412 Illinois State Laboratory of Natural History. 



Union, Sept. and Oct. (Earle). Quercus ruhra: Union, Nov. 1, 

 2196. Quercus (palustris?): La Salle, Sept. 17, 1582. Fagiis 

 ferrnginea: Union, Sept. 20 (Earle). Corylus Americana: 

 Lee, Sept. 12, 5794; Jo Daviess, Sept. 16, 5940; Ogle, Sept., 

 6192; Union, Sept. and Oct. (Earle). Betula nigra: Jersey, 

 Oct. 14, 6306; Union, Oct. 4, 6561. 



This frequently occurring species presents many variations 

 in the size of the perithecia, the length of the appendages, the 

 number and size of the asci, and the size of the spores; but 

 none of these forms seem constant enough to justify their 

 separation. On Liriodendron the mycelium is usually incon- 

 spicuous, the appendages but little longer than the diameter of 

 the perithecium, and the few^ (8-10) asci are large and broadly 

 ovate. On IJhnus the mycelium is abundant and persistent, 

 the perithecia and appendages medium, and the very numerous 

 (20-30) asci are small and narrow. On Quercus the perithecia 

 are very large, and the 10-15 asci and the spores are much 

 larger than on Ulmus. On Coruhis the perithecia are small, 

 but the appendages are very long. Asci and spores not 

 observed on this host. They seem to mature later than on the 

 others. 



This species has long been known as P. guttata, Lev., but 

 priority demands the use of the name given by Rebentisch, 

 (Sacc. Syl. Fung., L, p. 5). 



The peculiar yellow oil often occurring in the perithecia 

 of this family is here particularly abundant and noticeable. 

 In some cases, especially on Ulmus, the leaves affected by the 

 fungus turn yellow and fall prematurely. 



PODOSPH^RA, Kunze. 

 (Mycol., Hefte II., p. 111.) 



Perithecium containing a single ascus; appendages free from 

 the mycelium, dichotomously branched at the end. 



P. oxyacanthsB, (DC.) DBy. 



(Morph. und. Phys. der Pilze, III., p. 480.) 



Erysiphe oxyacanthx, DC. (Flore Franc, VI., p. 106). 

 Alphitomorpha tridactyla, clandestina, Wallr. (Flore Crypt. Germ., 

 III., p. 75S). 



