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FAMILY CERAMIACEAE Dumortier 1822: 73, 100

Phylum Rhodophyta – Order Ceramiales

Thallus erect, decumbent or prostrate, much branched laterally, subdichotomously or with whorl branchlets, with 1–8 periaxial cells from each axial cell, ecorticate or corticated by rhizoidal filaments, adventitious filaments or adherent small-celled filaments. Gland cells present or absent. Growth apical; synchronous laterals present in Griffithsia.

Reproduction: Gametophytes dioecious or occasionally monoecious; procarpic. Carpogonial branches 4-celled, with or without a separate supporting cell, borne on axial or periaxial cells or filaments, in some taxa with a sterile group on the supporting cell; supporting cell usually producing an auxiliary cell post-fertilization. Fusion cell present or absent, the carposporophyte naked (or with a loose involucre), developing gonimolobes with all cells, terminal cells, or chains of cells forming carposporangia. Spermatangial initials on outer cells of periaxial filaments or in specialised clusters or heads.

Tetrasporangia sessile or shortly pedicellate, solitary or in small clusters on periaxial cells or filaments, on cortical rhizoids or filaments or on outer cortical cells, tetrahedrally or cruciately/decussately divided, rarely dividing to octosporangia; polysporangia and propagules present in a few genera.

Mixed phase plants, with tetrasporangia and gametangia on the one plant, occasionally occur in some taxa.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Taxonomic notes: The Ceramiaceae is a large family, well represented on southern Australia coasts with some 22 tribes, 65 genera and 159 species (several other species are known to occur but have not been adequately collected). It is distinguished by the uniseriate branches often with periaxial (but not pericentral) cells and the naked carposporophytes and tetrasporangia.

The following key to the tribes of Ceramiaceae should be used with some caution. While some tribes are characterised by vegetative features, in others knowledge of reproductive structures, especially of the female system, is essential. Some genera also do not fit clearly into the tribe in which they are currently placed.


DUMORTIER, B.C.J. (1822). Commentationes Botanicae. Observations botaniques, dédiées à la Société d'Horticulture de Tournay. (Tournay.)

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


1. Cortication absent or by lax to dense rhizoidal filaments of elongate cells usually arising from the basal cells of lateral branches/-lets at least several cells below the apices, when present usually covering the axial cells with discrete filaments


1. Cortication from usually close to apices, nodal or complete, by closely appressed filaments, appearing pseudoparenchymatous, cortex generally bare of external filaments with most outer cells short and isodiametric


2. Whorl-branchlets opposite or whorled on indeterminate axes, in some taxa obscured by dense rhizoidal cortication


2. Branchlets alternate or irregular throughout, not obscured by rhizoidal cortication, with no more than slight opposite or whorled arrangement [except for involucral branchlets below carposporophytes or synchronous whorls in some Griffithsieae, e.g. Halurus, and also Ochmapexus (Radiathamnieae)]


3. Main axes and branches heavily corticated by lax descending rhizoids, whorl-branchlets irregularly much branched and adjacent whorls overlapping, whorls often indistinct


3. Main branches not or relatively slightly corticated, with clearly defined whorls (or opposite pairs) of whorl-branchlets closely adjacent or clearly separated


4. Branching opposite on indeterminate axes, irregular in whorl-branchlets; gland cells present. Carpogonial branches scattered on cells of determinate or indeterminate branches, carposporophytes discrete, compact; tetrasporangia cruciately or decussately divided


4. Indeterminate axes and branches with 2 opposite whorl-branchlets (obscured behind apices) or (4–) 5 whorl-branchlets; gland cells absent; Carpogonial branches on successive axial cells or on pilose outer cortical filaments; carposporophytes incorporating whorl-branchlet filaments or discrete; sporangia tetrahedrally divided


5. Indeterminate axes and branches with (4–) 5 irregularly branched whorl-branchlets per axial cell. Carpogonial branches borne on successive axial cells near apices of indeterminate branches; carposporophytes incorporating terminal parts of fertile branches, with gonimoblast filaments intermingled with sterile whorl-branch filaments


5. Indeterminate axes and branches with 2 opposite, alternately branched, whorl-branchlets per axial cell, opposite branchlets rapidly obscured by dense cortication. Carpogonial branches borne on branched pilose outer cortical filaments; carposporophytes discrete, compact


6. Whorls of whorl-branchlets usually closely adjacent on the indeterminate branches, forming more or less linear branches with even contours; gland cells present or absent


6. Whorls of whorl-branchlets clearly separated on the indeterminate branches, giving irregular or moniliform contours; gland cells usually present, parallel or angled to the bearing cell and broadly attached to it


7. Whorl-branchlets in whorls of 3 or 4, formed in spiral or opposite sequence


7. Whorl-branchlets in whorls of 5 or 6, formed alternately or in opposite groups of 3


8. Thalli usually 5–20 cm high; gland cells absent. Sterile procarp cells producing an inner involucre of free filaments around the carposporophyte; carposporangia terminal on gonimoblast filaments; tetrahedral sporangia or polysporangia


8. Thalli usually 0.5–4 cm high (Macrothamnion and some Pterothamnieae 5–20 cm high); gland cells usually present. Sterile procarp cells not producing an involucre around the carposporophyte; most cells of carposporophyte forming carposporangia; tetrasporangia tetrahedrally or cruciately/decussately divided


9. Thalli usually ecorticate; gland cells absent or on short, 2–3-celled branchlets or terminal on rachides; whorl-branchlets when branched usually distichous. Carpogonial branches successive on basal cells of relatively normal whorl-branchlets below indeterminate branch apices or on shorter opposite branchlets; carposporophytes without an involucre; tetrasporangia lateral or terminal on whorl-branchlets


9. Thalli with lower axes corticate with rhizoids or ecorticate; whorl-branchlets usually not distichously branched (except in Ballia); gland cells absent or present but not on short 2–3-celled branchlets; carpogonial branches on basal cells of normal or reduced whorl-branchlets, carposporophytes with or without an involucre; tetrasporangia on cells of normal or reduced whorl-branchlets or on special branches thereof


10. Gland cells present, on short, 2–3 celled, branches or terminal on whorl-branchlets; whorl-branchlets distichous or decussate on indeterminate axes, usually branched; carpogonial branches on basal cells of normal whorl-branchlets; tetrasporangia mostly lateral on whorl-branchlets, cruciately or decussately divided


10. Gland cells absent; whorl-branchlets always distichous on axes, simple or with few branches; carpogonial branches on opposite, shorter, whorl-branchlets; tetrasporangia mostly terminal on whorl-branchlets, irregularly tetrahedrally divided.


11. Thalli mostly relatively large (5–20 cm high), lower axes usually corticated with rhizoids, gland cells present (touching only the bearing cell) or absent; carpogonial branches on basal rachis cells of whorl-branchlets; carposporophytes with an involucre; tetrasporangia on cells of whorl-branchlets or on branch systems, decussately divided


11. Thalli mostly relatively small, 0.2–4 (–10) cm high; lower axes ecorticate; whorl-branchlets usually not distichously branched; gland cells usually present, touching the bearing cell and often the next outer cell. Carpogonial branches on basal cells of reduced (2–4 cells long) whorl-branchlets, 1–3 (–4) on each of one or two axial cells near each indeterminate branch apex; carposporophytes without a distinct involucre; tetrasporangia on normal whorl-branchlets, tetrahedrally or obliquely divided


12. Cells relatively small, mostly < 150 µm in diameter (apart from older axial cells), uninucleate or multinucleate; propagules absent; procarps subapical on short or several-celled axes or on intercalary cells of normal axes


12. Cells large, lower cells usually over (100–) 150 m in diameter (except some Monosporeae), multinucleate; procarps subapical on short axes


13. Thalli small (less than 2 cm high), ecorticate; propagules present (Monosporeae) or absent; procarps on subapical cells of short branches or on the basal cell of a short axial branch, with single auxiliary cells and carposporophytes


13. Thalli small to large, (1–) 2–20 (–30) cm high, ecorticate or corticate at least below; procarps on axial cells with twinned supporting and auxiliary cells and carposporophytes, or on subapical or lower cells of short apical or lateral branches


14. Thalli small, 0.5–2 (–7) cm high, epiphytic or epilithic, with prostrate and usually straight erect axes, simple or irregularly branched cells; cells multinucleate; branching irregularly lateral; spermatangia formed on initials in compact heads; tetrahedrally divided sporangia or polysporangia


14. Thalli minute (less than 3 mm high), epiphytic on Laurencia, or Caulerpa and other algae; with a single basal cell or complanate multicellular holdfasts; main axes curved, with unilateral laterals from the convex side; cells uninucleate; spermatangia formed directly from branch cells; tetrasporangia tetrahedrally divided


15. Thalli small to 20 cm high, ecorticate above and corticated or not on lower axes or branches; apical cell divisions transverse. Carpogonial branches on one of two periaxial (supporting) cells on intercalary cells of indeterminate axes or laterals, with both periaxial cells producing auxiliary cells and "twinned" carposporophytes; procarps without sterile cells; spermatangia on branched filaments or small clusters


15. Thalli 5–20 (–50) cm high, heavily corticated from near the apices or below, or with a network of filaments; apical cells divisions more or less transverse or oblique and alternating; procarps with a single carpogonial branch and auxiliary cells, on the subapical or a lower axial cell or on special 3–8-celled lateral branches, with sterile cells or axial cells below the procarp producing an involucre of filaments around the carposporophyte; spermatangia on heads


16. Branch apices usually emergent. Procarps (2–3) situated 2–5 cells below apices of few-celled lateral axes which may extend apically after fertilization, with sterile cells of procarp forming short branches around the carposporophyte or an involucre from lower cells but not becoming larger and rounded


16. Branch apices usually overtopped by lower branchlets. Procarps on subapical cells of special 3 (–5) celled fertile branches (if 5-celled, the upper 3 cells modified), with the apical and 2 lateral lower sterile cells larger and rounded, with the carposporophyte appearing terminal on short lateral branches, with a lax involucre of short branches from axial cells below the procarp


17. Asexual ovoid, 1–3-celled, propagules present; upper (and often lower) cells less than 200 .tm in diameter; tetrasporangia or polysporangia present


17. Propagules absent; lower cells usually more than 200 µm in diameter; tetrasporangia only


18. Synchronous lateral branches absent; female axes 5–6 (–8) cells long with successive functional (4-celled) and non-functional (2-celled) carpogonial branches; carposporangia on slender gonimoblast processes, terminal, clavate


18. Synchronous lateral branches present; female axes 3 cells long, with a subapical carpogonial branch; carposporangia ovoid to clavate, formed from most cells of the carposporophyte


19. Branching usually pinnate, with alternate or opposite laterals lying in one plane, usually alternately developed; cortication filamentous to pseudoparenchymatous, irregularly developed on the axial cells


19. Branching radial or complanate (pinnate in some Ceramium spp.), cortication from whorls of nodal periaxial cells forming acropetal (and usually basipetal) filaments mostly of short cells closely appressed to the axial cells


20. Indeterminate axis cells with 2 or 4 periaxial cells, producing alternate or opposite distichous determinate branches. Tetrasporangia on ultimate, ecorticate branchlets


20. Indeterminate axis cells with 4–6 (–10) periaxial cells and filaments from each axial cell, lateral ones developing into alternate, distichous, determinate branches. Tetrasporangia derived from surface cortical cells or borne on filaments or in branchlets


21. Cortication of indeterminate branches complete, consisting of alternating bands of long and short cells, longitudinally and transversely aligned; indeterminate branches bearing lateral or whorled (or single) elongate determinate ramelli with narrow nodal cortication only and bearing tetrasporangia at the nodes


21. Cortication of all branches arising nodally, closing completely or leaving a clear gap; elongate determinate ramuli absent; tetrasporangia from periaxial or cortical cells


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