THE CROWN GALL: CAUSE 



431 



FIG. 329. Crown gall confined to the bark parenchyma of a Paris daisy 

 stem but containing tracheids (above A'), induced by needle inoculations % mm. 

 deep. Under and at the left of X there is action at a distance, i.e., large cells 

 like X are dividing as if by a stimulus received from the neighboring hyperplasia. 

 The same phenomenon has been- observed in crown gall on tobacco. (Consult 

 Jour, tancer Research, Vol. I, No. 2, Plate I, Fig. 3, and Plate XXIII, Fig. 78.) 



