The Classification of the Hyphomycetes

The classification of the Hyphomycetes is discussed with special reference to spore types conidiophore behaviour and initiation and development of spores. Eight basic morphological spore types are recognized : the blastospore, the gangliospore, the phialospore, the porospore, the arthrospore, the meristem-arthrospore, the spiculospore and the chlamydospore. No taxonomic significance is attached to the chlamydospore. It is pointed out that the forms now placed in the Mucedinaceae the Dematiaceae, the Tuberculariaceae and the Stilhaceae of Saccardo may be placed in six Families as suggested by the author earlier : (i) the Torulaceae (Type genus, Tonila Pers. ex Fries) for forms producing blastospores ; (ii) the Bactridiaceae (Type genus, Bactridium Kunze ex Fries) for those producing gangliospores ; (iii) the Tuberculariaceae (Type genus, Tubercularia Tode ex Fries) for those producing phialospores ; (iv) the Helminthosporiaceae (Type genus, Helminthosporium Link ex Fries) for those producing porospores ; (v) the Geotrichaceae (Type genus, Geotrichum Link ex Sacc.) for those producing arthrospores ; and (vi) the Coniosporiaceae (Type genus, Coniosporium Link ex Fries) for those producing meristem-arthrospores. The Families are subdivided into Sections on the basis of characters of the conidiophore related to spore initiation and development, the presence or absence and nature of "sporogenous cells", the presence or absence of "separating cells" and certain distinct modes of spore formation which are outlined. Twenty-four Sections are delimited and tentatively keyed out : thirteen in the Torulaceae, four in the Bactridiaceae, two each in the Tuberculariaceae the Helminthosporiaceae and the Geotrichaceae, and one in the Coniosporiaceae. A separate Section is provisionally suggested for forms producing spiculospores. Typical examples of genera for each Section are given together with illustrations. Some of the difficulties still requiring solution are mentioned, including those relating to speculations about the classification of the Hyphomycetes vis-a-vis their perfect stages so far as known. It is emphasized that critical and thorough studies on generic types inadequately or imperfectly understood are an urgent necessity.