27 



31. Aliii, (DC.) 



Erysiphe Alni, Bctultf, DC. Flore Franc. VI. p. 104, 



Alphitomorpha penicillata, Wallr. Verhandl. Naturf. Freunde 1, p. 40. 



Eiysibe penicillaia, Lk. Spec. Plant. VI. I. p. 113. 



Erysiphe I'iburni, Duby, Bot. Gall. II. p. 872. 



Erysiphe Ceanothi, Vibnrni^ SytlngtE, Schw. N. A. Fungi, pp. 269, 270. 



MicrosphfEra Hedzuigii, penicilhita, Friesii, Lev. Ann. Sci. Nat. Ser. Ill, Tome XV- 



Microsphcera Platani, Howe, Torr. Bull. V, p. 4. 



Microsphczra Vibiirni, Howe, Torr. Bull. V, p. 43. 



Microsph&ra pulchra, C. & P. Erysiphei of U. S. in Journ. of Bot. 1872. 



MicrosplicEi a Xtmopanthis, Peck, 3Sth Rep. X. Y. State Mus. p. 102. 



Microsph&ra Alni, Winter, Die Pilze II. p. 38. 



AmpMgenous. Mycelium often delicate and evanescent, some- 

 times abundant and persistent. Perithecia usually small. 75-100 IJL, 

 sometimes larger, 100-130 //., wall tissue compact, rather fragile, re- 

 ticulations not large, 10-15 //; appendages 6 or 8 to 15 or 20, hyaline, 

 usually tinted at base, often somewhat roughened, usually about equal- 







ino-, but varying from less than, to more than twice the diameter of the 



O t 



perithecium. 4-6 times dichotomous, branches varying in length and 

 angle of divergence, but always regular and symmetrical, tips acute 

 distinctlv. oltcn strongly recurved. Asci varying with the size of the 



/ / , / 



perithecium from 2 or 3 to 8 or more, usually 4 or 5, ovate when 

 numerous, suborbicular when lew. Sporidia 4-8. variable, mostly 

 small, averagiiig about 20 /i long. 



On Ilex decidmi:, Nemopanthes fascicvlaris, Euonymus atro- 

 u*, Celastrus scanrfrttN, Ceanothus Americanus^ Syringa 

 x. Cornns stolon tfewt, (7. wrircd. C. alternifoUa, Viburnum 

 acerifolium, V. pubescens, V. dentatum, V. lentago, V. prunifolium 

 Lonicera sempervirens, L. Sullivantii, L. kirsuta, L. glauea, An- 

 <1 1'otncdii liyiixtrhin. Rhododendron nudiflorum, Foi'cxticni acumi- 

 iKitn. Ulnmx Americana, Phttnnu* occidentalism Juglans cinerea, 

 J> iiifjra. Carya alia. Bctula lent ft. B. lutea. B. pumila, Alnus 

 inciina, A. set'/'iilcttf, Corylus Americana, C. ro^i fata, Ostrya Vir- 

 yhiica, Carpinus Caroliniana, Cvxtunea xativa var. Americana, 



Fagus ferruginea. 



The forms here included under M. Alni have been assigned by 

 different authors to various species, distinguished, for the most part, by 

 the number of the asci and sporiclia. In all of these forms, the size of 

 the perithecia, even when standing side by side on the same leaf, is 

 quite variable, and, as a consequence, the number and shape of the asci 

 they contain vary equally widely. Very small perithecia contain only 

 a few (2-4) suborbicular asci, while larger ones contain a greater num- 

 ber, which, owing to lateral crowding, are narrower and longer. The 

 sporidia are by no means constant in number, even in asci from the 

 same perithecium. It is manifestly impossible to maintain specific dis- 



