The reproductive phenology of certain species of Peyssonnelia inhabiting the infralittoral sciaphilic communities in relatively quiet environments has been analyzed. In general, the existence of two preferred periods of reproduction, autumn and spring, has been detected. In autumn the total percentage of fertile plants, as well as the reproductive intensity (/. e. the abundance of reproductive organs), is greater in the whole of the bathymetric profile studied. This behaviour is particularly evident in Peyssonnelia squamaria, P. rosa-marina f. saxicola, P. polymorpha and P. codana.These results suggest that the species of Peyssonnelia in the Mediterranean have a positive, although not absolute, response to short-day photoperiods (SD response).