Electronic Flora of South Australia Genus Fact Sheet

Genus PEYSSONNELIA Decaisne 1841: 168

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Peyssonneliaceae

Thallus completely to largely prostrate, crustose and tightly adherent to loosely attached, thin to relatively thick, simple and rounded to much divided essentially in the one plane, often with concentric growth zones from the marginal thallus meristem, usually with a hypobasal layer of aragonite calcification between the rhizoids. Structure of a single basal layer of branched filaments, lying almost parallel or forming many flabellules, producing unicellular or multicellular rhizoids below and above with each cell cutting off centrally or anteriorly a single cell which forms two chains of assurgent to erect cells which may branch further and remain laterally coherent, or be relatively free, separating on squashing, and mucilaginous; internal calcification (cystoliths) often present in cells of erect filaments.

Reproduction: Sexual thalli monoecious or dioecious, gametangia in superficial nemathecia (usually with sterile paraphyses) on the upper surface. Carpogonial branches 3–6-celled, the fertilized carpogonium forming connecting filaments to auxiliary cells in adjacent to more remote auxiliary cell filaments, with the carposporophytes consisting largely of carposporangia in short rows. Spermatangia produced in dense clusters on cells of erect filaments.

Tetrasporangia in superficial nemathecia, usually terminal on the erect filaments and lying among slender multicellular paraphyses, cruciately divided.

Lectotype species: P. squamaria (S.G. Gmelin)Decaisne 1842: 360.

Taxonomic notes: Peyssonnelia is credited with over 40 species (see Denizot 1968) some of which are common in subtidal to deep-water situations; collections of tightly adherent species are not easily made and are often lacking in herbaria. Probably at least one or two further species exist in southern Australia apart from those described below, but adequate material is not available. Sexual plants are generally rare.

The structure and reproduction of the genus are reviewed by Maggs & Irvine (1983), but reproductive data on many species is lacking. Following Yoneshigue (1984), Cruoriella is considered not generically distinct from Peyssonnelia. If the former genus were recognised, P. boudouresquei would belong to it.


DECAISNE, J. (1841). Plantes de l'Arabie heureuse. Archs Mus. natn. Hist. nat., Paris 2, 89–199, Plates 5–7.

DECAISNE, J. (1842). Essais sur une classification des Algues et des Polypiers calcifères de Lamouroux. Ann. Sci. Nat., 2 Sér. Bot., 17, 297–380, Plates 14–17.

DENIZOT, M. (1968). Les Algues Floridées encroûtantes (a l'exclusion des Corallinacées). (Paris.)

MAGGS, C.A. & IRVINE, L.M. (1983). Peyssonnelia immersa sp. nov. (Cryptonemiales, Rhodophyta) from the British Isles and France, with a survey of infragenic classification. Br. phycol. J. 18, 219–238.

YONESHIGUE, Y. (1984). Flore marine de la region de Cabo Frio (Brésil). 4. Sur une espèce nouvelle du genre Peyssonnelia (Cryptonemiales: Rhodophyta). Vie Milieu 34, 133–137.

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

Author: 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.


1. Hypothallial cells in RVS L/D (2–) 3–4, with the basal cell of assurgent filaments arising at < 50° to the hypothallial layer, connected to the distal end of the hypothallial cells; rhizoids multicellular


1. Hypothallial cells in RVS L/D 1–2, pit-connected centrally to the basal cell of erect filaments arising at > 55° to the hypothallial layer; rhizoids unicellular


2. Thallus orbicular to lobed with broad margins, mostly to partly adherent, with clusters of ovoid calcified cells (cystoliths) in the mid (to upper) thallus; hypobasal cells producing rhizoids, angled forward through the thallus sheath, usually bent on emergence and with the basal part within the sheath

P. capensis

2. Thallus divided or lobed, largely free from substrate and often slightly erect; internal calcification absent or confined to isolated cells; rhizoids more or less at right angles to hypothallial cells, hypobasal cells absent


3. Thallus medium to dark red, (2–) 5–15 cm long or broad, becoming much branched with most branches 5–15 mm broad, irregular in width; assurgent filaments 15–20 cells long with some sideways-growing filaments present; calcification within thallus absent, hypobasal calcification prominent; tetrasporangial nemathecia prominent, tetrasporangia 160–200 µm long and 95–130 µm in diameter

P. novae-hollandiae

4. Thallus completely adherent to rock or shells, with few, short, rhizoids; vegetative thallus 120–400 µm thick, with erect filaments 11–30 cells long, firmly united or relatively free and mucilaginous; tetrasporangial nemathecia low


4. Thallus completely adherent to slightly or largely free from substrate, rhizoids frequent; vegetative thallus (60–) 80–120 (–160) µm thick, erect filaments 3–8 (–12) cells long; tetrasporangial nemathecia raised


160. –400 µm thick, erect filaments 15–30 cells long, firmly united laterally

P. splendens

120. –320 µm thick, erect filaments 11–18 cells long, easily separable and mucilaginous

P. boudouresquei

6. Basal layer filaments forming small flabellules as seen from below, thallus completely adherent

P. dubyi

6. Basal layer filaments more or less parallel as seen from below; thallus incompletely adherent, free at least marginally

P. inamoena

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