Aquatic hyphomycetes are fungi that most commonly occur on dead leaves in streams and rivers and sporulate under water. They are also known as freshwater hyphomycetes (Nilsson 1964), amphibious hyphomycetes (Michaelides and Kendrick 1978), or Ingoldian fungi (Webster and Descals 1981). A majority form tetraradiate conidia (essentially with four diverging arms), some produce sigmoid conidia (long, wormlike, generally curved in more than one plane). Some have spores of more conventional shape.