THE AMEErCAN GKAPE MILDEW. 143 



SUMMARY. 



Grapes arc attacked by many i'liiigi and. insects. Fungi form a group of 

 flowcrless plants. Of tlic fungi -we have treated the Peronosjjora viticola in par- 

 ticular and tlio Unciiiula spirf'h's in general; the former the American grape 

 vine mildew, the latter called (Jidium. In order to become better acquainted 

 with them, a list of questions was sent to many of the leading grape growers iu 

 the United States. The literature on the subject, though abundant and scat- 

 tered, is vague and unsatisfactory. 



The P. viticola is one of the microscopic fungi vrhich attacks principally 

 the leaves, showing itself on the under side in frosty patches and upon the upper 

 side as yellowish spots. The smooth, -eaved varieties show it best. It is a deep 

 seated fungus, sending its mycilium all through the tissue of the leaves, having 

 little iirojcctions which penetrate the wall of the grape cells. The asexual 

 spores arc borne on the ends of branching filaments on the surface of the leaves, 

 and germinate by means of zoospores iu a few hours after they are formed. 

 The little motile bodies called zoospores are provided with tv/o cilia, by 

 which ineans they move about, and finding a new place, germinate as ordinary 

 spores and thus establish a new growth, and thereby rapidly spread the disease. 

 The sexual spores are formed within the tissue of the grape leaf, and are de- 

 signed to carry the mildew through the winter, being provided with a thick 

 coat of cellulose. 



The Oidium is a surface feeder growing largely on the young berries and giv- 

 ing a "lioury" appearance to their surface. It has no well defined spots like 

 the Pcronospora, and is not limited to any side of the leaf. The two kinds are 

 often found growing together, and it is, therefore, very difficult to credit each 

 one with its own amount of destructive work. 



Though the Peronospora shows a preference for some varieties, probably all 

 may be subject to its attacks. The hardy, thick leaved varieties, like Concord, 

 Hartford, and Ives are much less troubled than the Diana, Rogers' Hybrids, and 

 Delaware, which are styled thin-leaved and tender. 



For remedy flour of sulphur dusted on with a bellows, even before the mil- 

 dew has made its appearance, and as often afterwards as good judgment will 

 decide. With this precaution, combined with all the conditions of strong, 

 healthy vines, which with a proper selection of varieties, good soil, location, and 

 careful culture, will secure, it is believed, the fruit of the vineyard will continue 

 to be the laborer's liberal reward and the rich man's healthful cheer, 



I was fortunate enough to be with Dr. Farlow at the time he was making his 

 extended investigations with the Peronosjjora viticola which have since appeared 

 iu the Bussey Bulletin, and was often kindly invited by him to notice the vari- 

 ous states and stages pointed out. So that though not having made a complete 

 study of the disease myself, I can claim ocular demonstration to all or nearly 

 all of the structural and other facts herein presented. To Dr, Farlow is then 

 largely due the substance of this paper, and to him I cannot but extend my 

 sincere thanks, I also desire to mention the names of J. B. Moore, Concord, 

 Mass., \V. N. Barnett, West Haven, Conn,, Hanford & Co,, Bristol, Ind., E. 

 Haigh, Jr,, South Haven, E, Bradfield, Ada, N, B. AV'hite, Norwood, Mass., 

 Secretary M. B. Bateham, Painesville, Ohio, Jabez Fisher, Fitchburg, Mass., and 

 our Secretary, 0. W. Garfield, as gentlemen who have especially aided me 

 with material for this paper, and to whom my hearty thanks are herein 

 tendered. 



Harvard University, Seplemher 1, 1877 . 



