Biological Species in Pleurotus
RONALD H. PETERSEN, KAREN W. HUGHES, AND NADEZHDA PSURTSEVA
Diagnostic Characters
Many visible characters have been used to circumscribe the genus, but few have proven worthwhile. The pleurotoid basidiome does not extend to centrally-stipitate basidiomata such as those of P. dryinus or P. levis. White spores in mass does not include P. pulmonarius or P. cornucopiae, spores of which usually bear a distinct violaceous tint. The genus includes species with both monomitic or dimitic tramal tissues (especially stipe). Decurrent lamellae are doubtful in P. calyptratus. A partial veil is present in the P. dryinus complex as well as in P. calyptratus.
A single unique generic character emerges: production in culture (and occasional cheilo- pilei- or pleurocystidia) of nematostatic microdroplets born on simple, short, aculeate (not on gloeosphex, hour-glass-shaped) branches. Miller (1984) first suggested that such microdroplets were a hallmark of Pleurotus, and Petersen (1993) reinforced this idea.