Electronic Flora of South Australia Family Fact Sheet

FAMILY SCYTOSIPHONACEAE Farlow

Phylum Phaeophyta – Order Scytosiphonales

Thallus (gametophyte) terete or compressed to foliose, or subglobose to convolute or clathrate, solid or hollow, essentially unbranched, usually 2–30 cm high. Growth diffuse. Structure polystichous, with an inner medulla of larger, clear, cells, with or without internal rhizoids, and an outer cortex of small, phaeoplastic, cells, with phaeophycean hairs usually present. Alternate thallus discoid to crustose, haplostichous, pseudoparenchymatous.

Reproduction: Gametophytes bearing plurilocular organs in surface sori, producing zooids which develop directly or through filamentous or discoid stages, or which act as gametes under certain conditions. Discoid or crustose stages with unilocular sporangia.

Life history heteromorphic, diplohaplontic or direct.

Taxonomic notes: The other family of the order, the Chnoosporaceae Setchell & Gardner (1925, p. 552) differs from the Scytosiphonaceae in being subdichotomously branched and in having largely subapical growth.

The Scytosiphonaceae are well represented in southern Australia by several genera common in the mid to upper eulittoral zones. In summer the crustose stage is present, but care is needed to differentiate this stage from true members of the Ralfsiaceae. Ralfsia sub-genus Ralfsia has assurgent, curved, filaments arising from the basal layer and a multifilament margin, whereas sub-genus Stragularia has erect filaments developing behind the monostromatic basal margin; the latter corresponds to the crust of Scytosiphonaceae.

References:

SETCHELL, W.A. & GARDNER, N.L. (1925). The marine algae of the Pacific coast of North America. Part III. Melanophyceae. Univ. Calif Publ. Bot. 8, 383–898, Plates 34–107.

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

KEY TO ERECT PHASES OF GENERA OF SCYTOSIPHONACEAE

1. Thallus erect, terete to flattened, usually 3–20 times as high as broad

2

1. Thallus irregularly pulvinate to globular, hollow, 0.5–1.5 times as high as broad, with a continuous or perforated membrane

3

2. Thallus flattened, solid; sori without unicellular paraphyses; phaeophycean hairs rare to occasional

PETALONIA

2. Thallus terete to compressed, hollow or with the sides adjacent; sori with unicellular paraphyses; phaeophycean hairs abundant

SCYTOSIPHON

3. Thallus with a continuous, thin, membrane; sori with 1–3 celled paraphyses

COLPOMENIA

3. Thallus clathrate, with small to relatively large perforations in the membrane; sori without paraphyses

HYDROCLATHRUS


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