THE FUNGI WHICH CAUSE PLANT DISEASE 251 



Key to Genera of Pleosporacese 

 Spores 1-celled 

 Spores with blackish appendages, elon- 

 gate, hyaline 1. Urospora. 



Spores unappendaged 

 Spores elongate, hyaline or hght yel- 

 low 2. Physalospora, p. 262. 



Spores elongate, fusoid, hyaUne; tips 



bent 3. Theixya. 



Spores 2-celled 

 Spores with the 2 cells very unequal in 

 size 

 Upper cell ihe smaller; parasitic on 



Riccia 4. Arcangelia. 



Basal cell the smaller; saprophytes. ... 5. Apiospora. 

 Spores with both cells about equal 

 Perithecia hairy; spores hyaline or 



brown 6. Venturia, p. 253. 



Perithecia smooth 



Spores hyaline 7. Didymella, p. 255. 



Spores brown 



Perithecia not stromatic 8. Didyinosph3eria,p.256. 



Perithecia borne on a stroma 9. Gibbellina, p. 256. 



Spores more than 2-celled 

 Spores elongate, with cross walls only 

 Spores appendaged 

 Spores clavate, 4 to 6-celled, brown, 

 the basal cell hyaline long- 



appendaged 10. Rabentischia. 



Spores filiform, many-celled, with 



filiform appendages 11. Dilophia, p. 257. 



Spores not appendaged 

 Spores fusoid or elongate, blunt, never 

 filiform or separating into cells 

 Spores elongate, 3 to many-celled, 

 hyaUne or brown 

 Spores with a thick, dark-brown 

 epispore and a thin hya- 

 line endosporc, 4-celled, el- 

 lipsoid 12. Chitonospora. 



