miscellaneous: stimuli underlying tumor-formation 539 



inoculation and thus suddenly deprived of all its freely trans- 

 piring foliage, was covered with intumescences, even close to the 

 base of the branch. Some days later the branch also developed 

 intumescences especially on its base. All the intumescences 

 on these plants were hyperplasias and they were in all stages 

 of development, from those requiring a microscope for their 

 detection to those well-rounded out and those cracked open. 

 Also in all the cases 

 which I examined the 

 stomata over them 

 were wide open as if 

 in need of air or bur- 

 dened with excess of 

 water. These plants 

 were in 8-inch pots 

 and stood on a cen- 

 tral bed in a large, 

 well-ventilated hot- 

 house cool enough to 



be suitable for cauli- ^ig- 407 -Hyperplasia under a stoma in the middle 

 , , ... of a potato shoot. From s of Fig. 406 



flowers and they did 



not receive an excess of bright light because they were 15 feet 

 from the glass roof and were shaded from the afternoon 

 sun by a tall banana house. The possible effect of the 

 bacillus, which is an acid producer, was tested by cutting 

 off the top of a part of the 17 check shoots whereupon their 

 stubs also developed intumescences but more slowly and 

 much less conspicuously. In this instance, therefore, neither 

 high temperature, nor bright light, nor feeble light, nor a 

 saturated atmosphere had anything to do with the production 



ruptured and unruptured, and each is beginning to die from asphyxiation, as are 

 also the root-tips. Each block stood on wet cotton, and the tubes were kept in the 

 dark at 23°-25°C. The parts of the shoots which did not show the hyperplasias 

 to the naked eye, as at s, did so under the microscope and they were always 

 under stomata (see Fig. 407). Photographed April 14, 1919. X 5. 



