Electronic Flora of South Australia Genus Fact Sheet

Genus TRITHAMNION Wollaston 1968: 388

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Heterothamnieae

Thallus with prostrate and erect axes or entirely erect axes, attached by branched rhizoids; usually epiphytic. Axial cells each bearing 3 (occasionally 2 or 4) whorl-branchlets with one longer branchlet between two shorter branchlets, branchlet rachis cells with pairs of short branches, often with a pair of small terminal cells; basal cell of whorl-branchlet usually unbranched; gland cells sessile on subterminal to lower cells of the branches of the whorl-branchlets, cut off from subterminal cells. Lateral branches replacing, or extending from, the longer whorl-branchlets. Cells usually uninucleate.

Reproduction: Carpogonial branches on the basal cell of short, 2-celled branchlets on axial cells near branch apices, with the terminal cell appearing as a sterile cell on the supporting cell; carposporophytes with 4–6 rounded gonimolobes, surrounded by curved whorl-branchlets or lateral branches from below. Spermatangia unknown.

Tetrasporangia borne on cells of whorl-branchlets, sessile, ovoid to subspherical, tetrahedrally to sub-decussately divided.

Type species: T. gracilissimum Wollaston 1968: 389, fig. 38I–P.

Taxonomic notes: A genus of 4 species from southern Australia, and one [T. tenellum (Harvey) Wollaston 1968, p. 389] known only from Rottnest I., W. Australia; the latter, however, may be identical with T. aculeatum.

References:

WOLLASTON, E.M. (1968).Morphology and taxonomy of southern Australian genera of Crouanieae Schmitz (Ceramiaceae, Rhodophyta). Aust. J. Bot. 16, 217–417.

The Marine Benthic Flora of Southern Australia Part IIIC complete list of references.

Author: H.B.S. Womersley & E.M. Wollaston

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

KEY TO SPECIES OF TRITHAMNION

1. Thallus erect, clumped, attached by a rhizoidal holdfast from lower cells of erect axes; epiphytic on Caulerpa spp. and firm-surfaced algae.	T. vulgare
1. Thallus with prostrate axes bearing erect branches; epiphytic on various algae, or other substrates	2
2. Long whorl-branchlets 100–250 µm long, branchlets separate; axial cells 25–55 in diameter and L/D 4–6	T. gracilissimum
2. Long whorl-branchlets usually above 250 µm long, branchlets overlapping; axial cells 70–160 µm in diameter and L/D 1.5–4	3
3. Long whorl-branchlets upwardly curved and overlapping, short whorl-branchlets separate and 40–100 long; gland cells touching the bearing cell and abutting the next cell of a dichotomy	T. aculeatum
3. All whorl-branchlets overlapping, short whorl-branchlets 130–180 µm long; gland cells touching only the bearing cell	T. eubryanii

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