Electronic Flora of South Australia Genus Fact Sheet

Genus DICTYOPTERIS Lamouroux 1809a: 332, nom. cons.

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Zonarieae

Thallus essentially complanate though sometimes twisted, subdichotomously to laterally branched, usually 10–40 cm long with branches 3–25 mm broad, with a prominent central midrib throughout, with or without fine veins in the lateral wing, attached by a matted rhizoidal holdfast. Growth by a small group of 3–15 apical cells in a usually slightly depressed apex, giving rise to lines of cells radiating to the branch margin. Structure of wing 1–8 cells thick (usually 2 or more), with the midrib 8–30 cells thick, differentiated in thicker blades into an outer cortex of densely phaeoplastic cells and an inner medulla of slightly larger, sparsely phaeoplastic cells. Phaeophycean hair tufts scattered or in lines, hairs originating from derivatives of cortical cells cut off as a patch or laterally from each cortical cell.

Reproduction: Unilocular sporangia scattered or clustered in sori, on both sides of the thallus, derived from the cortical cells and situated either within or external to the thallus surface, with or without a stalk cell; sporangia forming four spores. Sexual plants rare, with oogonia and antheridia in scattered sori.

Life history probably diplohaplontic and isomorphic in some species, direct from the sporophyte in other species.

Lectotype species: D. polypodioides (De Candolle) Lamouroux [= D. membranacea (Stackhouse) Batters].

Taxonomic notes: A genus of some 20 species, widespread in tropical and temperate waters, characterised by the much branched thalli with a distinct, percurrent, midrib.


LAMOUROUX, J.V.F. (1809a). Observations sur la Physiologie des Algues marines, et description de cinq nouveaux genres de cette famille. Nouv. Bull. Sci. Soc. Philom. Paris 1, 330–333, Plate 6 fig. 2.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
©Board of the Botanic Gardens and State Herbarium, Government of South Australia


1. Thallus with few to plentiful fine lateral veins running forwards from midrib to margin; sporangia in sori clumped around hair tufts which form lines curved downwards from midrib to margin

D. australis

1. Lateral veins absent; sporangia scattered over the thallus except for midrib (usually) and the margin


2. Thallus one cell thick except for the midrib

D. gracilis

2. Thallus 2–6 cells thick apart from midrib


3. Branching mainly proliferous from or near the midrib; hair tufts usually in reflexed lines from midrib to margin; sporangia densely covering thallus except for midrib and a well defined, often relatively broad, sterile margin

D. acrostichoides

3. Branching marginal, rarely proliferous; hair tufts scattered; sporangia scattered except usually for midrib and marginal edge


4. Thallus 1–2 (–3.5) cm broad, light brown; medulla mostly 2 cells thick apart from midrib

D. muelleri

4. Thallus 3–6 (–10) mm broad, dark brown; medulla mostly 4 cells thick apart from midrib

D. nigricans

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