ABSTRACTPhysiological studies ofDichotomophthoropsis nymphaearumandSclerotium hydrophilumwere undertaken to determine the growth parameters for these two fungi. Optimum or near-optimum growth ofD. nymphaearumoccurred at temperatures of 25 and 30 C. Optimum temperature for growth of S.hydrophilumwas 30 C, although maximum sclerotial production occurred at 25 C. Both fungi were able to utilize all of the carbon sources tested.Dichotomophthoropsis nymphaearumgave lower mycelial yields on xylose, whileS. hydrophilumgrew poorly on maltose. Both fungi utilized inorganic and organic nitrogen sources, but mycelial yields were lower when ammonium sulphate served as the nitrogen source. Glycine was also a poor nitrogen source forS. hydrophilum.Thiamine was required by both isolates ofD. nymphaearumstudied and by one of the isolates ofS. hydrophilum.Light was not found to be essential for conidium production byD. nymphaearumor for the initiation of sclerotia byS. hydrophilum, although it did affect maturation of these structures. Pairing of six isolates of each fungus in all possible combinations and on several media failed to give evidence of a sexual response or production of a sexual state.