THE FUNGI WHICH CAUSE PLANT DISEASE 195 



from all sooty molds. Among these are the genera Aschersonia '" 

 and Sphserostilbe. 



Microthyriaceae (p. 170) 



Mycelium superficial, dark; perithecia superficial, separate, 

 shield-shaped, unappendaged, black, membranous to carbonous, 

 formed of radiating chains of cells; asci 4 to 8-spored, short; pa- 

 raphyses usually present. 



A family of over twenty genera and more than three hundred 

 species, chiefly poorly understood. 



Only two species have been noted as serious economic patho- 

 gens; Scolecopeltis seruginea Zimm. and Microthyrium coffae 

 both on coffee in Africa. 



The genera of the Ascomycetes which remain to be treated, 

 and which are separated from those preceding by the possession 

 of an ostiole, are by some known under the name Pyrenomycetes. 

 Cf. p. 170. There are three orders, the Hypocreales, Dothidiales 

 and Sphseriales. 



Hypocreales (p. 124) 



The chief character separating this order from other Pyrenomy- 

 cetes is the brighter color — ^yellow, purple, scarlet, red, etc. — and 

 the more tender texture of its perithecia, — soft, fleshy, cottony, 

 patellate or effused. 



The perithecium also differs from that of the preceding orders in 

 the possession of a distinct opening, ostiole, for the exit of spores. 



Perithecia globose to cylindric or flask-shaped, free on the sub- 

 stratum (rarely subepidermal) or united by a common matrix, 

 which varies from a cottony subiculum to a distinct fleshy stroma, 

 wall membranous or at least not truly carbonous; asci cylindric, 

 clavate or subovoid, mostly 4 to 8-spored but often becoming 

 16-spored by the separation of each original spore into two globose 

 or subglobose cells; spores simple or compound, hyaline or colored, 

 globose to filiform. 



Conidia are usually produced freely, each genus usually possess- 

 ing at least one form of free-borne conidia, while in some genera 

 several different kinds of conidia are found. Pycnidia are rare. 

 Often the ascigerous stage is nearly suppressed and rare while 

 one or more of the conidial forms predominates. 



