THE FUNGI WHICH CAUSE PLANT DISEASE 285 



Key to Genera of Xylariaceas 



Stroma encrusted, shield-form, globose or 



hemispheric, without a sterile base. ... I. Hypoxylea. 

 Conidial layer beneath the surface of the 



stroma, erumpent l. Nummularia, p. 285. 



Conidial layer free from the first 

 Stroma encrusted 



Spores 1-celled 2. Bolinia. 



Spores 2-celled 3. Camarops. 



Stroma discoid to hemispheric,' en- 

 crusted together 

 Young stroma fleshy, covered by 



conidia, at length carbonous ... 4. TTstulina, p. 286. 

 Stroma carbonous or woody from the 

 first 

 Stroma without concentric layers. 5. Hjrpoxylon. 

 Stroma with concentric layers .... 6. Daldinia. 

 Stroma erect, simple or branched, clavate or 



cylindric, with a sterile base II. Xylaries. 



Most of these genera are saprophytic on wood or bark. 



Nummularia Tulasne 



Stroma orbicular, cupulate or discoid, becoming black, mar- 

 ginate; perithecia monostichous, peripheral, immersed; asci cy- 

 lindric; spores subelliptic, continuous, dark. 



The genus contains forty species. Only one is recorded as 

 injurious. 



N. discreta (Schw.) Tul. 



Stroma erumpent, orbicular, 2-4 mm., cupulate, with a thick 

 raised margin; ovate, cylindric, nearly 1 mm. long, abruptly con- 

 tracted above into a short neck; asci llQ-120 x 10-12 fi; spores 

 subglobose, nearly hyaline, then opaque, 10-12 >i; paraphyses 

 filiform. 



This fungus is usually a saprophyte but has been reported by 

 Hasselbring as a serious parasite on the apple in Illinois.^ 



The myceliimi grows more rapidly in the wood than in the bark, 



