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Dasya baldockii Parsons & Womersley, sp. nov.

Phylum Rhodophyta – Order Ceramiales – Family Dasyaceae


Dasya villosa var. ramulosa Harvey 1863, synop.: xxii. Lectotype selected here: "No. 58, Garden Island, October 1859, G.C(lifton)", annotated in Harvey's hand "Dasya villosa H. var. ramulosa", TCD. Silva et al. 1996: 435. Sonder 1881: 36.

Thallus (Fig. 198A) dark red-brown, soft and mucilaginous, 10–35 cm high, with 1–3 corticated axes 1–2.5 mm in diameter, much and irregularly branched, densely covered by basally branched, attenuate, monosiphonous filaments, but occasionally denuded at the base. Holdfast discoid; epilithic. Structure. Pericentral cells (Fig. 198B) 5, not obvious in transverse sections of the older axes, heavily corticated by rhizoidal filaments internally and externally to the pericentral cells. Pseudolaterals one per segment, 1–2 mm long, with 3–5 subdichotomies every 2 (1–3) cells on any filament giving 10–20 ultimate branches, distinctly attenuate from the base to beyond the last subdichotomy and then slightly attenuate as an ultimate unbranched filament. Adventitious monosiphonous filaments common, similar to young pseudolaterals, arising from the upper portion of pericentral cells 1 and 3, beginning at about 11 segments from the apex, and also from the later formed cortical cells; occasionally the adventitious filaments are arranged in apparent whorls. Intercalary cell divisions absent or rare. Basal cells of pseudolaterals and adventitious filaments (40–) 50–80 µm in diameter, L/D 0.5–1.5; cells after the last subdichotomy 15–30 µm in diameter, L/D 3.5–8; cells of ultimate filament 10–20 µm in diameter, L/D 7–20. Lateral axes arising from the basal cell of the first branch of an adventitious monosiphonous filament. Rhodoplasts discoid to elongate.

Reproduction: Gametophytes dioecious. Procarps borne spirally on a polysiphonous, usually adventitious, axis. Carposporophytes with a basal fusion cell, much branched gonimoblast, and clavate to lacrimiform carposporangia, formed apically and laterally in terminal clusters. Cystocarps (Fig. 198C) sessile on lateral axes, occasionally appearing almost terminal, urceolate, 950–1700 µm in diameter, with a distinct neck 0.2–0.4 (–0.5) the diameter of the cystocarp in length; pericarp 3–4 cells thick, outer cells irregularly placed. Spermatangial branches (Fig. 198D) sessile or on a 1–2-celled monosiphonous stalk, on the lower branches of both pseudolaterals and adventitious monosiphonous filaments, elongate-cylindrical, 600–1000 µm long and 80–95 µm in diameter, with 15–25 fertile segments and a 4–9 celled apical filament.

Stichidia (Fig 198E) on the lower branches of both pseudolaterals and adventitious monosiphonous filaments, cylindrical, rarely branched once at the base, sessile or on a 1–2-celled monosiphonous stalk, 200–800 µm long and 110–150 km in diameter, with 10–25 fertile segments each with (5–) 6–7 pericentral cells all of which become fertile. Each tetrasporangium with (2–) 3 cover cells (Fig. 198F) which are irregular to rectangular in shape and cover about half the sporangium, later becoming more elongate but rarely dividing.

Type from N side of Althorpe I., S. Aust., 9–12 m deep (Baldock, 4.i.1964). Holotype (tetrasporangial) and isotype (female) in AD, A27233.

Selected specimens: Point Clune, Rottnest I., W. Aust., 13m deep (Millar, 6.xii.1984; AD, A56296). Point Peron, W. Aust., drift (Parsons, 15.xi.1968; AD, A33375). St Francis I., Isles of St Francis, S. Aust., 19–20m deep (Shepherd, 6.i.1971; AD, A37986). Elliston, S. Aust., 10–11 m deep on limestone in centre of bay (Shepherd, 20.x.1969; AD, A35035). Edithburg, S. Aust., 1–4m deep (Prud'homme van Refine, 14.x.1988; AD, A59277). Shell rock, West I., S. Aust., 5–8 m deep (Shepherd, 28.xii.1965; AD, A30423). Vivonne Bay, Kangaroo I., S. Aust., 1–2 m deep on jetty pylon (Kraft, 19.i.1974; AD, A53345).

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

Distribution: Rottnest I., W. Aust., to West I., S.Australia

Taxonomic notes: Etymology: named for Mr Robert N. Baldock who has studied the Griffithsieae of southern Australia and who collected the type specimens of this species.

D. baldockii occurs in the sublittoral, on limestone or wooden jetty piles, 1–25 m deep, only known from late spring and early summer. It is closely related to D. kraftii, with which it sometimes occurs. The pseudolaterals and adventitious monosiphonous filaments of both species taper relatively distinctly from the basal cells to after the last subdichotomy. In D. kraftii however there are occasional intercalary divisions in the ultimate branches of these filaments, indicated by pairs of half-length cells and dividing cells. In D. baldockii the cells of the ultimate filaments continue to elongate as they increase in age and only rarely are half-length cells seen. The stichidia also differ, those of D. baldockii having 6–7 pericentral cells and tetrasporangia compared with 5 in D. kraftii. The cover cells are more prominent in D. baldockii and tend to be more obloid and palisade-like than those of D. kraftii, which are narrower and divide once or twice. The spermatangial branches are ovoid to ellipsoid in D. kraftii and long and cylindrical in D. baldockii. The cystocarps of D. baldockii are larger and consequently more prominent than those of D. kraftii.


HARVEY, W.H. (1863). Phycologia Australica. Vol. 5, Plates 241–300, synop., pp. i-lxxiii. (Reeve: London.)

SILVA, P.C., BASSON, P.W. & MOE, R.L. (1996). Catalogue of the Benthic Marine Algae of the Indian Ocean. (University of California Press: Berkeley, Los Angeles & London.)

SONDER, O.W. (1881). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)

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. 198.

Figure 198 image

Figure 198   enlarge

Fig. 198. Dasya baldockii (A–C, E, F, AD, A27233; D, AD, A42583). A. Habit of type. B. Transverse sections of young branches. C. A cystocarp. D. A spermatangial branch. E. Stichidia. F. Stichidia showing cover cells.

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