ELM STEM 



107 



To gain a clear idea of the process of secondary thickening, the 

 actual form of the cambium-cells and their arrangement must be 

 recognized : as stated above (p. 7), it is necessary, in order to 

 fully realize the form of a cell as a solid body, to cut sections in 

 three directions at right angles to one another : the cambium-cells 



- /' 





FIG. 



have now been seen in transverse, radial, and tangential sections 

 and the results are represented diagrammatically in Fig. 9, A, B, C, 

 which are based upon results of Sanio's investigations of Pinus, 

 but the main points are the same for Dicotyledons. 



Fig. 9, A, shows diagrammatically four radial rows of cambium- 

 cells (1, 2, 3, 4,), as seen in transverse section : of these row (2) 



