530 THE FUNGI WHICH CAUSE PLANT DISEASE 



An undetermined species has been reported as a "fly speck" on 

 cabbage."* 



Piggotia Berkley & Brown (p. 528) 



Pycnidia applanate, inequilateral, thin-membranous, later with 

 a stellate cap which is thrown off forcibly; conidia elongate or 

 cylindric. 



A genus of less than ten species. 



P. astroidea Berk. & Br. parasitizes elm leaves. 



P. fraxini B. & C. 



Perithecia hypophyllous; spores oblong, 5-7 n long. On ash, 

 causing leaf spot. 



Leptostroma Fries (p. 529) 



Pycnidia dimidiate, subsuperficial, applanate, elongate, black, 

 more or less hysterioid; conidia ovate, elongate or allantoid. 

 In part=Hysteriaceae. There are some sixty species. 

 L. larcinum Fcl. on larch=Mycosphserella larcina. See p. 249. 

 L. piricola B. & S. occurs on the pear; 

 L. punctifonne Wallr. on willow. 



Labrella Fries (p. 529) 



Pyciudia black, round, often indefinite; spores long, fusiform, 

 or spherical, hyaline, continuous. 

 L. piricola Bres. & Sacc. is on pear leaves; 

 L. coryli (Desm. & Rob.) Sacc. on Corylus. 



Melasmia L6viell6 (p. 429) 



Pyraiidia dimidiate, carbonous, black, often on an effused black 

 stroma; conidia allantoid. 



In part=Rhytisma. Over twenty species. 



M. acerina L6v. is the conidial form of Rhytisma acerinum. 

 See p. 158. M. punctata S. & R. and M. salicina L6v. of the two 

 corresponding Rhytismas. See p. 158. 



