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Electronic Flora of South Australia Species Fact Sheet

Amoenothamnion minimum Wollaston 1968: 384, figs 36R–U, 37A–L.

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Heterothamnieae

Selected citations: Athanasiadis 1996: 182, fig. 90.

Thallus (Figs 87J, 88A) medium red, erect, 5–15 mm high, with several subdichotomous axes (Fig. 87J, L), each axial cell with 4 (–5) small, equal or unequal, whorl-branchlets. Attachment by multicellular rhizoids (Fig. 87M) from basal axial cells, becoming digitately branched on contact with host; epiphytic. Structure. Apical cells 6–8 µm in diameter and L/D 1–1.2, enlarging rapidly (Fig. 87L) to axial cells 60–100 µm in diameter and L/D 1–2 (–2.5), shorter near the base. Whorl-branchlets (90–) 100–150 µm and 4–5 cells long, branched from the basal cell (Fig. 87K) 3–4 times with 2–4 cells at each branching; basal cells markedly longer than next cell, 20–30 µm in diameter and L/D 1.5–2, with thick walls, tapering to terminal mucronate cells 7–11 µm in basal diameter and L/D 1–1.3 (including mucro), often also with small lateral (basal hair?) cells; gland cells absent or sparse (Fig. 87K), on terminal or subterminal cells of whorl-branchlets, ovoid, 6–8 µm in diameter. Lateral branches arise on axial cells close to apices. Cells uninucleate; rhodoplasts discoid to elongate in smaller cells, becoming ribbon like in larger cells.

Reproduction: Gametophytes probably dioecious. Carpogonial branches (Fig. 87N) borne on the basal (=supporting) cells of young whorl-branchlets, with apical growth of the axis then ceasing. Post-fertilization the supporting cell cuts off upwardly an auxiliary cell (Fig. 87O), with the upper central cell producing a terminal and then 3–5 lateral gonimolobes (Fig. 87P) 90–120 µm across with ovoid carposporangia 20–30 µm in diameter; fusion of cells below the carposporophyte occurs, and branches from the axial cell below surround the terminal carposporophyte (Fig. 88A). Spermatangial (Athanasiadis 1996, p. 182) clusters borne on basal and lower cells of whorl-branchlets.

Tetrasporangia (Fig. 88B) occur on the inner cells of whorl-branchlets, adaxially situated, sessile, subspherical, 30–45 µm in diameter, tetrahedrally divided.

Type from Stanley Beach, (2 km E of Pennington Bay), Kangaroo I., S. Aust., on Wrangelia abietina, drift (Wollaston, 7.ii.1956); holotype in AD, A20058.

Selected specimens: Elliston, S. Aust., on Dasyphila preissii, 7 m deep (Shepherd, 21.x.1970; AD, A37576). Pennington Bay, Kangaroo I.. S. Aust., drift (Womersley, 22.viii.1954; AD, A19736). Walkerville, Vic., on Heterosiphonia muelleri, drift (Sinkora A2654, 23.xi.1979; AD, A61053).

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

Distribution: Elliston, S. Aust., to Walkerville, Victoria.


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

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

Illustrations in Womersley Part IIIA, 1998: FIGS 87 J–P, 88A, B.

Figure 87 image

Figure 87   enlarge

Fig. 87.A–I. Amoenothamnion planktonicum (AD, A29292). A. Thallus with dichotomous branches. B. Apex with young dichotomous axes. C. Apex with initiating whorl-branchlets. D. A whorl-branchlet with 3 branches from basal cell, and bearing hairs and gland cells. E. Attachment rhizoids from basal cells of whorl-branchlets. F. Carpogonial branch on basal (supporting) cell enlarging to form an auxiliary cell. G. A mature carposporophyte. H. Spermatangial branches on basal cell of a whorl-branchlet. I. Whorl-branchlets with tetrasporangia. J–P. Amoenothamnion minimum (AD, A20058). J. Branches with whorl-branchlets. K. Whorl-branchlets from above (upper figure) and side view (lower figure). L. Apical branching to form a subdichotomy. M. Attachment rhizoids from lower axial cells. N. Apical branches, one bearing a carpogonial branch. O. Post-fertilization, with the central cell bearing the first gonimolobe cell. P. A developing carposporophyte. (All as in Wollaston 1968. courtesy of Aust. J. Bot.)

Figure 88 image

Figure 88   enlarge

Fig. 88. Amoenothamnion minimum (AD, A20058). A. Thallus with whorl-branchlets and carposporophytes. B. Thallus with whorl-branchlets bearing tetrasporangia. C–G. Leptokionion fastigiatum (C, AD, A33922; D, AD, A13032; G, H, AD, A33448). C. Habit. D. Branches with apices, laterals and whorl-branchlets. E. Apex with rapidly enlarging subapical cells and whorl-branchlets with gland cells. F. Apex with axial cells enlarging more gradually, and whorl-branchlets with gland cells on terminal cells. G. Spermatangial clusters on whorl-branchlets.

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