6 4 



PRACTICAL BOTANY 



Sanio's investigations of Pinus, but the main points are the 

 same for Dicotyledons. 



Fig 7, A, shows diagrammatically four radial rows of 

 cambium-cells (i, 2, 3, 4,), as seen in transverse section : of 

 these row (2) is a medullary ray. Note in row (3) the single 



FIG. 7. 



initial cell (z), oblong in transverse section, and the shorter 

 diameter placed radially ; according to Sanio's law of cambial 

 division there is only one such initial in each radial row : from 

 this successive segments (w iv) which go to form wood have 

 been cut off on the inner side, others (b, b, b) which go to form 

 bast on the outer side : each is represented in the diagram as 



