THE FUNGI WHICH CAUSE PLANT DISEASE 587 



the injured cuticle and causing rot. A ring of pink conidiophores 

 and conidia is formed around the margin of the scab. Inoculation 

 tests showed the fungus unable to penetrate through sound cuticle 

 though it readily made entrance through wounds. It has been 

 occasionally reported on living twigs and leaves and as a common 

 saprophyte has long been known. The first account of it in America 

 was from New York ^^ in 1902 though it was described in 1899 as 

 injuring pears in Germany. ^^^ 



Mycogone Link (p. 586) 



Hyphse intricately branched; conidiophores 

 short, lateral; conidia imequally 2-celled, the 

 upper larger, echinulate. 



There are about fifteen species of mycogenous 

 fungi which are probably conidial stages of Hy- 

 pomyces. See -p. 200. 



M. perniciosa Mag.^®^' ^^ 



White throughout, byssoid, deforming the 

 host; conidiophores short; conidia solitary, 

 more or less pyriform, almost colorless, 17- 



22 X 9-12 ;*. Pjq 393.— Mycogone, 



It is reported by Mrs. Patterson as the eomdiophores and 



'^ •' conidia. After Sac- 



cause of a mushroom disease m America, cardo. 

 A verticillium conidial stage was present but 

 no ascigerous form. 

 M. rosea Link, also occurs on mushrooms. 



Rhynchosporium Heinsen (p. 586) 



On leaf spots; hypha filiform, hyaline, creeping, septate; conid- 

 iophores erect, with incurved branches, hyaline, apically denticu- 

 late; conidia short-cjdindric, with a short oblique beak, medially 

 septate, hyaline. A monotypic genus. 



R. graminicola Hein. occurs on rye, wheat, and barley in Europe. 



Didymaria Corda (p. 586) 



Conidiophores simple, conidia borne apically, ovate, hyaline. 



About twenty species of leaf parasites. 



D. prunicola Cav. produces spots on plum leaves. 



