AbstractAttention is drawn to reports of gemmae inPleuroclada albescensandP. islandica, and to the evidence from which Krzakowa (1972) deduces thatP. islandicashould be restored to specific status. A study of British and non-British material reveals that the criteria for distinguishing two species are untenable, and supports the view that var.islandicais merely a habitat form ofP. albescens. The development of gemmae inPleuracladais discussed since their origin was inaccurately described by Krzakowa.