Electronic Flora of South Australia Genus Fact Sheet

Genus ADENOCYSTIS Hooker & Harvey in Harvey & Hooker 1845: 179

Phylum Phaeophyta – Order Chordariales – Family Scytothamnaceae

Thallus of several simple, clavate to pyriform vesicles from a small, discoid holdfast, becoming 2–10 cm long and 0.5–3 cm in diameter. Structure multiaxial and haplostichous, differentiating into a pseudoparenchymatous cortex and loosely filamentous medulla which becomes filled with mucilage; surface of thallus with numerous, hair-bearing, scattered cryptostomata. Growth apical and peripheral, with an apical pit containing a tuft of phaeophycean hairs developed from basal cells which produce posteriorly cells which elongate to form the medullary filaments; filaments around the apical pit and nearby divide apically and periclinally to form the cortex, with the outer cells dividing obliquely to form anticlinal filaments.

Phaeoplasts discoid, with a pyrenoid. Phaeophycean hairs clustered, in cryptostomata.

Reproduction: Reproduction of the macrothallus (sporophyte) by unilocular sporangia formed amongst cortical filaments in vague and usually extensive surface sori. Gametophytes by plurilocular gametangia or from disc cells, producing isogametes.

Life history diplohaplontic and heteromorphic, with a filamentous or discoid gametophytic microthallus with occasional longitudinal cell divisions (Müller 1984).

Type species: A. lessonii (Bory) Hooker & Harvey [=A. utricularis (Bory) Skottsberg].

Taxonomic notes: The monospecific genus Adenocystis has usually been placed in the Dictyosiphonales, though Harvey (1858, p1.48) proposed that it be removed from the Laminariales (where J. Agardh had placed it) to the Chordariales. Recently Delépine & Asensi (1978, p.153) and Clayton (1985, p.288) have shown that the structure of the sporophyte thallus is haplostichous, and the former suggest that it is better placed in the Chordariales. Basing classification on the structure of the macrothallus (sporophyte), rather than the microthallus (gametophyte) which does show some longitudinal cell division in older parts (Müller 1984, p.89), Adenocystis seems to be most related to Scytothamnus and is provisionally placed in the Scytothamnaceae within the Chordariales. However, the difference in the phaeoplasts (Scytothamnus stellate, discoid in inner cells, and Adenocystis discoid) may need further consideration.

References:

CLAYTON, M.N. (1985). A critical investigation of the vegetative anatomy, growth and taxonomic affinities of Adenocystis, Scytothamnus and Splachnidium (Phaeophyta). Br. phycol. 1 20, 285–296.

DELÉPINE, R. & ASENSI, A. (1978). Réactions écophysiologiques et variations morphogénétiques chez Adenocystis et Utriculidium (Phéophycées). Rev. Algol., N.S., 13, 43–85.

HARVEY, W.H. & HOOKER, J.D. (1845). The Botany of the Antarctic Voyage of H.M. Discovery Ships Erebus and Terror in the years 1839–1843. I. Flora Antarctica. Part I. Algae, pp. 175–193, Plates 69–78.

HARVEY, W.H. (1858). Phycologia Australica. Vol. I, Plates 1–60. (Reeve: London.)

MÜLLER, D.G. (1984). Culture studies on the life history of Adenocystis utricularis (Phaeo- . phyceae, Dictyosiphonales). Phycologia 23, 87–94.

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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