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Electronic Flora of South Australia Genus Fact Sheet

Genus OCHMAPEXUS Womersley, gen. nov.

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Radiathamnieae

Thallus small, epiphytic on Caulerpa longifolia and several other algae or epizoic, attached by complanately branched, pectinate, multicellular holdfasts, with a curved primary axis bearing unilaterally secondary branches on the convex side, branches oppositely or alternately branched, tapering slightly; lesser branches often also unilaterally branched. Cells uninucleate.

Reproduction: Female thalli unknown*. Male thalli doubtfully known; possible spermatangia cut off from cells of short lateral branchlets borne unilaterally on upper branches.

Tetrasporangia borne on short lateral branchlets, first terminally and then laterally or in opposite pairs, sessile, tetrahedrally divided.

Type (and only) species: 0. minimus (Harvey) Womersley, comb. nov.

Taxonomic notes: Ochmapexus is named for the distinctive holdfasts, ochma referring to holdfast and pexus to the comb-like arrangement.

Although sexual plants are little known, Ochmapexus agrees in general morphology with Radiathamnion but differs in hosts, in basal attachment, and in thallus details.

* AD, A67940, from Marion Bay, Yorke Pen., S. Aust., on Cystophona monilifera, drift (Womersley, 9.x.1998) shows carpogonial branches on the basal cells of branches of the laterals, but no later stages.

References: The Marine Benthic Flora of Southern Australia Part IIIC

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
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