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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 4 
small absorbent cotton wad in the bottom of each tube and adding to 
each one ¢c.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 1x 1x44 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 
Phytophthora infestans growing on lima hean 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, the 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 the cultures were placed for incubation and growth 
in a temperature of about 15° to 16°C. It was found that at this tem- 
