SUMMARYFuligo septicaspores in mass suspensions germinate with logarithmic kinetics, indicating that spore germination is a complex, controlled phenomenon and not random. Spores germinate at higher rates in filtrates of spore suspensions than in phosphate buffer. The amount of stimulation of germination is related to the degree of dilution of the filtrates and the age of the spores from which the filtrates are prepared. Evidence indicates that spore germination is influenced by a soluble, dialyzable, auto-catalytic factor associated with the spores that is present in the aethalium prior to the moistening of the spores.