94 Report of the Botanist of the 



trol and the plant is likely to be ruined; but if the affected leaf 

 were removed before the disease had reached the stem the plant 

 would be saved. Moreover, the diseased leaves, if not removed, 

 become a source of infection to neig'hboring- plants, particularly 

 when the affected plant dies and decays. Hence, the seeming 

 importance of carrying all affected leaves and plants from the 

 field. 



Briefly stated, the treatment aims at two things: (i) To save 

 plants already slightly affected; and (2) To prevent the spread 

 of the disease by the removal of the causal organism. 



experiments prior to 1902. 



In i8pp. — The field selected for the experiment was one on 

 which the cabbage crop had been practically ruined by black rot 

 the preceding season. It contained exactly one acre, was trape- 

 zoidal in shape and about twice as long as wide. It lay on river 

 bottom land near Phelps, N. Y., on the farm of Mr. David White. 

 The soil was a sandy loam well adapted to the growth of cabbage. 



The plants were of the variety Danish Ball Head, set June 15, 

 ^^ inches apart each way. They were carefully watched in the 

 seed bed and showed no signs of black rot at the time of trans- 

 planting. 



The field was divided crosswise into two equal parts each con- 

 taining one-half acre. On one half-acre all affected leaves were 

 to be removed once a week throughout the season; while the 

 other half acre was to serve as a check. 



On the half-acre to be treated one affected leaf was found July 

 20 and by July 28 there were about 20 leaves with one or more 

 small brown marginal areas of uncertain origin; but the first 

 real outbreak of black rot was noted August 4, on which date 

 the first treatment was made. For each treatment a record was 

 kept of the time consumed, the number of leaves removed, the 

 number of points of infection and the number of plants removed 

 because of disease in the stem. These data are shown in the 

 following table: 



