48 



BOTANY OF THE LIVING PLANT 



fascicular, and those between them inter -fascicular cambium (i.e. 

 Fig. 25). In woody stems where the strands are closely grouped, 

 this distinction is not so obvious. 



The cambium is recognised by the repeated division of its thin- 

 walled cells by tangential walls, so that radial rows of cells are produced. 

 As there is no limit to the repeated divisions, a great increase of the 

 tissues may be the result The clearest evidence of division is in the 

 centre of each radial row, and it has been concluded from careful 



s 



FIG. 34. 



Cross section through a radial row of 

 cambial zone in Pinus sylvestris, after 

 Sanio. ( x 400.) H =side next the wood. 

 t=the conjectural initial cell. (From De 

 Bary.) 



FIG. 35. 



Tangential section through the cambium of the 

 Elm, showing the elongated form of the prismatic 

 cambium cells. w=the groups of cambial cells 

 forming medullary rays. ( x 100.) 



comparison of many such rows that in each of them there is an ultimate 

 initial-cell, which retains its identity, giving off on the one side cells 

 formative of wood, and on the other cells formative of bast. This 

 has been styled Sanio's law of cambial division (Fig. 34). 



In transverse section each cambium cell appears oblong, with the 

 broader sides facing inwards and outwards, while the narrower run 

 radially (Figs. 23, 25, 33). If a section be taken longitudinally 

 through the cambium in a tangential plane, the cells appear with 

 pointed ends interlocked one with another (Fig. 35). If a radial 

 section be taken, so as to follow one of the radial rows, the individual 



