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Electronic Flora of South Australia Genus Fact Sheet

Genus ANOTRICHIUM Nägeli 1861: 397

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Griffithsieae

Thallus usually erect, tufted or with tufts arising from prostrate filaments (A. planatum), subdichotomous, adventitiously subsecund (A. tenue) or with whorls of short laterals (A. towinna), ecorticate or loosely clothed near the thallus base with decurrent, anastomosing rhizoids. Attached by rhizoids from the base or from branched haptera. Structure. Cells relatively small and elongate compared to Griffithsia, (40–) 200–600 (–900) µm in diameter and L/D 1.7–10; filaments usually without constrictions between cells; synchronic hair-like laterals in whorls near the thallus apex, or grouped adjacent to female fertile axes; rhodoplasts discoid, scattered or in chains; cytoplasm with small crystalline inclusions.

Reproduction: Gametophytes dioecious. Female axes lateral, adaxial, 3-celled, the upper 2 cells short-cylindrical, the lowest (hypogenous) becoming large and pyriform and lifting the carposporophyte from the constriction between vegetative cells into a prominent lateral position; procarp systems subapical, each consisting of a lateral, abaxial, sterile cell and adaxially a supporting cell bearing apically a sterile cell and a recurved, 4-celled carpogonial branch laterally; hypogenous cell bearing 1-celled, synchronic involucral branches in 1 (–2) whorls consisting of elongate, incurved cells forming a cupulate involucre. Spermatangia in ovoid-pyramidal heads, each single and terminal on a large, adaxial, cylindrical-clavate pedicel near the thallus apex or single, subterminal, and adaxial from the upper ends of each clavate pedicel of several synchronic whorls near the thallus apex (A. tenue var. thyrsigerum).

Tetrasporangia borne singly on pedicels in similar positions and patterns to the spermatangial heads, involucre absent, with prominent hyaline sheaths, tetrahedrally divided.

Type species: A. barbatum Nägeli 1861: 397.

Taxonomic notes: A genus of some 15 species, world wide in distribution, divided into two subgeneric groups by Baldock (1976, p.560) on the arrangement of spermatangial heads and tetrasporangia.


BALDOCK, R.N. (1976). The Griffithsieae group of the Ceramiaceae (Rhodophyta) and its southern Australian representatives. Aust. J. Bot. 24, 509–593.

NÄGELI, C. (1861). Beiträge zur Morphologie und Systematik des Ceramiaceae. Sber. bayer. Akad. Wiss. Jb. 1861, Vol. 1, pp. 297–415, Plate 1.

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

Author: R. N. Baldock

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


1. Thallus a loose mat of creeping axial filaments and subsecund lateral branches produced irregularly from the lower ends of axial cells; hair-like synchronic laterals prominent, attenuate, in whorls of 8–16, initiated simultaneously from the upper shoulders of cells near the apices of branches. Spermatangial heads in whorls of 4–8 and tetrasporangia in whorls of 8–10 (–14), borne singly, subterminally and adaxially on clavate, synchronic pedicels from the upper shoulders of cells near the thallus apex which bear also hair-like synchronic laterals (A. barbatum group)

A. tenue var. thyrsigerum

1. Thallus tufted, fastigiate or spreading; branching subdichotomous from upper ends of cells, often prolific, or with complanate lateral branches from creeping filaments (A. planatum) or with short divergent laterals of limited growth in whorls of 3 (–4) (A. towinna); hair-like synchronic laterals obscure, absent or readily shed, in groups of 1–3, adjacent to female structures. Spermatangial heads and tetrasporangia initiated successively in adaxial groups of 1–4, borne singly and terminally on pedicels (A. elongatum Group)


2. Main axes irregularly branched, with whorls of 3 (–4) divergent lateral branch tufts of restricted growth from most axial cells

A. towinna

2. Main axes bearing single, subdichotomous, fastigiate or spreading lateral branches


3. Thallus tufted, cells small and slender, in mid thallus 44–92 µm in diameter and L/D 5.5–9. Reproductive structures diminutive; carposporophyte 150–400 µm across, spermatangial heads including pedicels 170–200 µm high, tetrasporangia 50–90 µm in diameter

A. subtile

3. Thallus tufted or with irregular main axes and spreading, fastigiate or corymbose lateral tufts; cells of thalli with pronounced axes 220–900 µm in diameter and L/D 3–6, otherwise cells in mid thallus 220–450 µm in diameter and L/D 2–6; carposporophytes 250–700 µm across, spermatangial heads including pedicels 350–450 µm high, tetrasporangia 60–105 µm in diameter


4. Main axes bearing regular, alternating, spreading lateral tufts (appearing flabellate when pressed) with immediate and pronounced narrowing of filaments from axes to laterals; filament apices mucronate. Tetrasporangia single (rarely in pairs), adaxial in subdichotomies of laterals. (Small and sparsely branched plants intergrade morphologically with A. elongatum.)

A. licmophorum

4. Main axes subdichotomously branched or bearing irregular subdistichous or corymbose lateral tufts, with gradual narrowing of filaments from axes to laterals; filament apices often obtuse. Tetrasporangia single at first, later usually in adaxial clusters of 3–8


5. Thallus coarse textured; cells near the thallus apex short-cylindrical, L/D 1.6–1.8, filament ends obtuse; sterile thalli subdichotomously branched. Lower axes twisted together and loosely clothed with decurrent rhizoids, forming a rope-like mass reaching 1 cm across. Tetrasporangia adaxial and subsecund on cells of terminal and lateral, spreading, corymbose branches of short cells. (Small plants with fine filaments and open (lax) branching intergrade morphologically with A. elongatum and can only be diagnosed if fertile.)

A. crinitum

5. Thallus soft textured; cells near the thallus apex elongate, L/D 6–8, filaments acuminate; branching open (lax) with lateral tufts often well separated on main axes to regularly subdichotomous and dense. Lower axes free, or loosely twisted together, clothed only sparsely with decurrent rhizoids. Tetrasporangia adaxial on most cells near the apex of subdichotomous terminal and lateral branch tufts of elongate cells. (Plants with prolific and regular lateral tufts intergrade with A. licmophorum.)

A. elongatum

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