INTUMESCENCES FORMED AS A RESULT OF CHEMICAL 



STIMULATION, 



BY HERMANN VON SCIIRENK. 



GENERAL DESCRIPTION, 



During the winter of 1903, the cauliflowers at the Mis- 



souri 



Botanical Garden were attacked by the crucifer 



mospora parasitica. The plants were sprayed 



Per 



with various copper sprays, to which a small amount of 

 fish glue had been added in order to cause the spray to 



mor 



S 



days after the spraying, a large number of peculiar wart- 

 like structures began to form on the lower surface of the 

 sprayed leaves. A brief description of these structures 

 was presented in a paper 



read before the W 



o 



Association for the Advancement 



and a brief 

 time 



em 



24 



was published at that 

 It was found that these wart-like formations were 

 in reality large swellings produced in the leaves, which re- 

 sembled intumescences, a large number of which have 

 been described from time to time on various plants. 

 Owino- to pressure of other work, further study of these 

 intumescences had to be dropped at that time, and not 

 until recently, with the reappearance of similar intumes- 

 cences formed as a result of spraying cauliflowers, was their 

 study taken up again. As stated before, these peculiar 

 warts appeared on the leaves which had been sprayed to 

 stop the mildew. A careful examination was made of all 

 the unsprayed plants in this particular greenhouse, but in 

 no case were such warts found on unsprayed plants. 



On plate 25 the photograph of a cauliflower leaf is re- 



produced, taken 



om 



a plant sprayed with copper 



•* Exponential figures refer to the bibliography at end of the paper 



(125) 



