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Electronic Flora of South Australia Genus Fact Sheet

Genus HYPOGLOSSUM Kützing 1843: 444

Phylum Rhodophyta – Family Delesseriaceae

Thallus usually erect, mostly 5–20 cm high, with flat (usually), elongate blades arising from the midrib of older blades, monopodially developed (sympodial in H. revolutum), monostromatic apart form the midrib; lateral veins absent; holdfast discoid, usually epilithic. Structure. Apical cells obconical, segmenting to form an axial filament of cells with 2 lateral pericentral cells followed by 2 transverse pericentral cells, the lateral cells forming second-order cell rows with all or some cells forming third-order rows, with all rows reaching the blade margin. Blade margin with or without fourth-order rows, entire or serrate, or with fimbriate uniseriate extensions. New branches arise endogenously from the axial cells. Midrib becoming corticated and forming a subterete stipe below as the blade wings are lost.

Reproduction: Gametophytes dioecious. Procarps borne on transverse pericentral (supporting) cells on both sides of the blades, with 2 sterile groups and a 4-celled carpogonial branch. Carposporophyte with a basal fusion cell, much branched gonimoblast, and short chains of ovoid carposporangia maturing sequentially. Cystocarps ovoid to urceolate, sessile to stipitate, ostiolate and sometimes with a conspicuous neck; pericarp formed by erect filaments with 1–3 layers of outer cortical cells. Spermatangial sori on both sides of young blades, usually with sterile midrib and margin, with the primary cells cutting off initials each of which produce several spermatangia.

Tetrasporangial sori on smaller blades, with tetrasporangia cut off from several inner second- and third-order cells, occasionally from lateral (or even transverse) pericentral cells, and often from cortical cells, the sorus containing sporangia of different ages and covered by a cortex 1–2 cells thick.

Lectotype species: H. woodwardii Kützing 1843: 444 [= H. hypoglossoides (Stackhouse) Collins & Hervey 1917: 116]. See Kylin 1923, p. 81, fig. 52; Maggs & Hommersand 1993, p. 195, fig. 63.

Taxonomic notes: A genus of about 25 species (Wynne 1989a), with 6 on southern Australian coasts, monographed by Womersley & Shepley (1982).


COLLINS, F.S. & HERVEY, A.B. (1917). The algae of Bermuda. Proc. Am. Acad. Arts Sci. 53(1), 3–195.

KÜTZING, F.T. (1843). Phycologia generalis. (Leipzig.)

KYLIN, H. (1923). Studien über die Entwicklungsgeschichte der Florideen. K. Svenska Vetensk Akad Handl. 63, 1–139.

MAGGS, C.A. & HOMMERSAND, M.H. (1993). Seaweeds of the British Isles. Vol. 1. Rhodophyta. Part 3A, Ceramiales. (HMSO: London.)

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

WYNNE, M.J. (1989a). A reassessment of the Hypoglossum group (Delesseriaceae, Rhodophyta), with a critique of its genera. Helgol. Meeresunters. 42, 511–534.

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.


1. Branching of the thallus regularly sympodial, mainly from the adaxial (convex) side of revolute branches. Development of third-order cell rows within the tetrasporangial sorus suppressed compared with vegetative blades

H. revolutum

1. Branching of the thallus monopodial, irregularly abaxial or opposite. Development of third-order cell rows within the tetrasporangial sorus similar to that of vegetative blades (except H. dendroides)


2. Mature blades with all second-order cells producing third-order cell rows. Tetrasporangia not formed by transverse pericentral cells but often by cortical cells


2. Mature blades with only the inner second-order cells producing third-order cell rows. Tetrasporangia commonly formed by transverse pericentral cells, but not by cortical cells


3. Mature blade margin smooth or undulate, without serrations

H. heterocystideum

3. Mature blade margin distinctly serrate or with long cellular projections


4. Margin with regular spines or cellular projections, reflexed towards blade apex, derived from outgrowth of second-order cell rows

H. harveyanum

4. Margin with irregular spines (often becoming branched) derived from outgrowth of third- and fourth-order cell rows

H. armatum

5. Branching of thallus mainly abaxial; all blades of similar structure; margins with the outer 2 or 3 cells markedly smaller than inner cells and often produced in pairs from submarginal cells

H. protendens

5. Branching of thallus mainly opposite; ultimate blades usually considerably narrower and with fewer second-order cells than in earlier formed blades; margins with outer cells produced singly from submarginal cells and only slightly smaller than inner cells

H. dendroides

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