Hydrolithon farinosum (Lamouroux) comb. nov.: implications for generic concepts in the Mastophoroideae (Corallinaceae, Rhodophyta)

Abstract

Studies of the type of Fosliella (Corallinaceae, Rhodophyta), F. farinosa (Lamouroux) Howe, have shown that it possesses features considered characteristic of Hydrolithon. Tetrasporangial conceptacle pore canals are lined by conspicuous elongate cells arising from filaments interspersed amongst sporangial initials; these cells do not protrude laterally into the canal and are oriented more or less perpendicularly to the roof surface. This new information has led to the conclusion that Fosliella and Hydrolithon are congeneric. Thus, Fosliella Howe 1920 becomes a heterotypic synonym of Hydrolithon Foslie 1909 and Fosliella farinosa (Lamouroux) Howe is transferred to Hydrolithon as H. farinosum (Lamouroux) comb. nov. It has also been shown that the spore germination disc consists of a 4-celled central element surrounded by 12 cells, and it is proposed that thin plants traditionally attributed to Fosliella be referred to as the Fosliella-state of Hydrolithon. Recent changes to generic delimitation within the subfamily Mastophoroideae are also summarized in a key to genera.