New York Agricultural Experiment Station. 183 



During the next ten days the leaves were kept constantly moist. 

 As no sign of Phytophthora appeared, a second attempt at inocula- 

 tion was made on May 4 by sprinkling the leaves with a soil filtrate 

 prepared as before from soil from one of the boxes containing the 

 remains of decayed tubers and potato stems. This, also, gave 

 negative results. Some of the leaves turned yellow and decayed, 

 but no Phytophthora appeared. The experiment was closed May 16. 

 None of the plants in the open greenhouse showed any indication 

 of Phytophthora either on leaves or tubers. 



Experiment No. 2. This experiment was, essentially, a repetition 

 of Experiment No. 1, though differing from it in some of the details. 

 In October, 1912, seven boxes were filled with soil and rotting 

 potatoes from a field in which late blight and rot had been very 

 destructive. First, a layer of about two inches of soil was placed in 

 the bottom of each box, then a layer of potato stems followed by a 

 layer of rotting tubers, and, lastly, another layer of soil. The boxes 

 were left in the open field exposed to freezing and thawing until 

 January 20, 1913, when they were placed in a greenhouse. Seed 

 tubers known to be free from Phytophthora were obtained from 

 Riverhead, Long Island. After being washed and disinfected with 

 formaldehyde solution these tubers were planted in six of the boxes 

 on February 1. Previous to planting, the soil and decaying tubers 

 and potato stems had been thoroughly mixed. Although some of 

 the decaying tubers still retained their form all were so far advanced 

 in decay that no growth of sprouts was possible. They could be 

 readily pulled apart with the fingers. One of the boxes was placed 

 at once in the inoculation chamber. The plant in this box grew 

 rapidly. By March 19 it had three stalks 20 inches high. The 

 leaves were large and perfect except for some cedematous out- 

 growths along the midribs of some of the leaves. They appeared 

 to be in excellent condition for infection by Phytophthora. The 

 first attempt at infection was made March 19; the second, March 26; 

 and a third on April 1. Each time the leaves were thoroughly 

 coated (some on the upper and some on the lower surface) with thip 

 mud prepared by stirring up the mixture of soil and decaying potato 

 material in a small quantity of water and removing the coarser 

 parts by squeezing with the hands. It was applied with a paint 

 brush. The plant was scarcely ever dry during the twenty days 

 that it remained in the moist chamber. No Phytophthora appeared 

 upon it. 



