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Electronic Flora of South Australia Genus Fact Sheet

Genus ECHINOTHAMNION Kylin 1956: 506.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Polysiphonieae

Thallus erect, loosely to densely branched, with few and irregular, or numerous, radial indeterminate laterals bearing short, branched, determinate laterals; holdfast fibrous. Axes and main laterals soon becoming heavily corticated, determinate laterals ecorticate. Structure. Apical cells dome-shaped, subapical cells cutting off 4 pericentral cells which soon become corticated on indeterminate branches but remain conspicuous in transverse section; ecorticate determinate laterals produced spirally from close to apices. Determinate laterals first simple, soon branched from near their base, with trichoblasts mainly on their branches, soon caducous.

Reproduction: Gametophytes dioecious. Carposporophytes with a basal fusion cell and branched gonimoblast with clavate terminal carposporangia. Cystocarps sessile, slightly urceolate; pericarp ostiolate, 2 cells thick, ecorticate. Spermatangial branches replacing whole trichoblasts or as a basal branch, with sterile basal cells but usually no sterile apical cells.

Tetrasporangia in branches of determinate laterals, single per segment, spirally arranged.

Type species: E. hystrix (Hooker & Harvey) Kylin 1956: 506.

Taxonomic notes: A genus of 3 or 4 species, characterised by the densely corticated main branches bearing short determinate tufts of basally branched ecorticate ramuli with 4 pericentral cells.

Echinothamnion mallardiae (Harvey) Kylin is based on two Colenso 227 type specimens from the East coast of New Zealand, in TCD. On these specimens, "mallardiae" is crossed out and "lyalli" is written over it. The first specimens Harvey ascribed to P. mallardiae (Hooker & Harvey 1845b, footnote pp. 533, 534) were ones of Mrs Mallard from Port Phillip, Victoria, and since then "mallardiae" has been a commonly used name for southern Australian specimens, all of which have 4 pericentral cells whereas the New Zealand species has 5 and is doubtfully an Echinothamnion. The variable but distinctive southern Australian species is here included in E. hookeri since there is no clear difference between this species and what has been referred to as "mallardiae".


HOOKER, J.D. & HARVEY, W.H. (1845b). Algae Novae Zelandiae. Lund. J. Bot. 4, 521–551.

KYLIN, H. (1956). Die Gattungen der Rhodophyceen. (Gleerups: Lund.)

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

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. Indeterminate branching irregular with long, simple or little-branched laterals of various lengths

E. hystrix

1. Indeterminate branching radial with laterals for 4 or 5 orders, gradually decreasing in length from the thallus base upwards

E. hookeri

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