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Electronic Flora of South Australia Genus Fact Sheet
Phylum Rhodophyta – Family Delesseriaceae
Thallus complanately and subdichotomously branched, with a subdichotomous midrib and straight to strongly crisped margins, with proliferous bladelets arising from the midrib. Holdfast discoid, usually epiphytic. Structure. Apical cells segmenting to an axial filament, and 2 lateral and later 2 transverse pericentral cells, with the lateral pericentral cells forming second-order rows of which some but not all cells form third-order rows, with nearly all rows reaching the blade margins; the subdichotomies arise by continued growth of a third-order row, just below the apex, to form a new apex and blade. Blades monostromatic, but cortication of midribs and adjacent wings of older blades occurs by slender rhizoidal filaments.
Reproduction: Reproductive structures borne mostly on ovate bladelets endogenous and proliferous from central axial cells of the midrib, but also on the subdichotomous blades.
Gametophytes dioecious. Procarps borne on transverse pericentral cells on both sides of blades, with the supporting cell bearing 2 carpogonial branches and one sterile group. Carposporophytes with a basal, branched, fusion cell and short terminal chains of carposporangia. Cystocarps sunken, situated on the midrib of blades, ostiolate with a pericarp 2–3 cells thick. Spermatangial sori on blades or bladelets, on either side of the sterile midrib, with cortical initials cutting off elongate spermatangia.
Tetrasporangial sori mainly on the bladelets, ovate, with 2 layers of tetrasporangia cut off from cortical initials and with outer small cortical cells.
Type (and only) species: D. crispatulum (Harvey) Millar & Huisman 1996b: 128.
Taxonomic notes: Dicroglossum is characterised by the exogenous marginal and subdichotomous branching of the thallus, plus endogenous production of bladelets which become reproductive, and also by the formation of 2 carpogonial branches on each supporting cell. It was placed in its own tribe (group) by Millar & Huisman. The subdichotomous branching originates by a third-order cell row near the apex developing into a new lateral branch (see Millar & Huisman 1996, fig. 12).
References:
MILLAR, A.J.K. & HUISMAN, J.M. (1996b). Dicroglossum crispatulum gen. et comb. nov. from Western Australia, representing a new tribe within the Delesseriaceae (Rhodophyta). J. Phycol. 32, 127–137.
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.
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