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Order Nemaliales

Family Galaxauraceae (see Huisman et al., 2004)

Dichotomaria Lamarck 1816:145 (amended by Huisman et al. 2004 and Wang & Liu 2005).

Holdfast discoid, formed of compact rhizoidal mass; axes terete or flattened, pseudo-dichotomously branched, with or without distinct segments; primary growth from meristematic cells at centre of rounded spices; medulla filamentous; life-history triphasic with gametophytes and tetrasporophytes isomorphic in appearance but different in cortical anatomy; cortex of gametophyte usually with 3 layers, inner 1-2 of large clear cells, outer of smaller pigmented cells; cortex of tetrasporophyte with 3-6 layers, inner 1-3 of large clear cells, outer borne on pigmented stalk cells. Spermatangia borne in sunken cavities. Mature cystocarp hemispherical, immersed in cortex/medulla, with ostiole and persistent pericarp. Tetrasporangia cruciately divided, solitary or in sori on surface of thallus, tetrasporangia borne laterally on stalk cells of epidermal cells or terminally on epidermal cells. Twenty two species are currently recognised (W. Guiry in Guiry & Guiry 2015), of which three are found on the South African south coast.

 

Key to Dichotomaria species

1 a. Axes strap-shaped, not jointed

D. diesingiana

1 b. Axes terete or compressed, jointed

2

2 a. Axes terete, marked constrictions between joints

D. obtusata

2 b. Axes compressed, usually not constricted at joints

D. tenera

 

References Dichotomaria

Guiry in Guiry, M.D. & Guiry, G.M. 2015. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 03 March 2015.

Huisman, J. M., Harper J. T. & G. W. Saunders 2004. Phylogenetic study of the Nemaliales (Rhodophyta) based on large-subunit ribosomal DNA sequence supports segregation of the Scinaiaceae fam, nov. and resurrection of Dichotomaria Lamarck Phycological Research 52(3): 224-234.

Lamarck J. B. 1816. Histoire naturelle des animaux sans vertèbres. Vol. 2. Déterville, Paris, 568 pp.

Wang, W.-L., & S.-M. Liu 2005. Systematics of the calcified genera of the Galaxauraceae (Nemaliales, Rhodophyta) with an emphasis on Taiwan species. Journal of Phycology 41: 685-703.

 

Cite this record as:

Anderson RJ, Stegenga H, Bolton JJ. 2016. Seaweeds of the South African South Coast.
World Wide Web electronic publication, University of Cape Town, http://southafrseaweeds.uct.ac.za; Accessed on 21 November 2018.