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Electronic Flora of South Australia Genus Fact Sheet

Genus CODIUM Stackhouse 1797: xvi, xxiv

Phylum Chlorophyta – Order Codiales – Family Codiaceae

Thallus medium to dark green, epilithic, applanate or pulvinate and often lobed, or subglobose, or erect and simple to repeatedly subdichotomous, from a few cm across when applanate to about 1 m high with branches 3–10 mm in diameter in erect dichotomous species. Thallus diploid, with an internal medulla of slender, branched, interwoven filaments and a peripheral cortex of swollen utricles. Utricles with (1–) 2–4 slender, basal medullary filaments, one of which in many species is largely closed by a plug of wall material, situated near to the utricle base; new utricles arising from medullary filaments or in some species from the lower part of primary utricles. Apex of utricle wall characteristically thickened and internally sculptured in some species. Chloroplasts numerous, discoid, without pyrenoids. Colourless or pale hairs produced in most species from the utricles shortly below their apices, caducous but usually leaving a distinct scar. Gametangia borne laterally on the utricles, usually with a very short pedicel, elongate-ovoid, discharging anisogametes apically; plants usually dioecious, fertile usually in winter.

Type species: C. tomentosum (Hudson) Stackhouse [= C. dichotomum (Hudson) Gray].

Taxonomic notes: A genus of some 80 species, present in most seas and well represented with 16 species on southern Australian coasts.


STACKHOUSE, J. (1797). Nereis Britannica... Fasc. 2, ix-xxiv, 31–70, Plates ix-xii. (Bath.)

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (31 May, 1984)
The Marine Benthic Flora of Southern Australia
Part I
©Board of the Botanic Gardens and State Herbarium, Government of South Australia


1. Thallus applanate or subglobose


1. Thallus erect, simple or dichotomously branched


2. Thallus applanate or pulvinate, often lobed


2. Thallus subglobose


3. Utricles mostly less than 100 µm in diameter


3. Utricles mostly greater than 100 µm in diameter


4. Utricles devoid of hairs

C. dimorphum

4. Older utricles with hairs (or hair scars)


5. Utricles 600–1300 µm long, regularly and conspicuously capitate, apices symmetrical

C. capitulatum

5. Utricles 435–800 (–1150) µm long, irregularly constricted below the apex, apices asymmetrical

C. lucasii

6. Utricles in small clusters, apical wall thickened into a galeate cap to 56 µm thick

C. perriniae

6. Utricles in large clusters, apical wall thin or moderately thickened (-32 µm)

C. spongiosum

7. Utricles mostly 450–1000 µm in diameter near their apex

C. mamillosum

7. Utricles mostly 90–125 µm in diameter near their apex

C. pomoides

8. Thallus simple or once-divided, broad and flat, felt-like

C. laminarioides

8. Thallus dichotomously to laterally branched, branches terete or slightly compressed near branchings


9. Utricles not mucronate


9. Utricles mucronate


10. Utricle apices with spinous internal trabeculae

C. silvae

10. Utricles without spinous trabeculae


11. Utricles often longer than 1 mm


11. Utricles always shorter than 1 mm


12. Utricles with galeate thickening at apex

C. galeatum

12. Utricles with thin or slightly thickened apical wall, not galeate

C. duthieae

13. Medullary filaments usually with plugs close to point of departure from utricle

C. harveyi

13. Medullary filaments with plugs conspicuously distant from point of departure from utricle


14. Utricles prominently introrsely umbonate

C. muelleri

14. Utricles not introrsely umbonate

C. australicum

15. Utricles mostly longer than 1 mm

C. fragile

15. Utricles 475–680 ,.an long

C. spinescens

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