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Electronic Flora of South Australia Genus Fact Sheet

Genus INVOLUCRANA Baldock & Womersley 1968: 214

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Sphondylothamnieae

Thallus erect, much branched with irregular long axes bearing first one then a second whorl-branchlet, largely distichously, on each axial cell, with some cells producing a third (rarely a fourth); indeterminate laterals developing from the first formed whorl-branchlet; whorl-branchlets relatively slightly branched; cortication of older axes by descending anastomosing rhizoids from the basal cells of whorl-branchlets. Cells relatively large, multinucleate.

Reproduction: Gametophytes dioecious. Procarpic with 3-celled fertile axes arising laterally on the subterminal cell of whorl-branchlets; subapical cells with 2 pericentral cells, one of which functions as the supporting cell and cuts off a sterile cell; carposporophyte with a central, lobed, fusion cell bearing branches with terminal clavate carposporangia, surrounded by an inner involucre of 3 branchlets arising from the apical cell of the fertile axis, the sterile pericentral cell and the sterile cell on the supporting cell; an outer involucre develops from the lower whorl-branchlets. Spermatangia borne on ovoid heads on reduced branch systems on lower cells of whorl-branchlets.

Polysporangia, with 20–32 spores, are borne terminally or laterally on lower cells of reduced branch systems on the lower cells of whorl-branchlets.

Type species: I. meredithiana (J. Agardh) Baldock & Womersley 1968: 215. A genus of two species on southern Australian coasts.


BALDOCK, R.N. & WOMERSLEY, H.B.S. (1968). The genus Bornetia (Rhodophyta, Ceramiaceae) and its southern Australian representatives, with a description of Involucrana gen. nov. Aust. J. Bot. 16, 197–216, Plates 1–4.

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

Author: 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


1. Thallus branching irregular, subdistichous; whorl-branchlets often indistinct from indeterminate branches, 2–3 (–4) per axial cell, radial on main axes, 5–20 mm long, median cells 2–4 mm long

I. meredithiana

1. Thallus branching mostly distichous; whorl-branchlets nearly always distinct from indeterminate branches, distichous on main axes, 2 (–4) per axial cell, 2.5–4 mm long, median cells 0.7–1.2 mm long

I. crassa

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