26 



secluded stems, whereas when these plants are not crowded the sun- 

 light has an opportunity to penetrate to the stems and they are not 

 attacked by this fungus. This indicates that the Drop is, in some 

 instances at least, associated with abnormal conditions in plant 

 development. The close growth of lettuce to the soil is quite nor- 

 mal to it, although it is probable that the more delicate stems which 

 result from the modern forcing method render lettuce slightly more 

 susceptible to the Drop than when grown under conditions where 

 less forcing is resorted to. The method of surface sterilization and 

 total sterilization are the only methods at the present time found 

 worthy of consideration, unless we resort to the method of com- 

 pletely changing the soil in the houses, which would be expensive 

 when one has a large range of houses to care for. There is a 

 material reduction in the amount of disease by using one or two 

 inches of sterilized soil upon the surface of the bed. -This method 

 has been tried for two years by one of the largest and most success- 

 ful growers in this state with practically the same results which we 

 have obtained here. 



The hot water method just described has been employed by Hit- 

 tinger Bros, of Belmont, Mass.. whose area of lettuce soil under 

 glass may be reckoned by acres. This treatment is quite efficient, 

 and would probably work better on coarse soils such as Arlington 

 than on tine soil, on account of differences in their water retaining 

 capacity, especially if transplanting takes place immediately after 

 treatment, inasmuch as we found that our plants were stimulated too 

 much by the saturated soil. Another grower who had experienced 

 a loss of about 25% from Drop treated his house with hot water 

 heated by means of steam in a barrel and poured on the soil with a 

 pail. It took a man 3 days to treat a house 256x50 feet, decidedly 

 beneficial results being obtained. While the results obtained from 

 this surface sterilization method are encouraging, in our opinion the 

 troublesome details connected with their constant repetition make 

 such a method in the end much more expensive than complete steri- 

 lization of the soil. This has already been accomplished on a large 

 scale by some growers. In one instance two houses 225 ft. by 30, 

 and 125 ft. by 20 ft. respectively, have been tiled and subjected to 

 steam heat with the result that the two crops following this process 

 were stated to be the best ever obtained. The tile, however, were 

 not placed to the best advantage in this trial ; the two inch tile were 



