22 



In Europe three species are described as follows; 



P. OxyacanthcB, (DC.) DBy. — Appendages 8 or more, about equal 

 to the diameter of the perithecium, standing erect on its upper surface. 

 On Gratcegus, Sorbus and Mespilus. 



P. tridactyla, (Wallr.) DBy.— Appendages 3-7, standing ei-ect in 

 a parallel bundle on the summit of the perithecium. On Prunus sps. 



P. myrtiJlina, (Schubert) Kunze. — Appendages 6-10, arising 

 from the upper surface of the perithecium, but radiating divergently- 

 or reflexed. On Vaccinium. 



European specimens on the above hosts show these distinguishing 

 characters sufficiently well, but American specimens on Prunus can- 

 not be separated from those on Crataegus, etc. There appear to be 

 none on Vaccinium. Whatever may be done with Eui;opean forms, 

 the American ones must be considered one species. 



P. biuncinata, C. & P. Erysiphei of the U. S. Journ. Bot. 1872. 

 Pk. 25th Rep. p. 94. 



Amphigenous. Mycelium thin, arachnoid, rather persistent. 

 Perithecia small, 70-90 n, scattered; appendages 6-12, 3-5 times as 

 long as the diameter of the perithecium, hyaline, with a conspicuous, 

 widely spreading fork at the apex, each branch of which is sometimes 

 divided. Ascus globose. Sporidia mostly 18-21 [x long. 



On Hamamdis Virginiana, Massachusetts (Seymour), New York 

 (Peck), Illinois (Waite). 



An easily recognized species, by the unique character of the tips 

 of the appendages, which approach, thougli they are easily different 

 from those of Uncinula Aceris. The mycelium shows much more on 

 the upper surface of the leaves, but is also common below. 



MICROSPHJIRA, L^v. 



Ann. Sci. Nat. Ser. in, Tome XV, p. 381. 



Perithecium containing several asci. Appendages free from the 

 mycelium, more or less dichotomously branched at the end. 



M. Menispermi, Howe, Bull. Torr. Bot. Club, V, p. 3. 



Epi]ihyllous. Mycelium rather abundant, thin and widely effused, 

 but thickened in certain circular spots, of which there are usually not 

 more than three or four on a leaf Perithecia aggregated upon the 

 special denser spots of the mycelium, otherwise remotely scattered, 

 black, very variable in size, 60-115 // diam; appendages not numer- 

 ous, 8-15, rather rigid, tinted at base, exceedingly variable in length 

 and amount of branching, 1-7 times diameter of perithecium in length 

 and 1-7 times dichotomously branched, the branches of the first 



