THE AMEKICAN GKAPE MILDEW. 141 



appear prematurely ripened, having a red color and irregular outline, and "will 

 remain sour, and hard, and worthless." 



Another noted grape grower of the same State, in speaking of tlie Peronos- 

 2)ora, because it is "a fungus attacking the under side of the leaf," says : 

 "Some varieties, like the Concord, Clinton, etc., in which there is no foreign 

 blood, generally escape, while hybrids, so-called, more properly, perhaps, cross- 

 bred varieties, suffer very much, and should there happen to bo two or three 

 bad years in succession, are often destroyed." 



From Connecticut : "Some of the more tender varieties are affected : of these 

 the Allen, Kebecca, Ma=sasoit, Delaware, AYildcr, and Isabella, in the order 

 named, are susceptible. While the Concord, Ives, Hartford, Clinton and others 

 are about exempt. * * * rp^ ^j^^ ordinary observer the grape mildew 

 exhibits discolored patches on the leaf." 



Another has been much troubled with the mildew. "The Isabella, Dela- 

 ware, Kogcrs' Hybrids, lona, and Diana being most susceptible." 



From Michigan again: "I have not been much troubled witli the mildew 

 until last season, when it injuriously affected almost every vine in my vineyard." 



The description of the disease leaves no doubt that it is the Peronospora 

 viticola. From his excellent remarks we should Judge tiiat he had no varieties 

 which are proof against tlie disease. "All choice varieties are liable to be 

 affected." 



From a prominent writer on horticultural subjects in Ohio, I receive the fol- 

 lowing generalizations as regards the susceptibility of grape vines and mildew : 

 "I have not examined at all critically the varieties (or species) of mildew on 

 our vines, but I think there are two, the white or Oidinm and the rusty or 

 Peronospora sort. The former most common on the vines of the European 

 (F. vinifera) and the hybrids (partly European), and the latter mostly contined 

 to American grapes ; but I think I have found tlie Peronospora on foreign 

 grapes, as I am sure I have the Oidinm on American. By request a package of 

 diseased leaves was kindly sent, the contents of which was as follows : "Xo. 1, 

 Allen's Hybrids, partly foreign." This was badly affected with the Oidiiun, 

 and only one small spot of the Peronospora was to be found. "No. 2, small 

 shoots and leaves of Delaware, most often injured by mildew." The Peronos- 

 pora was very abundant on the leaves, and evidently had been at work some 

 time (Sept. 7th). Some of the Oidium was found. "No. 3, leaves of^Rogers' 

 Hybrid; these are also a part foreign." They were badly affected*" by the 

 Peronospora, but no Oidium. "No. 4, leaves of Catawba; not often seriously 

 damaged by mildew." The Peronospora had evidently troubled these leaves 

 quite early in the season, though not to such an extent as in Nos. 3 and 3. 



Farther items of interest in this department of the subject might be gleaned 

 from other letters, but it is evident that the grape growers are sadly acquainted 

 with the grape mildew, and recognize the two leading kinds. As to varieties 

 most affected this is a more difficult question to decide. The strong thick- 

 leaved varieties like the Concord, Ives, Hartford, and Clinton, appear to be 

 less affected, while varieties like the Delaware, Rogers' Hybrid, Diana, lona, 

 and Isabella, which are tender and thin-leaved, are quite susceptible. 



As far as domestic and foreign "blood" is concerned at present the facts 

 are not in sufficient number to warrant any conclusion, as the Peronospora is 

 peculiar to America; the native vines must have been its home, but this does 

 not prevent its doing as well, or even better, on any introduced variety. Abso- 

 lute proof on this point would require the cooperation of a number of observers 



