cells forming active cambial elements. Supposing 

 (see Fig. 38) that there is one such line of cells, c^, and that this 

 line of cells has already produced the elements c^ and Cg, then 

 it is found that the original line c^ remains active, c^ and c. 



