The morphology and relationships of Husseyella rubra (Harvey) comb. nov. (Rhodomelaceae, Rhodophyta)

Abstract

The monotypic genus Husseyella Papenfuss [type species, H. australis (J. Ag.) Papenfuss (=H. rubra (Harvey) comb. nov.)] is distinguished from other genera in the tribe Chondrieae (Rhodomelaceae) by the production of reproductive structures (male unknown) in short branchlets (2–3 mm long) which occur in clusters of up to 10 in the axils of the branches. The procarps appear to be formed subterminally on these short branchlets, and subsequently there may develop 1 or 2 cystocarps per branchlet. Tetrasporangia occur in the cortex of the branchlets. Ruthenium red-positive cell wall thickenings which occur in pericentral cells and subcortical cells in some parts of the thallus are distinctive in form, becoming lobed and very thick in older cells, almost filling the lumen of the cell. The combination of features which are distinctive at the specific level include the tendency towards subpolychotomous branching, the characteristic cross section of median branches showing regular rings of pericentral and subcortical cells separated by rhizoidal growth, and the formation of a secondary cortex in lower parts of older plants. Our knowledge of H. rubra depends on about 13 collections, the most recent of which was in 1954.