THE FUNGI WHICH CAUSE PLANT DISEASE 555 



Melanconiacese-Hyalodidymse (p. 537) 

 Conidia hyaline, 1-septate, ovoid to fusoid. 



Key to Gexeba of Melanconiaces-Hyalodidymse 



Conidia mutic 



Saprophjrtic, on stems and fruits 1. Septomyza. 



Biogenous, typically on leaves 2. Marssonia, p. 555. 



Conidia 3 to 4-ciliate at each end 3. GlGesporiella. 



Marssonia Fisch 



Acervuli globose-discoid, pale, conidia ovate to elongate. In 

 part =Gnomonia, Trochila, Pseudopesiza. 



Some seventy-five species, all leaf parasites, several of eco- 

 nomic importance. 



M. castagnei (D. & M.) Sacc. on Popiilus = Trochila popularum. 

 See p. 157. 



M. juglandis (Lib.) Sacc. on walnut =Gnomonia 

 leptostyla. See p. 275. 



M. populi (Lib.) Sacc. 



Spots suborbicular, epiphyllous, separate or con- . 



fluent, brown, darker margined, acervuli convex ^^^ 373 _m per- 

 to applanate, fulvous; conidia obovate to subpyri- forans, conidio- 

 form, 20 x 12 n, constricted at the septum, l^^^^ Aftet 

 straight or cvirved. . Selby. 



It is common on leaves of Populus as the cause of blighting 

 of lateral twigs. It is injurious in nurseries.^ 



M. panattoniana (Berl.) Mag. is found on lettuce in Italy; 



M. secalis (Oud.) Mag. on rye; 



M. martini S. & E. on oak; 



M. potentillae (Desm.) Fisch as the cause of a disease of the 

 strawberry in Europe. 



M. rosae Trail causes premature fall of rose leaves. 



M. perforans, E. & E.i^s 



Spots small; irregular, 1-2 nun., pale, soon deciduous; acervuli 



