56 THE PLANT CELL. 



going to form permanent elements of the xylem and phloeni. 

 Occasionally, however, several lines of cells may be active. 



In the division of a cambial cell the nucleus probably divides 

 en inassfi (amitosis), and does not undergo mitotic division, a 

 process which would take too long a time for its completion. 

 The elongated fusiform shape of the nucleus is also further 

 evidence of its mass-division. 



Note. — The cambium may be studied by taking transverse and longi- 

 tudinal sections uf any quickly-growing dicotyledonous or coniferous stem 

 or root ; in some roots — e. g. , Horse-radish — the cambium may appear to 

 form a rather wide zone on account of the absence of any great amount 

 of thickening in the elements just cut off on either side. For staining 

 cambium, fuchsin and haematoxylin are good stains to use, the protoplasm 

 being stained by the fuchsin and the nuclei by the logwood. The tissue 

 used for studying cambium should, if good preparations are required for 

 keeping and demonstration, be first fixed with Flemming's solution or 

 2 per cent, solution of chromic acid. Suitable plants for studjring this 

 layer are Riciniis (stem), Horse-radish (root), Pimis (stem or root), and 

 Cuciirhila (stem). 



