27 



M. Alni, (DC.) 



Erysiphe Alni, Betula, DC. :?lore Prailc. Vl, p. ro4. 



Alphitomovpha penicillata, Wallr. Verhandl. Naturf. Freunde 1, p. 45. 



Erysibe penicillala, Lk. Spec. Plant. VI, I, p. 113. 



Erysiphe Viburm, Duby, Bot. Gall. II, p. 872. 



Erysiphe Ceanoiki, Viburni, Syiingtz, Schw. N. A. Fungi, pp. 269, 270. 



Microsphmra Hedwigii,pe7ncillata, Friesii, Lev. Ann. Sci. Nat. Ser. Ill, Tome XV- 



Microsphesra Plaiani, Ho.we, Torr. Bull. V, p. 4. 



MicrospkeEra Viburrd, Howe, Torr. Bull. V, p. 43. 



Microsphcera pulchra, C. & P. ^rysiphei of U. S. in Journ. of Bot. 1*872. 



MicrosphtEra Neniopanthis, Peck, sSth Rep. N. Y. State Mus. p. 102. 



Microspkcera Alni, Winter, Die Pilze II. p. 38. 



Amphigenous. Mycelium often delicate and evsmescent, some- 

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

 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- 

 ing, but varying fi-om less than, to more than twice the diameter of the 

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

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

 distinctly, often 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 few. Sporidia 4-8, variable, mostly 

 small, averaging about 20 n long. 



On Ilex decidua, JSfemopanthes fascicularis, Euonymus atro- 

 purpureus, Celastrus scandens, (Jeanothus Amsricanus, Syringa 

 vulgaris, Cornus stolonifera, C. sericea, C. alternifolia, Viburnum 

 acerifolium, V. pubescens, V. dentatum^ V. lentago, F". prunifolium, 

 Lonicera sempervirens, L. Sullivantii, L. hirsuta, L. glauca, An- 

 dromeda ligustrina, Rhododendron nudiflorum, Forestiera acumi- 

 nata, Ulmus Americana, Platanus occidentalis, Juglans cinerea, 

 J. nigra, Cary<x alba, Betula lenta, B. lutea, B. pumila, Alnus 

 incana, A. serrulata, Corylus Americana, C. rostrata, Ostrya Vir- 

 ginica, Carpinus Caroliniana, Castanea sativa var. Amer-icana^ 

 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 sporidia. 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 Irom the 

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



