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Dasya wilsonis J. Agardh 1890a: 88.

Phylum Rhodophyta – Order Ceramiales – Family Dasyaceae

Selected citations: De Toni 1903: 1184. Falkenberg 1901: 624. Lucas 1912: 157. Lucas & Perrin 1947: 310. Wilson 1892: 165.


Pachydasya wilsonis (J. Agardh) J. Agardh 1890a: pl. 3 fig. 6.

Thallus (Fig. 200A) red-brown, not adhering well to paper on drying, 10–25 cm high, irregularly radially branched, with patent laterals on one to several linear, corticated, axes, densely covered throughout with basally branched, upwardly curved, relatively rigid, patent, monosiphonous pseudolaterals and adventitious filaments. Main axes irregularly radially branched usually at intervals of 0.5–2 cm; laterals and lesser branches 1–2 mm in diameter. Holdfast conical, 2–10 mm across, with a loose rhizoidal surface; probably epilithic. Structure. Pericentral cells 5, not obvious in sections of older branches (Fig. 200B, C) due to enlarged cells of the rhizoidal cortication. Pseudolaterals (Fig. 200D) one per segment, 0.8–1.4 mm long, basally branched every 1–2 cells with 1–2 (–3) subdichotomies giving 4–6 ultimate simple branches several cells long; basal cells 40–50 µm in diameter and L/D 1–1.5, increasing to 55–60 µm in diameter and L/D 1.5–2, then tapering to a small, apically rounded, terminal cell. Adventitious monosiphonous filaments simple or branched, similar to the pseudolaterals, arising from the upper part of pericentral cells and later from cortical cells. Intercalary divisions not seen in monosiphonous filaments. Rhodoplasts discoid.

Reproduction: Gametophytes unknown.

Stichidia (Fig. 200E, F) borne on the lower branches of both the pseudolaterals and adventitious monosiphonous filaments, on a 1–2 (–4)-celled monosiphonous stalk, ovoid to lanceoid, 100–400 µm long and 50–140 (–150) µm in diameter with 5–20 fertile segments each with 5 pericentral cells and (3–) 5 sporangia per whorl; whole sterile segments occasionally present within the fertile part. Tetrasporangia 25–35 µm in diameter, each with (2–) 3 cover cells which remain short, exposing most of the sporangium.

Type from Portsea, Port Phillip Heads, Vic. (Wilson 33, 31.i.1883); lectotype (here selected), LD, 43808. Syntypes: Western Port, Vic. (Wilson 57, 7.i.1885; LD, 43809). South Channel, Port Phillip, Vic. (Wilson 33, 26.i.1884; LD, 43810 and MEL. 1006692, 40 m deep).

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

Distribution: Known only from Backstairs Passage, S. Aust., and Port Phillip Heads and Western Port, Victoria.

Taxonomic notes: D. wilsonis was known only from the above 1883–1892 specimens of Wilson's in LD, L, M and MEL, one of which (MEL, 1006692) is recorded as from "20r deep (40 m). Of the several Wilson specimens in LD, only one is annoted "stichidia in hac vidi", and this is chosen as lectotype; others are considered syntypes. However, a further collection in 1997 from Backstairs passage, S. Aust., indicates that this is a deep water species where strong currents occur; however, only sparse tetrasporangial material is available, and study of further fertile material as well as the vegetative development and number of pericentral cells is needed.


AGARDH, J.G. (1890a). Till algernes systematik. Acta Univ. lund. 26(3), 1–125, Plates 1–3.

DE TONI, G.B. (1903). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 3, pp. 775–1521 + 1523–1525. (Padua.)

FALKENBERG, P. (1901). Die Rhodomelaceen des Golfes von Neapel und der angrenzenden Meeres-abschnitte. Fauna und Flora des Golfes von Neapel. Monogr. 26. (Friedlander: Berlin.)

LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)

LUCAS, A.H.S. (1912). Supplementary list of the marine algae of Australia. Proc. Linn. Soc. N.S.W. 37, 157–171.

WILSON, J.B. (1892). Catalogue of algae collected at or near Port Phillip Heads and Western Port. Proc. R. Soc. Vict. 4, 157–190.

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

Author: M.J. Parsons and 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

Illustration in Womersley Part IIIA, 1998: FIG. 200.

Figure 200 image

Figure 200   enlarge

Fig. 200. Dasya wilsonis (A, lectotype in LD, 43808; B–F, AD, A66983). A. Habit of lectotype. B. Transverse section of young branch. C. Transverse section of older axis. D. Two pseudolaterals. E. Part of a branch with pseudolaterals and adventitious filaments, one bearing a stichidium. F. Filament with small ovoid stichidium.

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