PLATE 50 



Fig. 1. Portion of the base of the pedicel of Nicotiana at a late stage in 

 the process of abscission showing the independent origin of the process in the 

 pith. 



Fig. 2. Portion of the cortex in the separation layer of Nicotiana showing- 

 separating cells next to the vascular system. 



[422] 



