Parasitic Fungi of Illinois. 413 



Erysibe tridactyla, Rabh. (Deutschl. Krypt. Fl., I., p. 273). 



Erysibe clandeslina, Lk. (Spec. Plant., VI., I., p. 103). 



Podosphssra Kunzei, clandeslina, L^v. (Ann. Sci. Nat., Ser. III., 



Tome XV). 



Podosphssra trydactyla, myriillina, DBy. (1. c. III., p. 48). 



Podosphsera myrtillina, Kunze (Mycol., Hefte II., p. 111). 



Podosphiera minor, Howe (Torr. Bull., V., p. 3). 



Amphigenous. Mycelium variable, often abundant, per- 

 sistent, perithecia 65-110 ^. dark, opaque, reticulations regu- 

 lar, about 10-15 ft, evident when young, scarcely observable 

 when old, except by the uneven surface; appendages 8-20, 

 dark brown for more than half their length, frequently septate, 

 1-4 times as long as the diameter of the perithecium, 3-5 

 times dichotomously forked, branches short, often swollen, tips 

 recurved; ascus broadly elliptic or orbicular, about 50 by 60 /*, 

 thick walled; spores usually 8. 



On Cratcegus tomentosa var. pyrifolia: Union, Nov. 3, 

 2194; A'dams,, July 3, 5394. Cratcegus sps.- Union, Sept. 

 (Earle). Prunus Anericana: Lee, Sept. 9, 5744. Prunus 

 cerasMS (cultivated): McHenry, Aug. 24, 1289; Rock Island, 

 Sept. 21, 1625; Piatt, Aug. 16, 1151; Adams, June 29, 5342; 

 Union, Aug. 22 (Earle). 



European botanists agree in dividing what is here included 

 under P. oxyacanthce, into three species, as follows: — 



P. oxyacanthce, (DC.) DBy. Appendages 8 or more, about 

 equal to the diameter of the perithecium, standing erect on its 

 upper surface. On Cratcegus, Sorbus, and Mespilus. 



P. tridactyla, (Wallr. ) DBy. Appendages 3-7, standing 

 erect in a parallel bundle on the summit of the perithecium. On 

 Prunus sps. 



P. myrtillina, (Schubert) Kunze. Appendages 6-10, aris- 

 ing from the upper surface of the perithecium, but radiating 

 divergently or reflexed. On Vaccimum. 



European specimens on the above hosts show these distin- 

 guishing characters sufBciently well. American specimens on 

 Prunus often have as many as twenty appendages, and though 

 they all stand on the upper half of the perithecium it is only in 

 rare cases that they are collected in an erect cluster at the summit, 

 as in P. tridactyla. They usually radiate even more divergently 

 than in P. myrtillina. In American specimens on Cratcegus 



