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Genus CHONDRIA C. Agardh 1817: xviii, nom. cons.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Chondrieae

Thallus usually erect, rarely prostrate or free-floating, much branched irregularly radially or unilaterally, rarely subdistichously, with or without one to a few percurrent axes; a few species with tendrils, axillary branches often present; branches terete or compressed, young branches basally constricted. Some species with swollen, bulbous, sterile storage organs. Attachment by discoid holdfasts or haptera from stolons; epilithic or epiphytic. Structure. Apices of branches depressed or rounded, or tapering, with an apical filament usually 10–20 cells long, the subapical cells cutting off 5 pericentral cells in alternating order and branched trichoblasts. Pericentral cells of similar length to axial cells except near apices of tetrasporangial thalli, producing 2–5 series of di- to quadrichotomous branchings, expanding rapidly to form the rounded ends of branches; pericentral cells remaining clear throughout the thallus, cortex of compact, ovoid cells with the epidermal cells ovoid or angular to elongate in surface view. Pericentral and often the inner cortical cells of most species developing wall thickenings of various forms often characteristic of the species. Rhizoids usually formed from pericentral and inner cortical cells, sparse to dense around these cells in larger branches. Secondary cortex absent or present on the lower axes by proliferation of the epidermis.

Reproduction: Gametophytes dioecious. Procarps borne on a lower cell of trichoblasts, with the fifth-formed pericentral (supporting) cell bearing a 4-celled carpogonial branch and lateral and basal sterile cell groups; auxiliary cell cut off post-fertilization or in some species the supporting cell acting as auxiliary cell. Carposporophytes with a basal fusion cell and branched gonimoblast with clavate terminal carposporangia, replaced from lower cells. Cystocarps ovoid to slightly urceolate, in some species with a basal spur developed from trichoblast cells above the supporting cell; pericarp ostiolate, with 9–18 erect filaments arising pre-fertilization from adjacent pericentral cells, each cell with 2–3 outer pericentral cells and ecorticate or not. Spermatangial plates flat, discoid or slightly lobed, developed from the whole or a basal branch of a trichoblast, with the primary cells producing a layer of initials each cell of which cuts off 2–4 spermatangia, and with a sterile margin 1–3 cells broad.

Tetrasporangia developed in lesser branchlets, cut off singly from near the outer ends of 1–3 radially elongate pericentral cells per axial cell, covered by the outer cortex and epidermal cells.

Type species: C. tenuissima (Withering) C. Agardh 1817: xviii [= C. capillaris (Hudson) Wynne 1991: 317].

Taxonomic notes: A genus of 40–50 species, well represented on southern Australian coasts with 15 species. This account is based on the revision by Gordon-Mills & Womersley (1987), which presented several taxonomic hypothesis for their separation, most of which need further testing.

Chondria is superficially similar to Laurencia, but differs in that the pericentral cells remain clear in transverse sections throughout the thallus, the flat spermatangial plates contrast with those of Laurencia, and the tetrasporangia are cut off from the pericentral cells only, not from the ends of pericentral cells or from outer cortical cells as occurs in Laurencia.

Gordon-Mills & Womersley (1984b, 1987) have pointed out the importance of the cell wall thickenings, stained with 2 x 10‰ aqueous ruthenium red, in distinguishing many of the species of Chondria.

Chondria dasyphylla was recorded from southern Australia by Harvey (1855a, p. 539) and later authors, but rejected as an Australian species by Gordon Mills (1987); Australian references to C. dasyphylla probably apply to several species, including C. curdieana and C. harveyana. Similarly, early records of C. tenuissima from Australia are usually uncertain.


AGARDH, C.A. (1817). Synopsis Algarum Scandinaviae. (Berling: Lund.)

GORDON-MILLS, E.M. & WOMERSLEY, H.B.S. (1984b). Cell wall thickenings in the taxonomy of Chondria and Husseyella (Rhodomelaceae, Rhodophyta) from southern Australia. Hydrobiologia 116/117, 224–226.

GORDON-MILLS, E.M. & WOMERSLEY, H.B.S. (1987). The genus Chondria C. Agardh (Rhodomelaceae, Rhodophyta) in southern Australia. Aust. J. Bot. 35, 477–565.

HARVEY, W.H. (1855a). Some account of the marine botany of the colony of Western Australia. Trans. R. Jr. Acad. 22, 525–566.

WYNNE, M.J. (1991). A change in the name of the type of Chondria C. Agardh (Rhodomelaceae, Rhodophyta). Taxon 40, 316–318.

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

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.


1. Thallus largely prostrate, attached to host algae by multicellular haptera from the lower side of compressed axes; cystocarps with the adaxial wall adnate to the bearing branch

C. infestans

1. Thallus largely erect, epiphytic or epilithic; axes terete or compressed; cystocarps not adnate to the bearing branch


2. Thallus branches terete throughout


2. Thallus branches mostly compressed or compressed below


3. Lesser branches under 250 µm in diameter


3. Lesser branches mostly over 250 µm in diameter

5 ...

4. Apices pointed, branching radial; cystocarps with a pointed spur; spermatangial plates with few sterile marginal cells; thallus epiphytic or loose-lying

C. angustissima

4. Apices slightly depressed, branching unilateral; cystocarps without a spur; spermatangial plates with a row of sterile marginal cells; epilithic or on artificial substrates

C. arcuata

5. Swollen storage organs present at base of axes or on upper branches

C. bulbosa

5. Swollen storage organs absent


6. Epidermal cells short, L/D 1–1.5 (–2.5); thallus robust, ultimate branchlets 1–1.5 mm in diameter, axillary branches frequent

C. incurva

6. Epidermal cells elongate, L/D 1.5–10 (–17); thallus robust or slender, ultimate branchlets less than 1 mm in diameter, axillary branches present or absent


7. Cell wall thickenings elaborate, forming circular branches with extensions, becoming highly lobed and almost reticulate

C. hieroglyphica

7. Cell wall thickenings present or absent, if present as apical caps or semicircular bands, occasionally lobed in lower axes but not reticulate


8. Lateral branches mostly unilateral and adaxial

C. subsecunda

8. Lateral branches irregularly radial


9. Thallus usually with ends of lateral branches forming curled tendrils; thallus epiphytic or loose lying

C. capreolis

9. Ends of lateral branches straight, not tendril-like


10. Apices attenuate to bluntly pointed; cell wall thickenings as discrete caps on both upper and lower ends of pericentral and inner cortical cells; spermatangial plates with a sterile margin 2–3 cells broad


10. Apices rounded or depressed; cell wall thickenings mainly as caps on the upper ends of pericentral and/or inner cortical cells; spermatangial plates with a sterile margin one cell broad


11. Axillary branching present; cell wall thickenings present; epidermal cells L/D mostly 2–5; cystocarps without a spur; spermatangial plates with a 2 (–3)-cell broad sterile margin; tetrasporangia 180–250 µm in diameter


11. Axillary branching absent or occasionally present; cell wall thickenings absent or as upper end caps; epidermal cells L/D (1.5–) 5–17; cystocarps with a spur; spermatangial plates with a single row of marginal sterile cells; tetrasporangia 120–150 µm in diameter


12. Axillary branches profuse; cell wall thickenings as caps on upper ends of pericentral and inner cortical cells, later as circular bands

C. subfasciculata

12. Axillary branches moderate; cell wall thickenings as brands around pericentral and inner cortical cells, becoming hooked

C. curdieana

13. Thallus usually 10–40 cm high, loosely branched, dark red to brown-red, cell wall thickenings absent; epidermal cells 10–15 µm broad, L/D 9–17

C. harveyana

13. Thallus usually 3–18 cm high, medium red to brown-red, cell wall thickenings absent or as caps on upper end of cells; epidermal cells (15–) 20–25 µm broad, L/D 1.5–7 (–12)

C. succulenta

14. Thallus 2–6 cm high; terete near apices, compressed in mid and lower parts, branches (300–) 500–800 µm broad

C. lanceolata

14. Thallus usually 5–30 cm high; compressed throughout (except at base), branches 0.8–3 mm broad


15. Apices usually pointed; main branches 0.8–1.5 mm broad; epidermal cells angular, 15–35 across

C. foliifera

15. Apices rounded, or depressed; main branches 1.5–2 (–3) mm broad; epidermal cells rounded, (20–) 30–60 (–85) µm across

C. incrassata

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