DIVISION OF BOTANY. 



G. E. Stone and R. E. Smith. 



The Rottino- of Greenhouse Lettuce. 



For the past five years this Division has been carrying on contin- 

 uous investigations upon the growth of greenhouse lettuce, with par- 

 ticular reference to the troubles or diseases with which the growers 

 of this crop have to contend. Frequent reference has been made to 

 this work in our annual reports, but no systematic account and no 

 definite results or conclusions have yet been given. The problem 

 has proved to be of so complicated a nature as the investigation 

 proceeded that it has been impossible to arrive at fixed conclusions 

 except by observation and experiment on a large number of 

 crops, together with a considerable amount of laboratory work. 

 For this purpose seven crops of lettuce have been, grown 

 in our own house, each comprising experiments which have sug- 

 gested themselves from time to time. Besides this we have been in 

 communication with several of the largest lettuce growers in the 

 State, visiting their establishments and exchanging suggestions with 

 them, and by this means much valuable information has been 

 obtained. The experiments of the past winter have brought the 

 work to such a point of completeness that we now feel able to pub- 

 hsh our observations and conclusions in definite form. 



It is not the intention of the present bulletin to present the 

 technical side of these investigations, although much of the work 

 has been of that nature. One of the writers has already published 

 (Botanical Gazette 29: 369. June, 1900.) an extended article on this 

 subject, to which reference may be made by those wishing a more 

 detailed account of that portion of the work which deals with the 



