miscellaneous: stimuli underlying tumor-formation 537 



discovered that intumescences in great numbers (Figs. 409, 410) 

 appeared on the base of some of the shoots both above ground 

 and below, and not only on the older main axis but also on small 

 compensatory side shoots which began to develop as soon as the 

 tops were destroyed. On a critical examination (9 days after 

 inoculation and 5 or 6 days after the tops were killed) these 

 intumescences were found on 14 of the 16 inoculated shoots 

 (13 pots) and there were none whatever on the 17 control shoots 

 (13 pots). The two shoots which did not show any intumes- 

 cences were those least injured by the inoculation and which had 



Fig. 405. — Intumescences (hyperplasias) on a stunted tumefied potato shoot 

 grown from a pared sterile block of potato flesh in a stagnant saturated atmosphere 

 for 10 days in bright light at 28°-35°C. Tube sealed March 28. Front and back 

 view. Photographed April 7, 1919. 



retained a considerable number of actively transpiring leaves. 

 One of the 14 plants bearing intumescences was specially in- 

 teresting in that it bore an uninoculated and uninjured side- 

 shoot arising from the niain stem at the surface of the earth. 

 This shoot, full of green leaves and transpiring freely, bore no 

 intumescences whatever at this time, whereas the green base of 

 the main axis, killed to within 2 or 3 inches of the ground bj^ the 



on Fuller's scale, that is, excessive. Tissues full of starch and oxydizing enzymes. 

 X 5. The acidity of normal potato juice is about + 20. 



B. Same series as Fig. 403, but intumescences more widely ruptured and tip 

 of the shoot asphyxiated. Photographed May 14, 1919. X 5. 



