Morphological and taxonomic relationships among branched, ligulate members of the genus Desmarestia (Phaeophyceae, Desmarestiales), with particular reference to South African D. firma

Abstract

An examination is made of the reproductive anatomy and the morphology of branched, ligulate members of the genus Desmarestia from worldwide localities. Entities from southern Africa, New Zealand, South America, Gough Island, northwestern America, and Europe show varying degrees of morphological overlap, but all possess sporangia similar in size and shape to, and scattered among, the vegetative cortical cells. Specimens from Signy Island (South Orkneys) have sporangia subtended by stalk cells, interspersed with sterile paraphyses, and arranged in a palisadelike sorus (Antarctic type). The taxonomic implications of these findings are discussed. The New Zealand and Gough entities are referred to D. ligulata (Stackhouse) Lamouroux and the name D. firma (C.Ag.) Skottsb. is retained for the southern African entity.