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Hypoglossum protendens (J. Agardh) J. Agardh 1898: 189.

Phylum Rhodophyta – Family Delesseriaceae

Selected citations: De Toni 1900: 693. Kylin 1924: 9. Lucas 1909: 36. Shepherd & Womersley 1970: 135. Silva et al. 1996: 459. Womersley & Shepley 1982: 336, figs 2B, 8.


Delesseria protendens J. Agardh 1894: 67.

Thallus (Fig. 20A) medium red, 5–20 cm high, with one to several main axes, usually widely spreading and much branched, mainly abaxially. Base of plant (holdfast and about 1 cm of upright stipe below the point of branching) probably perennial. Main blades becoming denuded below, leaving the heavily corticated midrib as an axis. Mature blades 3–5 mm broad throughout and often with upper curved ends; young blades (Fig. 20B) narrower and tapering to a conical apex, becoming rounded when mature. Holdfast small, discoid; epilithic. Structure. Apical development with only the inner (3–) 4–8 second-order cells producing third-order cell rows (Fig. 16F), the mature blades with up to 25 elongate (L/D about 5) cells between midrib and margin. Second- and third-order cell rows run obliquely (about 45° to midrib) across the blade. Margin of mature blade smooth to undulate (Fig. 20B, C), usually with 2 or 3 rows of small isodiametric marginal cells often cut off in pairs from larger submarginal cells; some of the small marginal cells extend to 2 or 3 cells long and project irregularly along the margin (Fig. 20D, G). Midrib becoming corticate on the lower half of the youngest blades by a central band of 6–10 longitudinal corticating filaments. Mature cells multinucleate; rhodoplasts discoid, becoming chained.

Reproduction: Gametophytes dioecious. Procarps not observed. Carposporophyte with carposporangia formed terminally and usually singly from the sequentially maturing cells of the gonimoblast, ovoid to pyriform, 50–100 µm in diameter. Cystocarps (Fig. 20E) develop on either surface of the smaller blades, hemispherical when young, becoming massive, depressed globular and basally constricted, 1.2–3 mm across with virtually no neck and a small ostiole; pericarp 5 or 6 cells thick. Spermatangial sod (Fig. 20F) covering the blades on either side of the midrib but with sterile areas of varying width along the margins and adjacent to midrib; sterile rows or patches also usually occur within the spermatangial area, running from midrib to margin, especially as sod develop.

Tetrasporangial sod well defined, ovate to elongate and tapering (Fig. 20G), covering the midrib and up to half the marginal width, and with a coherent layer (becoming 2 or 3 cells thick) of cortical cells over the whole sorus. Cortical cells are present when tetrasporangia are initiated. Tetrasporangia first develop acropetally from the lateral pericentral cells, giving two distinct rows of sporangia, then spread laterally from other second- or third-order cells, also developed from both abaxial and adaxial residual transverse pericentral cells though only occasional tetrasporangia mature in these positions. Tetrasporangia do not originate from cortical cells and are usually regularly arranged in the sorus, but sometimes differ in their degree of maturity; tetrasporangia 100–180m in diameter.

Type from Port Phillip Heads, Vic. (Wilson); lectotype in Herb. Agardh, LD, 31572.

Selected specimens: Fremantle, W. Aust. (H. Yabu, 15.xii.1965; AD, A30634). Oedipus Point, West I., S. Aust., 16 m deep (Shepherd, 8.x.1966; AD, A30812-"Marine Algae of southern Australia" No. 403). Seal Rock, West I., S. Aust., 25 m deep (Shepherd, 15.iv.1967; AD, A31952). Amphitheatre Rock, West I., S. Aust., 20–22 m deep (Shepherd, 1.i.1969; AD, A33246). West I., S. Aust., 25 m deep (Shepherd, 29.i.1973; AD, A42964). Investigator Strait, S. Aust., 35 m deep (Watson, 14.i.1971; AD, A38209). Port Phillip Heads, Vic. (Wilson, 13.i.1883; MEL, 31572 and 11.i.1884; MEL, 10034).

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

Distribution: Fremantle and the Recherche Arch., W. Aust., to Port Phillip Heads, Victoria.

Taxonomic notes: Hypoglossum protendens is based on Wilson specimens from Port Phillip Heads, Vic., which J. Agardh (1894, p. 67) had first referred to as D. revoluta major ?

H. protendens agrees with other species of Hypoglossum in that all third-order cell rows reach the thallus margin, but differs from most other species in that only the inner (3–) 4–8 second-order cells form third-order rows. The thallus margins are also characteristic, with small isodiametric cells, often two from each of the larger inner cells, and some of these small cells form short 1–3-celled outgrowths (Fig. 20D). The tetrasporangial sori are particularly well defined with a cortex becoming 2 or 3 cells thick and a coherent outer layer of cortical cells; no clear cases have been seen of tetrasporangia originating from cortical cells. Tetrasporangia derived from the transverse pericentral cells do not always mature.

H. protendens resembles H. dendroides (see below) in that not all second-order cells form third-order rows, and in the formation of tetrasporangia from the transverse pericentral cells as well as second-order and third-order cells but not from cortical cells. However, H. protendens differs clearly from H. dendroides in having typical thallus development in fertile blades, whereas the latter taxon bears only single rows of cells from the lateral pericentral cells in female and tetrasporangial blades.


AGARDH, J.G. (1894). Analecta Algologica. Cont. II. Acta Univ. lund. 30, 1–98, Plate 1.

AGARDH, J.G. (1898). Species Genera et Ordines Algarum. Vol. 3, Part 3 - De dispositione Delesseriearum. (Gleerup: Lund.)

DE TONI, G.B. (1900). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 2. pp. 387–776. (Padua.)

KYLIN, H. (1924). Studien über die Delesseriaceen. Lunds Univ. Årsskr. N.F. Avd. 2, 20(6), 1–111.

LUCAS, A.H.S. (1909). Revised list of the Fucoideae and Florideae of Australia. Proc. Linn. Soc. N.S.W. 34, 9–60.

SHEPHERD, S.A. & WOMERSLEY, H.B.S. (1970). The sublittoral ecology of West Island, South Australia: 1. Environmental features and algal ecology. Trans. R. Soc. S. Aust. 94, 105–137, Plate 1.

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

WOMERSLEY, H.B.S. & SHEPLEY, E.A. (1982). Southern Australian species of Hypoglossum (Delesseriaceae, Rhodophyta). Aust. J. Bot. 30, 321–346.

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

Author: H. B. S. Womersley

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.

Illustrations in Womersley Part IIIA, 2003: FIGS 16F, 20.

Figure 16 image

Figure 16   enlarge

Fig. 16. A. Hypoglossum revolutum (AD, A37017)). Cell lineages, cells of second-order rows stippled. B, C. Hypoglossum heterocystideum (AD, A32138). B. Juvenile blade. C. Cell lineages, mid blade. D. Hypoglossum harveyanum (AD, A49090). Cell lineages, mid blade. E. Hypoglossum armatum (AD, A49380). Cell lineages, mature blade. F. Hypoglossum protendens (AD, A42964). Cell lineages, mid blade. G, H. Hypoglossum dendroides (AD, A37557). G. Blade apex. H. Sectional views of apices and formation of transverse pericentral cells (as in Womersley & Shepley 1982, courtesy of Aust. J. Bot.).

Figure 20 image

Figure 20   enlarge

Fig. 20. Hypoglossum protendens (A, D, G, AD, A38209; B, C, F, AD, A30812; E, AD, A42964). A. Habit. B. Blade with apex and young blades from midrib. C. Part of a mature blade. D. Margin of blade with 1-2-celled outgrowths. E. Blades with cystocarps. F. Blade with spermatangial sori. G. Blade with a tetrasporangial sorus. (A–D, F, G as in Womersley & Shepley 1982, courtesy of Aust. J. Bot.)

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