miscellaneous: stimuli underlying tumor-formation 535 



Fig. 403. — Ruptured and unruptured hyperplasias on stunted shoots of 

 potato grown in dull light at 25°C., in the sealed tubes shown on Fig. 399. Time, 

 18 days. The right-hand block also shows two unruptured hyperplasias below 

 the shoot and a rupturing one at the left. These are pushing through the very 

 resistant cork surface of the tuber. Photographed May 14, 1919. X 5. 



