MISCELLANEOUS: TUMORS IN ABSENCE OF PARASITES 491 



abnormal elevation of temperature and excessive water sup- 

 ply/' combined with weak illumination. With this view 

 Atkinson agrees. In the last edition of his book Sorauer 



FIG. 368. Cross-section, well above the leaf surface, of acetic acid tumor 

 on cauliflower leaf 7 days after exposure. Surface covered by an epidermis. 

 Block 1289. Fixed September 28, 1916. The exposure was for > hour in 10 

 cu. ft. of air space to vapor from 10 cc. of Carney's fluid on a warm bath (about 

 65C.). 8 mm. obj., 4 oc., bellows at 50, and enlarged Y by engraver. Photo- 

 micrograph by the writer. 



places intumescences under diseases due to "excessive moisture 

 of the air." 



Other observers regard strong light as favorable and specifi- 

 cally on grape leaves (Viala and Pacottet, I. c.) "excess of light in 



