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Order Halymeniales

Family Halymeniaceae

Genus Pachymenia J. Agardh

Thalli flat, foliose, incised or lobed, mucilaginous and slippery to cartilaginous, with discoid holdfast and little to no stipe. Structure multiaxial: cortex thick, with outer layer of radiating, branched filaments of somewhat elongated cells and inner layer of isodiametric cells that sometimes become stellate; medulla of sparse to dense irregular filaments, with or without refractice ganglionic cells. Life history with isomorphic sporophytes and gametophytes. Cystocarps with or without ostiole, immersed in thallus. Tetrasporangia excised from cortical cells, scattered and immersed in cortex, cruciately divided.

This genus is distributed widely in the Southern Hemisphere and comprises about 9 species. Some taxonomic uncertainly surrounds some of the species, and a number of species previously ascribed to the genus Aeodes (including the South African A. ulvoidea and A. orbitosa are now placed within Pachymenia (see Russell et al. 2009).

Key to the species


1a. Thalli rather cartilaginous, with thickened margins and sometimes double-margins; subtidal

Pachymenia cornea

1b. Thalli smooth, slippery, without thickened or double margins; usually intertidal

Pachymenia ulvoidea


References Pachymenia

Russell, L. K., Hurd, C. L., Nelson. W.A. & J. E. Broom 2009. An examination of Pachymenia and Aeodes (Halymeniaceae, Rhodophyta) in New Zealand and the transfer of two species of Aeodes in South Africa to Pachymenia. Journal of Phycology 45: 1389-1399.


Cite this record as:

Anderson RJ, Stegenga H, Bolton JJ. 2016. Seaweeds of the South African South Coast.
World Wide Web electronic publication, University of Cape Town,; Accessed on 26 February 2024.