AbstractThe effect of mercuric chloride on akinete germination and sporulation with respect to time lapse and extent was studied inPithophora oedogonia(Mont.) Wittrock (Cladophorales, Chlorophyceae). At HgCl2concentrations from 1.25 to 45 mg/l akinetes showed progressive delay in the initiation and reduction in the extent of germination. HgCl2concentrations of 60 mg/l and above proved to be completely lethal to the spores as they failed to germinate. The time necessary for the initiation of akinete formation and the percentage sporulation also decreased with an increase in the concentration of HgCl2from 1.25 to 45 mg/l where spore germination was encountered. Inactivation of enzymes and metabolic inhibition seemed to be the cause of spore lethality.