2IO MAINE AGRICULTURAL EXPERIMENT STATION. I9II. 



Seed tubers untreated, selected. Diseased plants per acre 87 

 Seed tubers treated (formaldehyde solution), selected. 

 Diseased plants per acre o 



The Donaldson B-vperimeni. 



Mr. Donaldson planted 270 barrels of seed of which 260 

 barrels were treated by soaking in formaldehyde solution. • The 

 remaining 10 barrels were planted without treatment. 



Where the disinfection experiment was tried Irish Cobbler 

 was the variety planted. The seed was grown on the same field 

 in 1910. In writing to the Station under the date of August 

 15, 1910, Mr. Donaldson stated that on this field he counted on 

 an average about 20 diseased plants per row 60 rods in length. 

 The seed on the main portion of this field in 191 1 was soaked 

 in formaldehyde solution for 2 hours and then turned out on 

 a clean platform to dry before cutting. The cutting was done 

 by hired help but under the o'wner's supervision. Each seed 

 cutter was given directions to discard all tubers which were in 

 any way imperfect, and if by chance he cut a tuber which 

 showed any signs of decay or browning in the flesh to discard 

 it and place the knife he was using in a jar of formaldehyde 

 solution which was provided. Extra knives were supplied so 

 that there was always a sterile knife in the disinfecting solu- 

 tion in case the one in use became contaminated. Air. Donald- 

 son stated that it was practically impossible to hire seed cutters 

 who would constantly observe these precautions and doubtless 

 this may account for the very small amount of blackleg on the 

 main field. 



For the chief experiment one barrel of badly bruised and 

 one barrel of selected seed was sorted out. One half of each 

 lot was cut and planted without treatment. The other half of 

 each lot was soaked for 2 hours in formaldehyde solution after 

 cutting. The advantage of this latter variation from the usual 

 practice of disinfecting before cutting is that much of the 

 chance contaminations of healthy seed pieces while cutting can 

 be overcome in this way. As will be seen later (p. 224) no 

 detrimental results with regard to germination were secured 

 from this treatment. 



The four lots of treated and untreated seed were planted in 

 four rows, each row being equivalent to about one-tenth of an 



