miscellaneous: stimuli underlying tumor-formation 525 



Fig. 394*. — Well developed intumescences which formed under lenticels on a 

 silver spotted begonia that was painted with Squibb 's petrolatum April 19 and 

 22, 1920. Photo. May 20. X 2. 



photographed March 24, X 5: (IC) A ridge of callous tissue from the cambium 

 region, also small nodules. (2) At S stunted shoots pushing from a cambium, 

 and at either side hyperplasias rupturing through the cork. (3) Small tumor at 

 X bursting through the cork, at F a naked small nodule. (4) Same as 1-3 but 

 sealed in February 8, 1919, unpared and photographed March 29. Small hyper- 

 plasias rupturing through the original tough cork layer. 



