1907.] DISCUSSION. 225 



trouble. In that case it is pretty hard, after the blight is 

 started, to stop it by spraying. It is always best to begin 

 early. 



Mr. Beach. Do you find that the spores are likely to be 

 carried over in the fall in the land ? Is a piece of land where 

 the blight has been discovered more likely to be badly affected 

 with the blight than a new plot ? 



Prof. Clinton. That I cannot answer definitely, because 

 that point is one in the life history of the fungus, that I am 

 studying to try to find out. These spores will die in dry, hot 

 weather, and they would not, under any condition, live over 

 the winter, that is, theoretically. These fungus spores, how- 

 ever, are not destroyed, for, apparently, they did live in the 

 old dead vines, or in the old tubers. 



Mr. Beach. I was interested in what Professor Clinton 

 might say bearing on that question, because in my experience 

 I had an instance where it seemed to be shown that it lived 

 over two years. I had a field that had potatoes on it two years 

 ago. The field lapped over into an adjoining one where, so 

 far as I know, potatoes were never grown before. This par- 

 ticular year we put two lots under cultivation. We sprayed 

 about the 20th of July thoroughly over the whole of it. In 

 about ten days I was planning to spray again, but delayed a 

 little to get a dry day, and apparently I delayed a little too 

 long, for in going over the field the second time I noticed 

 where the blight was much more severe than it was on the 

 adjoining area where no potato crop had been raised before. 

 That difference continued for the rest of the season. 



Prof. Clinton. Two years ago I imported some potatoes 

 from Colorado. They do not have the blight there. I 

 planted them on a piece of land that had had no potatoes on it 

 for a number of years. What I wanted to find out was if I 

 could get tubers that did not have the blight and plant them 

 on land that did not in order to see if I could get a crop that 

 Agk. — 15 



