40 BULLETIN 727, IT. &. DEPARTMENT OF AGRICULTURE. 



drainage water also passed through the rows of Cucurbita gourds, 

 none of which became diseased (fig. 14). 



In field 2 all of the rows of interplanted seedlings showed recent 

 and even-aged infection on September 13. Besides leaf and coty- 

 ledon lesions numerous enough to cause these organs to curl up, 

 some seedlings bore girdling stem lesions as well. This infection 

 is likewise attributed to surface drainage during the rains of the 

 week previous. 



That the spores are washed from the leaves to the soil was proved 

 by the tests previously cited. That the spores are carried consider- 

 able distances by the surface run-off during rains and spattered from 

 this drainage water upon all plants along the drainage channel is to 

 be inferred from the observations presented above. 



To test experimentally the latter hypothesis, steps were taken to 

 prove that the spores were present in surface drainage water. On 

 August 14 four glass tumblers were sunk flush with the soil at the 

 points indicated in figure 13, so as to intercept surface drainage 

 water during the next rain. No tests were made until the rains of 

 the first week in September. On the morning of September 5 the 

 traps were emptied. A heavy shower occurred in the afternoon, 

 after which the contents of the four traps were collected in sterile 

 flasks. At the same time samples of the soil near two of the traps 

 were collected. 



Each sample of drainage water was tested by poured plates as 

 follows: Of the drainage water 1 c. c. was transferred to a flask con- 

 taining 99 c. c. of sterile water, and from this 1 c. c. was transferred 

 to a second 99 c. c. flask. Using recorded amounts of inoculum 

 from these dilutions, three plates were poured from the first flask 

 and two from the second in water agar plus 2 per cent dextrose. 

 No colonies of the anthracnose fungus appeared in any of these 

 plates. The soil samples were also tested by the method outlined 

 earlier, and only negative results were secured. 



That spores of the anthracnose fungus were present in the samples 

 of drainage water was proved in another way, however. The con- 

 tents of each trap, after the removal of the sample for plating, were 

 sprayed upon healthy potted cucumber plants. 1 The results of 

 these tests are presented in Table IV. 



Spores of the anthracnose fungus were present, therefore, in three 

 of the four traps. Trap 1 , in which no spores were found, was located 

 near the upper edge of the field, and hence there was a smaller reser- 

 voir of disease contributory to it. 



After the additional rains of September 6 and 7 a series of five 

 plates each was poured from traps 1 and 2 in field 2, and, as in the 



1 These inoculations, as well as those described later, were made by Dr. E. Carsner in connection with 

 his investigation of the angular leaf-spot of cucumber. 



