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heretofore by laborious field experiments has taken as many years. The 

 purpose in the trials of 1909 was to determine more fully the reliability of 

 this method and its applicability for comparative trials with a large num- 

 ber of varieties. 



In all, 76 varieties of potatoes, 46 of which Dr. Jones collected in 

 Europe, were tested. Practically all of these were varieties of economic 

 value in their respective localities. Most of the European varieties were 

 of reputed disease resistant qualities. All had been grown on the Vermont 

 Experiment Station grounds under as similar conditions as possible, for 

 four years previous to these experiments. 



The method used was, first, to prepare sterile test tubes by placing a 

 small absorbent cotton wad in the bottom of each tube and adding to 

 each one e.c. of water. The tubes were then plugged with ordinary cot- 

 ton and sterilized in the autoclave. The next step was to place in each 

 such tube a small sterile block cut from a raw potato. Considerable care 

 was necessary to avoid contamination in this process. The work was all 

 done under a transfer hood freshly washed out with corrosive sublimate 

 solution. The potato tubers were first washed then immersed for about five 

 minutes in a corrosive sublimate bath. They were then peeled with sterile 

 knives and the sterile interior flesh was finally cut into several small 

 blocks of such size, about 1 x 1 x 41 cm., as would drop easily into the 

 tubes. These tubes were then held 24 hours at about 22° C, in order that 

 any contaminated tubers might be detected and discarded before the in- 

 oculations were made. The inoculations were made from pure cultures of 

 Phytoplithora infestans growing on lima bean agar and about 15 to 18 

 tubes of each variety were inoculated. About twelve varieties were run 

 in each series, two of these varieties used as checks, being the same in all 

 the series. For these checks Professor Wohltmann and Green Mountain 

 varieties were used because they showed a very uniform growth all 

 through and stood at the two extremes, tlie former being one of the most 

 resistant varieties, the latter one of the most susceptible. 



For each inoculation, a small piece of the fungus was transferred 

 with a platinum needle from the agar to the block of potato and scratched 

 into it to prevent its drying up before infection could take place. If 

 proper care was taken in making this inoculation, a uniform growth was 

 obtained on all the blocks of the same variety. 



After inoculation tlie cultures were placed for incubation and growth 

 in a temperature of about 15° to 16° C. It was found that at this tern- 



