Electronic Flora of South Australia Genus Fact Sheet

Genus HENNEDYA Harvey 1855a: 552

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Acrotylaceae

Thallus erect, subdichotomously and laterally branched, largely complanately, branches flat, 2–10 mm broad, becoming stalked below; holdfast discoid-conical. Structure

multiaxial, with a filamentous medulla and pseudoparenchymatous cortex with a layer of large, isodiametric inner cortical cells on each side and an outer cortex of small cells.

Reproduction: Sexual thalli monoecious; procarpic; monocarpogonial. Carpogonial branches on outermost medullary cells, 2-celled, inwardly directed with reflexed trichogynes. Supporting cell acting as auxiliary cell. Gonimoblast initials several, largely inwards, with nutritive cells produced by adjacent vegetative cells forming a sheath and the gonimoblast filaments spreading around a cavity formed by breakdown of the diploidized auxiliary cell, becoming centripetal with terminal carposporangia. Cystocarps largely protuberant, with filamentous enveloping tissue, and a cortical ostiole. Spermatangia in scattered, sunken, urceolate clusters.

Tetrasporangia scattered in the outer cortex, laterally to basally pit-connected, zonately divided.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Type (and only) species: H. crispa Harvey 1855a: 552.

Taxonomic notes: Hennedya differs from Acrotylus in its broader thallus, the two distinctive layers of large inner cortical cells, and reproductively in being monocarpogonial with protruding cystocarps, and having scattered tetrasporangia (not in nemathecia).

References:

HARVEY, W.H. (1855a). Some account of the marine botany of the colony of Western Australia. Trans. R. Ir. Acad. 22, 525–566.

The Marine Benthic Flora of Southern Australia Part IIIA complete list of references.

Author: G.T. Kraft & H.B.S. Womersley

Publication: Womersley, H.B.S. (14 January, 1994)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIA, Bangiophyceae and Florideophyceae (to Gigartinales)
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIA 1994, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.


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