Studies on pleonosporium and mesothamnion (Ceramiaceae, rhodophyta) with a description of a new species from natal

Abstract

Ontogenetic studies of procarps of Mesothamnion caribaeum Boergesen, the type species of the genus, show that it does not differ in procarp structure from Pleonosporium. It is concluded that Pleonosporium cannot stand as a genus on its polysporangiate character alone, so the tetrasporangia- and polysporangia-bearing genus Mesothamnion Boergesen as well as the tetrasporangia-bearing genus Compsothamnionella Itono are combined with Pleonosporium Naegeli. A new species of Pleonosporium, P. callicladum, is described from Natal. © 1985 The British Phycological Society.