Abstract
A method was developed for the quantitative estimation of propagules of saprolegniaceous fungi present in freshwater. Both laboratory and field work suggested that estimations were concerned with zoospores rather than gemmae, oogonia, or mycelial fragments. All estimations were made from surface water only. At Windermere lake margin total Saprolegniales estimation figures ranged from <25 to 5200/liter. At Windermere lake center total Saprolegniales estimation figures were never more than 100/liter and a mean figure of 11/titer was derived for this situation.