17 



diameter of the perithecium, hyaline, minutely roughened, thickened 

 and irregularly flexuous toward the tip. Asci about 10, ovate or pyri- 

 fbrm, strongly pedicellate. Sporidia 3, small, 15-20 /* long. 



On ^Esculus glabra, ^.flava, and jE. Hippocastanum. Ap- 

 parently not common, but reported from New York (Peck), Illinois 

 (Earle), Missouri (Demetrio). 



The species is easily determined by the abrupt, wavy crooks in 

 the outer half of the appendages. 



U. circinata, . & P. Erysiphei of the U. S. in Journ. Bot. 1872. 



Hypophyllous or sometimes amphigenous. Perithecia very large, 

 depressed, 150-225 a in greatest diameter, texture soft, reticulations 

 very small and irregular ; appendages very numerous, slender, simple, 

 about equal to the diameter of the perithecium, hyaline, smooth, tips 

 not swollen, ascending from the upper half of the perithecium. Asci 

 numerous, 14 or more, long and slender, oblong or narrowly ovate, 

 pedicellate, about 30 x T[5 p. Sporidia 8, small, about 10 x 15 ju. 



On Acer Pennsylvanicum, A. spicatum, A. saccharinum, A, 

 dasycarpum, A. rubrum* 



Not rare throughout the country east of the Rocky Mountains, 

 though not reported in the extreme northwest. 



This is readily distinguished from U. Aceris, (DC.) by its simple 

 appendages and more numerous, very narrow asci. In some specimens 

 the mycelium is inconspicuous, but in specimens from Massachusetts 

 (Seymour) it is more abundant. The leaves affected by it can often 

 be distinguished at a distance, as the areas covered by it remain green 

 after the rest of the leaf has assumed its autumnal tint. 



U. Aceris, (DC.) 



Erysiphe Aceris, DC. Flore Franc. VI, p. 104. 

 Alphitomorpha bicornis, Wallr. Verhandl. I, p. 38. 

 Uncinula bicornis, Lev. Ann. Sci. Nat. XV, p. 153. 

 Uncinula Aceris, Sace. Syll. I, p. 8. 



Amphigenous. Mycelium variable, sometimes in conspicuous, 

 dense patches, sometimes spreading over one or both surfaces of the 

 entire leaf. Perithecia scattered, large, 150-200 //; appendages very 

 numerous, short, less than diameter of perithecium, once or more rarely 

 twice forked mostly beyond the middle, the elongated tips somewhat 

 tapering and strongly recurved or spirally wound. Asci 8-12, some- 

 what pear-shaped. Sporidia 8, about 14 x 30 p.. 



On maple leaves, California (Harkness). This exceedingly inter- 

 esting and characteristic species is inserted as American upon the 

 authority of Harkness and Moore (Pacific Coast Fungi, p. 32) where 

 it is named U. bicornis, Lev. 

 3 



