180 IOWA ACADEMY OF SCIENCES. 



Spiraea, but there is no mention of its occurrence on Pyrus. 



Hitchcock* records the occurrence of Podosphaera tridactyla 

 upon Crataegus tomentosa, C. imnctata and seedling cherries, 

 but he does not mention the apple. 



Weberf reports Podosphaera tridactyla on cultivated cherry 

 and wild plum, but nowhere is any mention made of Sphaero- 

 theca mall or any other mildew upon the apple. 



In the Perisporaceae of the Kellerman & WernerJ list in the 

 catalogue of Ohio plants, Podosphaera oxyacanthia is reported 

 on Spyraea and Prunus cerasus, but there is no mention of the 

 occurrence of powdery mildew on the apple. 



Ellis and Gerard, § who worked up the fungi in catalogue of 

 plants of New Jersey, do not report the apple as affected. 



Burrillll correctly refers the apple powdery mildew to S. 

 mall (Duby), Burrill. 



Duby^ wrote a very short description of this species under 

 Erysiphe mali. Burrill who examined the E. mali Duby, in 

 Roumeger's fungi Gallici exsiccati, says it appears to be a 

 Sphaeratheca and the same as the American material. There 

 is also another E. mali, Moug' which is considered to be by 

 these authors a form of Alphitomorpha adunca. There can be 

 little doubt that our fungus is identical with that described by 

 Duby, and that the European Sphaerotheca castagnei f. mali, 

 sometimes referred to this species, is identical with the 

 American form. The ^S'. leucotricha E. and E.,^ has also been 

 referred to the species. 



The writer, in 1893, called attention to the common occur- 

 rence of this fungus in lowa^ under the name of Sphaerotheca 

 mali, following the Burrill nomenclature. 



Fink* called attention to its occurrence in the vicinity of 

 Fayette, in 1894. The writer distributed this fungus from 

 Iowa' in 1893?, and A. J. Grant,' from Newfane, Vt , in 1895. 

 Quite recently Grant' has figured and described the fungus. 



♦Bull. la. Agr. Coll. Bot. Dept. 1886: 64. 



t Cat. Fl. Nebr. 50. 



*Geologyof Ohio, 7: 330. 



§ New Jersey Geological Survey 2: SOT. 



II In Ellis and Everbart, N. A. Pyrenomycetes 6. 



TBot. Gallicum 1: 869. 



IWallroth Fl. Oyrpt. Germ. 4: 755. 



2 Jour. Myc. 4: 58 Burrill. In Ellis and Everbart N. Am. Pyreu. 6. 



3 Bull. la. Agrl. Exp. Sta. 28: 921. Proc. la. Acad, of Sol. 1*: 92. 1893. 



4 Proc. la. Acad, of Scl. 1* 103. BUgbts, Orchids and Ferns 7: 1894. 



5 Ellis and Everbart N. Am. Fung. No. 3213. 



6 Fung. Oolunb. No. 986. 



7 Bull. Torrey Bot. Club. 26: 373. pi. 36i. 



