THE FALL OF THE LEAF 



275 



of a botanical garden and laboratory appliances. The 

 results of his vacation studies are given in the 

 Botanische Zeitung for 1860. Mohl discovered the 

 separating layer by cutting sections through the leaf- 

 stalk when the fall of the leaf was imminent. He found 



FIG. 67. Section through leaf-base of Horse Chestnut. X 150 (part of Fig. 66, 

 more highly magnified), -vb, vascular bundle ; s, corky layer. 



it to be a thin layer of living and active cells, travers- 

 ing the cushion. It is charged with abundant living 

 protoplasm, contains many starch grains, and appears 

 in the midst of cells which are almost empty and well- 

 nigh dead. The separating layer can often be picked 



T 2 



