Electronic Flora of South Australia Genus Fact Sheet

Genus NEMACYSTIS Derbés & Solier 1850: 269

Phylum Phaeophyta – Order Chordariales – Family Spermatochnaceae

Thallus irregularly subdichotomous or laterally branched, haplostichous, slender, 5–30 cm long, 0.5–1 mm in diameter, cylindrical or tapering slightly, usually epiphytic. Branch apices with a single filament with apical growth. Medulla of the single axial filament. Cortex 2–5 cells thick, pseudoparenchymatous with smaller cells outwardly, developed from basal cells of the primary assimilatory filaments and usually with hyphal filaments on the surface. Primary assimilatory filaments formed close to branch apices and from virtually all outer cortical or hyphal cells, 8–20 cells long with apical or intercalary divisions, forming a well-developed layer of filaments over the whole thallus but often denuded below. Tufts of secondary assimilatory filaments not formed. Phaeophycean hairs developed from outer cortical cells or basal cells of the assimilatory filaments.

Reproduction: Reproduction by uniseriate, plurilocular sporangia producing zooids forming plethysmothalli (Sauvageau 1931, p.132) and by unilocular sporangia, formed at the base of the assimilatory filaments, producing dioecious gametophytes with isogametes (in N. decipiens — Peters & Müller 1986b).

Life history probably diplohaplontic and heteromorphic.

Type species: N. ramulosus Derbés & Solier.

Taxonomic notes: A genus of some 8 species (Kylin 1940, pp. 46–49), characterised by the single axial filament, with apical growth, and the continuous layer of long primary assimilatory filaments.


DERBÉS, A. & SOLIER, A.J.J. (1850). Sur les organes reproducteurs des Algues. Ann. Sci. nat. (Bot.), Ser. 3, 14, 261–282, Plates 32–37.

KYLIN, H. (1940). Die Phaeophyceenordnung Chordariales. Acta Univ. lund. N.F. Avd. 2, 36(9), 1–67, Plates 1–8.

PETERS, A.F. & MÜLLER, D.G. (1986b). Critical re-examination of sexual reproduction in Tinocladia crassa, Nemacystis decipiens and Sphaerotrichia divaricata (Phaeophyceae, Chordariales). Jap. J. Phycol. 34, 69–73.

SAUVAGEAU, C. (1931). Sur quelques Algues phéosporées de la rade de Villefranche (Alpes-Maritimes). Bull. Stn biol. Arcachon 28, 7–168.

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
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