Electronic Flora of South Australia Genus Fact Sheet

Genus PHACELOCARPUS Endlicher & Diesing 1845: 289, nom. cons.

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Phacelocarpaceae

Thallus 10–50 cm high, much branched with irregular long and short branches bearing short, distichous (or tristichous), teeth-like ramuli, with a discoid holdfast. Structure uniaxial, with a conspicuous though small apical cell cutting off alternately four periaxial cells, in most species (alternately paired in P. alatus) the first developing into a filament and forming the ramuli, that opposite forming a filament which normally extends to the sinus between the ramuli, and the two transverse periaxial cells forming short clusters of cells which form the cortex on the flat surface of the rachis; in the ramuli, the lateral periaxial cells develop less extensively, and in terete ramuli all periaxial cells develop similarly. Abundant rhizoids, developed from the inner periaxial cells, surround the enlarged axial filament in the branches. Cortex pseudoparenchymatous, cells ovoid, decreasing in size outwardly, with some mid-cortical cells having refractive inclusions (gland-like) in some species.

Reproduction: Reproductive bodies usually formed as a result of continued growth of the lateral periaxial filament reaching the sinus between tumuli, forming a short shoot which becomes fertile; in P. complanatus however they are borne on the edge or surface of the ramuli and in P. tristichus on the rachis. Sexual thalli dioecious. Procarps usually bicarpogonial, cystocarps usually distinctly stalked, ovoid and bilabiate with an ostiolar slit, carposporophyte with a basal fusion cell, erect or spreading gonimoblast filaments each with 1–2 terminal carposporangia. Spermatangia in slits in sessile or stalked nemathecia.

Tetrasporangia in slits in sessile or globular, stalked, nemathecia, amongst sterile filaments, small, zonately divided.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Type species: P. tortuosus Endlicher & Diesing 1845: 290, from Port Natal, South Africa.

Taxonomic notes: A genus of 9 species, two from South Africa, 1 from East Africa and Madagascar, 5 from southern Australia (with 3 in New Zealand) and 1 from Japan.

References:

ENDLICHER, S.L. & DIESING, C.M. (1845). Algarum natalensium diagnoses. Bot. Zeit. 3, 288–290.

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.

KEY TO SPECIES OF PHACELOCARPUS

1. Ramuli usually shorter or about as long as width of rachis; spermatangial and tetrasporangial nemathecia stalked on the rachis or sessile on the ramuli

2

1. Ramuli distinctly longer than width of rachis; spermatangial and tetrasporangial nemathecia always on the rachis, stalked or sessile

3

2. Spermatangial and tetrasporangial nemathecia globular, stalked, on the edge of rachis between ramuli; rachis distinctly winged, with a prominent raised midrib; cortical gland cells conspicuous

P. alatus

2. Cystocarps, sessile or stalked, and spermatangial and tetrasporangial nemathecia sessile, all on upper face or edge of ramuli; rachis flattened but less distinctly winged; cortical gland cells absent

P. complanatus

3. Ramuli usually separated by 2–6 times their basal width; rachis more or less terete, mature ramuli terete and only slightly basally broader; spermatangial and tetrasporangial nemathecia globular or ovoid, sessile or almost so on the rachis between ramuli

P. sessilis

3. Ramuli usually separated by 0.5–1.5 times their basal width; rachis and ramuli usually compressed; spermatangial and tetrasporangial nemathecia stalked or sessile on the rachis

4

4. Mature branches (including ramuli) 1–2 (–2.5) mm across, lower rachis slender; spermatangial and tetrasporangial nemathecia sessile or almost so on rachis

P. apodus

4. Mature branches (including ramuli) (2–) 3–5 mm across, lower rachis robust; spermatangial and tetrasporangial nemathecia stalked

P. peperocarpos


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