35 



Diagram VH. Showinjj the relative amount of tlie weekly loss from Drop in a luttuce 

 crop. The figures at the bottom of the diagram represent the number of weeks. Those in 

 the vertical column at the left the number of infected plants. Average of three experiments. 



week in three experiments. The crops in these experiments occu- 

 pied nearly the same amount of time for their maturity, and they 

 represented about the same amount of development when set out, 

 that is they were about seven weeks along from seed, and when 

 transplanted in the house it took them about seven weeks to reach 

 maturity. These observations were made during the time the plants 

 remained in. the infected soil in the house, since previous to this 

 time they had been growing in sterilized soil and were free from 

 disease. Plants started in infected soil might show symptoms of 

 Drop somewhat earlier than those planted in sterilized soil. From 

 the data represented by the curve it appears that the DroiD increased 

 rather slowly at first until the fourth week was reached, when it 

 increased very rapidly, readying its maximum at the sixth week, just 

 previous to the time the crop reached maturity. 



A curve based upon data from one experiment in which the 

 amount of Rhizoctonia was recorded was quite similar, the maximum 

 amount of disease due to Rhizoctonia coinciding with that given in 

 Diagram VII for the Drop. This also seems to be true in a general 

 way in th? case of the Botrytis Rot, 



