Electronic Flora of South Australia Genus Fact Sheet

Genus JANIA Lamouroux 1812: 186

Phylum Rhodophyta – Class Florideophyceae – Order Corallinales – Family Corallinaceae – Subfamily Corallinoideae – Tribe Janieae

Thallus dichotomously branched (with limited development of pinnae in a few non-Australian species), adventitious branchlets rare; intergenicula cylindrical to compressed, unbranched or bearing two branches on broadened upper parts; holdfast small, crustose, or stoloniferous. Structure of a medulla of 1–20 (–25) tiers of cells per intergeniculum, cortex thin, of filaments of 1–3 cells arising from the outer medullary filaments, epithallial cells elongate, unistratose, with anterior trichocyte pores.

Reproduction: Conceptacles axial, usually swollen, pores central. Gametangial thalli usually dioecious, monoecious in some species. Female conceptacles bearing (1–) 2 (–4) branchlets, which sometimes consist of several intergenicula, fusion cells biconvex, 8–35 µm thick and 40–130 µm across, gonimoblast filaments marginal. Male conceptacles elongate, lacking branchlets, with spermatangial initials over the upper inner walls.

Tetrasporangial (and bisporangial) conceptacles bearing (1–) 2 (–4) branchlets, conceptacles sometimes in series, each containing up to 10 tetrasporangia, bisporangia or 3-celled sporangia.

Lectotype species: J. rubens (Linnaeus) Lamouroux 1816: 272 (Manza 1937: 47).

Taxonomic notes: The southern Australian species of Jania were monographed by Johansen & Womersley (1994).

Jania is characterised by its dichotomous branching with axial conceptacles.

References:

JOHANSEN, H.W. & WOMERSLEY, H.B.S. (1994). Jania (Corallinales, Rhodophyta) in southern Australia. Aust. Syst. Bot. 7, 605–625.

LAMOUROUX, J.V.F. (1812). Sur la classification des Polypiers coralligenès non entièrement pierreux. Nouv. Bull. Sci. Soc. Philom. Paris 3, 181–188.

LAMOUROUX, J.V.F. (1816). Histoire des Polypiers Coralligènes Flexibles. (Poisson: Caen.)

MANZA, A.V. (1937). The genera of articulated corallines. Proc. Nat. Acad. Sci. 23, 44–48,

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

Author: H.B.S. Womersley & H.W. Johansen

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 JANIA

1. Branches less than 200 µm in diameter, terete or almost so, intergenicula with 1–3 tiers of medullary cells	2
1. Lower branches usually more than 200 µm broad, terete or compressed, intergenicula with 4–20 (–25) tiers (indistinct in J. pusilla) of medullary cells	4
2. Intergenicula L/D 3–5; conceptacles containing bisporangia or gametangia	J. parva
2. Intergenicula L/D 1–3; conceptacles containing tetrasporangia, three-celled sporangia, or gametangia	3
3. Thallus 2–4 (–6) cm high, epiphytic on Fucales and seagrasses (rarely epilithic); intergenicula terete, (70–) 100–200 (–250) µm long, 120–200 (–250) µm in diameter below, tapering slightly above, LID 1–3 with 1 (–2) tiers of medullary cells; propagules unknown; conceptacles amphoroid (i.e. with branchlets from the upper shoulders); tetrasporangia with four spores	J. micrarthrodia
3. Thallus (1–) 2–6 (–10) mm high, epiphytic on seagrasses or Myriodesma; intergenicula terete to slightly compressed, (100–) 110–150 (–165) µm long, (40–) 60–100 (–120) µm in diameter, L/D 1.2–2 (–2.5); propagules common; conceptacles non-amphoroid (i.e. with branchlets from the lower sides); each tetrasporangium replaced by a large, two-nucleate central cell and small uninucleate basal and apical cells	J. minutes
4. Thallus branched in various planes, branches terete or subterete throughout, epilithic; 4–20 (–25) tiers of medullary cells per intergeniculum	J. verrucosa
4. Thallus complanately branched, with compressed intergenicula in lower parts, epilithic or epiphytic; usually 4–9 tiers (indistinct in J. pusilla) of medullary cells per intergeniculum	5
5. Thallus 2–5 (–10) mm high, 3–10 (–12) intergenicula long, upper intergenicula compressed, 200–600 (–800) µm broad, medullary tiers obscure; conceptacles embedded and inconspicuous; usually epiphytic on Cystophora	J. pusilla
5. Thallus 2–6 cm high, more than 20 intergenicula long, lower intergenicula only compressed and cheilosporoid, (200–) 400–1000 (–1250) µm broad, upper intergenicula terete and janioid, (80–) 100–250 (–300) µm in diameter with swollen conceptacles; 4–9 medullary tiers per intergeniculum; epiphytic on Sargassum or other algae (apparently not on Cystophora) or epilithic	6.1 pulchella

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