422 Illinois State Laboratory of Natural History. 



decidua: Union, Oct. 25, 2014; Jersey, Oct. 13, 6287. Ulmus 

 Americana^ Jo Daviess, Sept. 19, 6003. Syringa vulgaris: 

 McHenry, Aug. 20, 13 73, 1214, Aug. 31, 1398; Cook, Sept. 8, 

 1464; La Salle, Sept. 12, 1500; Rock Island, Sept. 21, 1623; 

 McLean, Oct. 18, 1872, Aug. 18, 5632; Union, Nov. 1, 2185; 

 Jackson, Nov. 5, 2260; Jo Daviess, Sept. 20, 6039. Platanus 

 occidentalis : Champaign, Oct. 30, 6375; Union, Sept. & Oct. 

 (Earle). Juglans cinerea: Union, Sept. 22 (Earle). Juglans 

 nigra: Union, Oct. 22 (Earle). Gary a alba: Union (Earle). 

 Corylus Americana: McHenry, Aug. 20, 1169, Aug. 24, 1287; 

 Lee, Sept. 12, 5790; Stephenson, Sept. 14, 5879, Sept. 24,6066; 

 Jo Daviess, Sept. 16, 5941, Sept. 19, 6000; Ogle, Sept. 25, 6174. 



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 spores. 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) sub- 

 orbicular asci, while larger ones contain a greater number, 

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

 The spores are by no means constant in number, even in asci 

 from the same perithecium. It is manifestly impossible to 

 maintain specific distinctions based on such variable charac- 

 teristics; and it becomes necessary, as in other genera of the 

 family, to combine these rather widely varying forms. Aside 

 from the number of asci and spores, the forms included here 

 do not, however, present any very wide variations. In fact the 

 branching of the appendages, and the cellular structure of the 

 wall of the perithecium, are strikingly alike in all of them. 

 The specimens collected in Union county, on Juglans cinerea 

 and J. ?iigra, are sometimes very different from the type, 

 having appendages less than the diameter of the perithecium. 

 But on these same hosts other forms imperceptibly grade into 

 the characteristic ones, leaving no room for specific distinction. 



The form on Sijringa is usually known as M. Friesii, Lev. ; 

 that on Viburnum as M. viburni^ Howe; that on Sambiicus as 

 M. Van Bruntiana, Ger.; and that on Platanus as M. platani, 

 Howe. The others are usually referred to M. penicillafa, Lev. 



