CONTROL OP BI.ACKI.e;G DISEASE: OF THE POTATO. 213 



examined with considerable care with the following result 

 expressed in numbers of diseased plants per acre. 

 S5ed tubers untreated. Diseased plants per acre 163 



Seed tubers treated (formaldehyde solution). 

 Diseased plants per acre o 



Examination of other different portions of the field taken at 

 random at both visits indicated that the above represented very 

 accurately the condition of the field as a whole. No diseased 

 plants could be found on any part of the field where treated 

 seed was used. In a -letter received from Mr. Hussey Aug. 29, 

 he stated that he had just observed several full grown plants 

 on the portion of the field where the untreated seed was used, 

 which were just beginning to show the disease but he could find 

 none on the treated portions which were attacked. 



The Porter Experiment. 



Mr. Porter's experiment especially aimed at securing data 

 as to the relative value of careful selection of sound and per- 

 fect tubers as compared with disinfection alone of seed pota- 

 toes just as they come from the bin. The potatoes used, how- 

 ever, apparently did not carry much disease in the beginning, 

 hence the results are not so marked nor so conclusive as might 

 have been the case had the seed tubers been less healthy. Irish 

 Cobbler was the variety planted and the liquid method of disin- 

 fection was used. The plots were examined July 7 and 19. 



In one large field adjoining plots, consisting in all of about 

 one and one-third acres were planted with, first untreated tubers 

 as they came from the bin, second selected, sound tubers un- 

 treated, and third selected, sound tubers treated by soaking in 

 formaldehyde .solution for two hours. The results obtained 

 from the examination of these plots were as follows : 



Seed tubers untreated, not selected. Diseased plants per acre 24 

 Seed tubers untreated, selected. Diseased plants per acre o 



Seed tubers treated (formaldehyde solution), selected. 

 Diseased plants per acre o 



In another field consisting of about 4 acres were three other 

 experimental plots. The first was planted with untreated seed 

 tubers just as they came from the bin. The second was the 

 same as the first except the seed tubers were soaked in formal- 



