PLATE I 
A. —A lettuce plot in the experimental house affected with drop in 1917. The same 
year this plot was treated with a 1-100 formaldehyde solution. Nine crops of lettuce 
have since been grown in this bed without the loss of a plant. 
B. —An untreated plot in the same bed as A and adjacent to it. Ninety-four per 
cent of the plants in this plot dropped. 
