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Gymnothamnion nigrescens (J. Agardh) Athanasiadis 1996: 204.

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Gymnothamnieae


Antithamnion nigrescens J. Agardh 1894a: 116. De Toni 1903: 1404. Lucas 1909: 51. Lucas & Perrin 1947: 353. Wollaston 1968: 300.

Thallus (Fig. 57A) probably 2–3 cm high, dark red-brown, complanately branched with slightly incurved apices and axes bearing irregular laterals, all axial cells bearing opposite branchlets becoming 8–14 cells and 500–900 µm long, simple or with short adaxial branches from their 2–5 basal cells, the lowest ones branched. Attachment probably by rhizoids. Structure. Apical cells 20–25 µm in diameter and L/D 2–3, dividing more or less transversely, increasing in axial cells to 80–130 µm in diameter and L/D 1–2, branchlets basally 35–50 µm in diameter, decreasing only slightly to apical cells 30–35 µm in diameter, cells basally L/D 1–1.5, mid cells L/D 1.5–2, apical cells L/D 1–1.5.

Reproduction: Unknown.

Type from Port Phillip Heads, Vic. (Wilson); holotype in Herb. Agardh, LD, 18128.

Distribution map based
on current data relating to
specimens held in the
State Herbarium of SA

Distribution: Only known from the holotype specimen.

While the habit agrees with Gymnothamnion, new collections and reproductive plants are needed to establish the position of G. nigrescens. It has apparently never been found since the original collection.


AGARDH, J.G. (1894a). Analecta Algologica. Cont. I. Acta Univ. lund. 29, 1–144, Plates 1, 2.

ATHANASIADIS, A. (1996). Morphology and classification of the Ceramioideae (Rhodophyta) based on phylogenetic principles. Opera Botanica No. 128, pp. 1–216.

DE TONI, G.B. (1903). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 3, pp. 775–1521 + 1523–1525. (Padua.)

LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)

LUCAS, A.H.S. (1909). Revised list of the Fucoideae and Florideae of Australia. Proc. Linn. Soc. N.S.W. 34, 9–60.

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

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

Illustration in Womersley Part IIIA, 1998: FIG. 57A.

Figure 57 image

Figure 57   enlarge

Fig. 57. A. Gymnothamnion nigrescens (slide of type fragment, AD, A 18386). Branching of axes, with opposite branchlets bearing adaxial branches. B–E. Gymnothamnion elegans (B–E, MELU, K9362; AD, A67815). B. Branched axes with opposite branchlets. C. Apex of axis with developing opposite branchlets. D. Mature axis and branchlets with procarps. E. Axis with short opposite branchlets bearing procarps.

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