58 
IMycologia 
It seems desirable to retain this form-genus, since some of the 
forms have not yet been definitely associated with known species 
of the various genera of the Erysiphaceae. 
Culture work on species of this genus is in progress, and, there- 
fore, a mere enumeration of the species examined is given at 
present. 
1. Acrosporium hyalina (Fr.). 
Monilia hyalina Fr. Ohs. Mycol. i : 210. 1815. 
Acrosporium monilioides Nees, 1 . c. 
On various grasses. The conidial stage of Erysiphe graminis DC. 
2. Acrosporium obductum (Ellis & Lang.). 
Oidium obductum Ellis & Lang. Jour. Mycol. 6: 35. 1890. 
On living leaves of young Quercus. 
3. Acrosporium Tuckeri (Berk. & Br.). 
Oidium Tuckeri B. & Br. Grev. 7: 28. 1878. 
On vine leaves. Probably the conidial stage of Uncinula neca- 
tor (Schw.) Burrill. 
4. Acrosporium leucoconium (Desm.). 
Oidium leucoconium Desm. Ann. de Sci. 13 : 102. 1829. 
The conidial stage of Sphaerotheca pannosa (Wallr.) Lev. 
There is a variation in the spelling of the specific name. The 
following spellings occur, leuconium and leucogonium. 
6. Acrosporium compactum (Cooke & Ellis). 
Oidium compactum Cke. & Ell. Grevillea 7: 39. 1878. 
On Quercus alba. 
7. Acrosporium Euonymi-japonici (Salmon). 
Oidium Euonymi-japonici Salmon, Ann. Mycol. 3 : 6. 1905. 
No specimen of this species was seen but it is said to be near 
A. leucoconium. 
8. Acrosporium pirinum (Ellis & Ev.). 
Oidium pirinum Ellis & Ev. Jour. Mycol. 5: 68. 1889. 
On leaves of Pirns coronaria. 
9. Acrosporium sp. 
? Microsphaera Platani Howe, Bull. Torrey Club 5: 4. 1874. 
