506 



BACTERIAL DISEASES OF PLANTS 



plugged test tubes sealed in with sealing wax and resting on wet 

 cotton, developed glistening ridges or hummocks of rounded 

 cells and long hair-like cells (callous tissue) freely, especially in 

 the cambium region of the tubers, also occasionally sprouts, 

 and over most of their surface in course of a few weeks a w^ell- 

 defined cork-layer under which small hyperplasial tumors 

 developed, pushing up the cork and frequently cracking it open; 



Fig. 381. — Ctiuliflower leaf three-fourths hour after exposure to vapor from 

 0.5 cc. strong ammonia water (0.90 sp. gr.) in 10 cu. ft. of air space to show fugitive 

 motthng. 



sometimes also abortive buds developed from these tumors or in 

 their vicinity (Figs. 393, 394). 



The sealed tube experiments were continued for several 

 months and many small tumors were obtained (Figs. 395 to 

 399). The nutrient substances in these small blocks of potato 

 flesh are soon exhausted and the tumors cease to grow, but, if 

 one could feed them, it would seem as if growth should continue 

 for a considerable period, and that some of the tumors would 

 become large. 



When the pared blocks of potato in the sealed tubes de- 



