Electronic Flora of South Australia Genus Fact Sheet

Genus SEMNOCARPA Huisman, Foard & Kraft 1993: 145

Phylum Rhodophyta – Class Florideophyceae – Order Rhodymeniales – Family Lomentariaceae

Thallus erect, usually with percurrent axes bearing irregularly radial branches for 1–3 orders; branches terete to slightly compressed, hollow, basally constricted with solid partitions; holdfast discoid. Structure multiaxial, with a cluster of apical cells, developing a cortex of a single layer of larger cells and an outer cortex 1–2 cells thick of small cells and a medulla of irregular slender filaments bearing secretory cells; constrictions pseudoparenchymatous.

Reproduction: Gametangial thalli dioecious. Carpogonial branches 3-celled, borne on inner cortical (supporting) cells together with a 2-celled auxiliary cell branch. Carposporophytes with partially fused basal cells and all gonimoblast cells forming carposporangia. Cystocarp immersed, with the carposporophyte surrounded by an involucre of erect filaments derived from inner cortical cells, and the outer cortical cells branching to surround the ostiole. Spermatangia in sori near branch apices, cut off via initials from outer cortical cells.

Tetrasporangia in depressed sori, cut off laterally from outer cortical cells, tetrahedrally divided.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Type species: S. corynephora (J. Agardh) Huisman, Foard & Kraft 1993: 146.

Taxonomic notes: A genus of two species, the type and S. minuta Huisman, Foard & Kraft, both from southern Australia and south-western Western Australia.

Semnocarpa differs from Lomentaria in having immersed carposporophytes surrounded by an involucre of erect filaments, compared to the protruding cystocarps with a cortical pericarp in the latter.

References: The Marine Benthic Flora of Southern Australia Part IIIB

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (28 June, 1996)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIB. Gracilarialse, Rhodymeniales, Corallinales and Bonnemaisoniales
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIB 1996, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

KEY TO SPECIES OF SEMNOCARPA

1. Thallus 4–20 cm high, much branched with percurrent axes and irregular laterals of 2–3 orders	S. corynephora
1. Thallus 0.1–3 cm high, simple to branched with axes bearing short clavate laterals	S. minuta

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