DEUTEROMYCETES (Fungi Imperfecti) 



As the name implies, these are secondary or propagative stages of other fungi, 

 principally Ascomycetes. In consequence, they do not constitute a natural class, 

 but form an artificial group kept together for convenience. Many of them are found 

 in association with the perfect form in nature, while the number of those linked 

 up by means of experimental cultures is steadily increasing. An enormous num- 

 ber of new genera have been described during the past quarter of a century, many 

 of them on trivial or very variable criteria. 



A natural system of secondary stages is obviously out of the question, short 

 of their assignment to the perfect forms. However, the grouping into orders 

 approximates this in some measure in view of the fact that pycnidium and stroma 

 often reflect the structure of the perfect form. Even among the Hyphomycetes 

 the resemblances probably indicate some community of relation to the perfect 

 forms, but the entire situation is complicated by the fact that some of the latter 

 possess two or more very dissimilar propagative stages, while essentially the same 

 type of secondary form may occur in widely separated orders of Ascomycetes. 



The Phomales are distinguished by the presence of the pycnidium, which 

 reflects the evolution of the perithecium and its final transition into the apothecium. 

 The Melanconiales represent a probable final condition of the latter in which the 

 protective cover has been suppressed, resulting in a simple stroma. The Hyphomy- 

 cetes or Moniliales are mycelial forms without differentiated pycnidia or stroma, 

 though the latter is sometimes so closely simulated in the Tuberculariaceae as to 

 warrant their inclusion in Melanconiales, as Hoehnel has done (1923:301). 



Order 20. PHOMALES 



Fruiting-body a pycnidium, the latter varying from globose to conic or elongate, 

 usually with a distinct ostiole, to dimidiate with a simple pore or astomous, or to 

 hysterioid, discoid or cupulate and opening by a cleft, lobes or circularly, single, 

 cespitose or with a subicle or stroma, the latter effuse, valsoid or dothideoid, im- 

 mersed, erumpent or superficial from the first, membranous to carbonous, waxy or 

 fleshy, typically dark but sometimes bright-colored; conidia borne on simple or 

 branched conidiophores or basidia, or the latter sometimes lacking and the conidia 

 then arising directly from the pycnidial wall, rarely endogenous; conidia various, 

 hyaline or dark, globose to filiform. 



Key to Families 



A. Pycnidia perithecium-like, typically globoid, ostio- 



late or astomous 



1. Pycnidia brown to black, membranous to car- 



bonous Phomaceae p. 176 



2. Pycnidia bright-colored, or hyaline, fleshj , 



sometimes gelatinous or waxy Zythiaceae p. 186 



B. Pycnidia dimidiate and usually more or less dis- 



tinctly radiate, rarely hysterioid Leptostromaceae p. 189 



C. Pycnidia apothecium-like or hysterioid, cupulate 



to discoid, opening circularly or less often by a 

 cleft or lobes, dark and subcarbonous to bright- 

 colored and fleshy Discellaceae p. 192 



175 



