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Tribe PTEROTHAMNIEAE Athanasiadis 1996: 44

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae

Thallus erect, 5–30 cm high, much branched with essentially complanate lateral branches, axial cells each with 2–4 whorl-branchlets which are of equal size or not (often as more-branched major ones and less-branched minor ones) and distichously, decussately, tristichously or irregularly branched; basal cells of whorl-branchlets laterally branched or not. Lateral branches arising from axial cells in place of a whorl-branchlet or from basal cells of whorl-branchlets. Lower axes corticate or not with loose rhizoids, arising from the basal cells of whorl-branchlets, and forming a basal rhizoidal holdfast. Structure. Apical cells usually small, young branches flexuous or straight. Whorl-branchlets with variously sized and shaped basal cells, upper branching usually relatively dense; gland cells usually present, or absent in some taxa. Cells uninucleate.

Reproduction: Gametophytes dioecious. Carpogonial branches borne on the basal cells of rachides of whorl-branchlets, usually on several successive axial cells near apices, with post-fertilization fusions between the axial, residual supporting, and lower gonimoblast cells common. Carposporophytes with several lobes and surrounded by involucral whorl-branchlets from the axial cell below. Spermatangia terminal on special branch clusters on lower cells of the whorl-bra nchlets or their pinnules.

Tetrasporangia on cells of the whorl-branchlets or on special branches, sessile or pedicellate, decussately divided.

Life History triphasic with isomorphic gametophytes and tetrasporophytes.

Taxonomic notes: This tribe was established by Athanasiadis with Pterothamnion as the only genus. Bahia is here provisionally added to the tribe, since the two genera are similar in habit, branching, carpogonial branch position and enveloping whorl-branchlets, and in spermatangial arrangement and in tetrasporangia. There are, however, clear cut differences between them (see key).

References:

ATHANASIADIS, A. (1996). Morphology and classification of the Ceramioideae (Rhodophyta) based on phylogenetic principles. Opera Botanica No. 128, pp. 1–216.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
©State Herbarium of South Australia, Government of South Australia

KEY TO GENERA OF PTEROTHAMNIEAE

1. Axial apices straight to flexuous, axial cells with 2 or 4 opposite whorl-branchlets; gland cells common to rare, occasionally absent, ovoid or conical at an angle to their bearing cell; tetrasporangia on cells of whorl-branchlets

PTEROTHAMNION

1. Axial apices usually not flexuous, axial cells with 2 or 3 whorl-branchlets; gland cells absent; auxiliary cells developing a chain of 3 or 4 cells, the second fusing with the fertilized carpogonium; tetrasporangia on special branch systems on cells of the whorl-branchlet rachides

BALLIA


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