Hymenocladiopsis crustigena (Rhodymeniaceae), a new genus and species of marine Rhodophyceae from the Antarctic Peninsula

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Abstract
A new genus and species of marine Rhodophyceae, Hymenocladiopsis crustigena, is described from the Antarctic Peninsula and assigned to the Rhodymeniaceae. Thalli consist of large, pinnately branched blades borne on an extensive crust. The cortex of the blade is composed of one or two layers of cells. The medulla, in which intercellular spaces or cavities are present, is composed of large and small cells, some of which bear spherical gland cells. Reproductive structures are produced on the main blade or on pinnae. The carpogonial branch is a cluster of three cells that fuse following fertilization. Cystocarps, which lack a tela arachnoidea, are large and protuberant. Tetrasporangia are tetrahedrally divided. Hymenocladiopsis crustigena occurs subtidally along the Antarctic Peninsula from Marguerite Bay to the South Orkney Is. It differes from Hymenocladia by having tetrasporangia that are terminal rather than intercalary and gland cells that are medullary rather than cortical. It appears to be related to a little known plant from South Georgia ascribed erroneously by Reinsch to Gracilaria as G. prolifera.