300 BOAED OF AGRICULTUKE. 



Question. Is it worth while to cover vines here ? 



Dr. FiSHEE. That is an important point, and one to which 

 I have not alUided. Yon will find that grape-vines grown in 

 the way I have suggested will ripen the new wood as 

 thoroughly as white oak will ripen its wood. The grape-vine 

 is just as hardy as the white oak. If it is not ripened, it will 

 winter-kill. If it is ripened, it will not. If you overload 

 the vine, if you attempt to grow so many grapes that you do 

 not succeed in ripening the wood, it will winter-kill. I have 

 not laid down a vine for five or six years, and I have not had 

 a vine killed in that time, except one or two that mildewed. 

 And that leads me to say a word about mildew. Nobody 

 seems to know the cause of mildew. I may as well confess 

 my ignorance at the beginning as afterwards, but perhaps 

 now is as good a time as any to make a suggestion to 

 observers. A number of facts have forced themselves upon 

 my consideration, and my experience in cultivation under 

 glass has given me what appears to be an important proxi- 

 mate cause of mildew. It is a thing which I think has not 

 been investigated by any observer yet. Having the sugges- 

 tion made to me some years ago by a certain occurrence 

 under glass, I have watched the operation of mildew ever 

 since pretty carefully, and so far as I have gone, the theory 

 will stand, but it requires a long time to make it a certainty. 

 I would like to suggest it to other observers, to put them 

 upon the track. My theory, as suggested by those facts, is 

 this : that a leaf developed in a moist atmosphere, is ex- 

 ceedingly prone to mildew at a certain stage of its growth, 

 in a dry one. If the atmosphere is uniformly of the same 

 hygrometric state ; if there is about the same amount of 

 moisture suspended in it all the time, as there is not, un- 

 fortunately, there will be no mildew, as happens in California. 

 But our climate here is exceedingly variable ; one day will 

 be warm, having an average amount of moisture of seventy- 

 five or eighty per cent., with a clear sunshine, and the next 

 day we will have it down to twenty-five per cent, in the same 

 clear sunshine ; the amount of humidity in the atmosphere 

 varies continually between those two extremes. Now, I 

 have noticed that the out-door mildew comes on like this. 

 After a wet June, about the tenth of July, when it makes its 



