124 THE FUNGI WHICH CAUSE PLANT DISEASE 



Ascoma opening tardily, enclosed by 

 a tough covering which becomes 

 torn open at the maturity of the 

 spores 

 Ascoma roundish, opening by stel- 

 late or radiating fissures 4. Phacidiales, p. 154. 



Ascoma elongate, opening by a 



longitudinal fissure 5. Hysteriales, p. 159. 



Ascoma at maturity closed and tuber- 

 like, subterranean, 6. Tuberales. 



Asci collected in a cylindric or globose 



perithecium 



Perithecia sessile, solitary and free, or 



united and embedded in a stroma 



Asci arranged at different levels in 



the perithecium 7. Aspergillales, p. 164. 



Asci arising from a common level 



Mycelium superficial, perithecia 



scattered, globose and without 



apparent ostiole, or flattened 



and ostiolate 8. Perisporiales, p. 170. 



Mycelium nearly superficial, peri- 

 thecia ostiolate 

 Perithecia and stroma (if pres- 

 ent) fleshy or membranous, 



bright colored 9. Hypocreales, p. 195. 



Perithecia and stroma (if pres- 

 ent) hardened, rarely mem- 

 branous, dark colored 

 Wall of perithecia scarcely 

 distinguishable from the 



stroma 10. Dothidiales, p. 215. 



Perithecia with distinct wall, 

 free or embedded in the 



stroma 11. Sphsriales, p. 221. 



Perithecium borne on a short pedicel; 

 microscopic fungi parasitic on 

 insects 12. Laboulbeniales. 



Of these all contain plant parasites with two exceptions; the 

 Tuberales, which bear underground tuber-like ascocarps, some of 



