ADVANCES IN THE STUDY OF SO-CALLED AQUATIC HYPHOMYCETES

Progress in the study of the freshwater aquatic fungal flora (mainly hyphomycetes) of submerged decaying leaves of dicotyledonous trees and shrubs, since the discovery of the flora in 1942, is reviewed. The abundant occurrence of liberated conidia, which tend to be of distinctive form, in persistent foam on a stream is noted and illustrated by an example from Scotland. Developments in the taxonomy of these fungi since 1942 are noted. About 60 genera and around 120 species are now recorded. In a number the perfect stage has been discovered. In most cases it has proved to be an ascomycete, but it is sometimes a basidiomycete. Conidium development in aquatic hyphomycetes is discussed in the light of recent views on the classification of conidial types. It is argued that the most valid distinction is between phialoconidia and other types, rather than between those of blastic and those of thallic development. Dispersal is discussed with special reference to upstream spread and the problem of dispersal from one isolated water system to another. Finally, attention is given to the ecology and general physiology of these fungi. Their possible importance in processing decaying leaves for subsequent consumption by small aquatic animals is considered. The terrestrial occurrence of many “aquatic hyphomycetes” is noted and it is suggested that “amphibious hyphomycetes” might be a better term.