PLATE 49 



Fig. 1. Base of pedicel of NicoUana bud showing groove, separation zone, 

 and process of abscission well under way in dorsal cortex. 



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

 bulging of the epidermis, one of the first signs of abscission. 



[420 ] 



