16 



Amphigenous or frequently epiphyllous. Perithecia 85-120 /i, 

 dark brown, opake, reticulations small, rather obscure; appendages 

 from 10 or 12 to 20 or more, varying in length from once and a half 

 to four or more times the diameter of the perithecium, colored for more 

 than half their length, frequently septate, occasionally forked, tips 

 loosely and somewhat spirally coiled. Asci ovate, pedicellate. Spo- 

 ridia 4-6. 



Very rare on vines of cultivated varieties of Vitis labrusca in 

 native [American] vineyards. Mycelium very thin, whitish, with very 

 slender flocci, orbicular, not close pressed. Perithecia very minute, 

 scattered, brownish-black, globose. When abundant, this species also 

 destroys the fruit. Schw. 1. c. 



On Vitis aestivalis, V. cinerea, V. labrusca, V. riparia and V. 

 vinifera, Ampelopsis cuspidata and A. quinquefolia. 



This is a very common species, widely distributed throughout the 

 country, from the Atlantic to the Pacific coast. It is the powdery 

 mildew of cultivated grape vines, and there is good reason to suppose 

 that the so-called Oidium Tuckeri of European vineyards is the same 

 thing, without, however, the development of the perithecia. The 

 conidia found with the perithecia in America are indistinguishable 

 from those on European vines in their native regions, and these same 

 European vines grown in this country have both conidia and peri- 

 thecia altogether similar to those on American grapes. If it is true 

 that the European conidia-bearing parasite is really the present species, 

 the non-development of the perithecia in the Old World is a curious 

 biological phenomenon, though similar peculiarities exist in regard to 

 other species of fungi in contrasted regions in our country. 



The plant varies considerably,. but nearly or quite as much on 

 leaves of Vitis as upon this on the one hand, and Ampelopsis species 

 on the other. The name most commonly adopted is U. spiralis, Berk., 

 from the named figure, without description, in Berkeley's Introduction 

 to Cryptogamic Botany, but subsequently described in Grevillea. 

 Prior to the latter, Peck described U. Ampelopsidis, hence this name 

 has been used in some cases for the specimens on both Vitis and Am- 

 pelopsis since these fungi have been recognized as the same species. 

 But there is no reasonable doubt that Schweinitz had before him 

 specimens of this same species, and if so, his neglected name must be 

 accepted. It should be remembered that he worked before the era 

 of the compound microscope, and his description is necessarily meager, 

 but it is correct as far as it goes. 



U. flexuosa, Peck, Trans. Albany Inst. VII, p. 215. 



Hypophyllous. Perithecia large (1 10-125 //), dark, opake, reticu- 

 lations obscure; appendages numerous, 40 or more, about equaling the 



