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Electronic Flora of South Australia Family Fact Sheet

Tribe HERPOSIPHONIEAE Schmitz & Falkenberg 1897: 457

Phylum Rhodophyta – Family Rhodomelaceae

Thallus completely to partially prostrate, often with erect or free upper parts. Branching exogenous, with defined sequences of indeterminate and determinate lateral branches, the determinate laterals simple or becoming slightly to regularly branched. Indeterminate axes compressed or subterete, bilaterally or radially developed, apices usually dorsiventrally developed, often curved upwards (dorsally), axes attached by rhizoids from ventral or lateral pericentral cells. Pericentral cells 4 to 16, not divided transversely, usually ecorticate (slightly corticate in Gredgaria). Trichoblasts usually present on determinate laterals, often rare.

Reproduction: Gametophytes dioecious, occasionally monoecious. Procarps borne on basal cells of trichoblasts, the fertile axial cells soon becoming polysiphonous. Carposporophytes with a basal fusion cell, branched gonimoblast and clavate terminal carposporangia. Cystocarps ovoid to urceolate, lateral on determinate laterals; pericarp ostiolate, usually ecorticate. Spermatangial organs ovoid to lanceoid, on trichoblasts, usually with sterile basal and apical cells.

Tetrasporangia in straight to curved determinate laterals, single per segment, in straight to slightly curved rows, with 2–3 cover cells.

Type genus: Herposiphonia Nägeli 1846: 238.

Taxonomic notes: The tribe includes some 9 genera, 7 on southern Australian coasts including 3 newly described below, distinguished by the defined but varied patterns of branching involving regular sequences of indeterminate and determinate laterals or of determinate lateral and branch initials only; the indeterminate laterals may remain only slightly developed or may grow into longer lateral axes, whereas the determinate ones usually remain short, simple or slightly branched. The branching patterns of the new genera are usually regular and ally them with other Herposiphonieae, such as Ditria and Womersleyella described by Hollenberg (1967a). The branching patterns of several genera have been analysed by Schneider & Walde (1992).

References:

HOLLENBERG, G.J. (1967a). New genera in the Rhodomelaceae from the Central Pacific. Bull. S. Calif. Acad. Sci. 66, 201–221.

NÄGELI, C. (1846). Herposiphonia. Zeitschr. für. wissensch. Botanik. 3, 4, 238–256.

SCHMITZ, F. & FALKENBERG, P. (1897). Rhodomelaceae. In Engler, A. & Prantl, K., Die natürlichen Pflanzenfamilien. T.1. Abt. 2, pp. 421–480. (Englemann: Leipzig.)

SCHNEIDER, C.W. & WALDE, R.E. (1992). L-system computer simulations of branching divergence in some dorsiventral members of the tribe Polysiphonieae (Rhodomelaceae, Rhodophyta). Phycologia 31, 581–590.

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

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

KEY TO GENERA OF HERPOSIPHONIEAE

1. Axes with 3 or 5–7 (–13) simple, determinate laterals between each indeterminate lateral

2

1. Axes with single or paired determinate laterals on alternate sides of the indeterminate axes

3

2. Axes with 3 simple determinate laterals between each indeterminate lateral

HERPOSIPHONIA

2. Axes with 5–7 (–13) simple determinate laterals between each indeterminate lateral

HERPOSIPHONIELLA

3. Prostrate axes with erect branches 1–3 cm high; successive axial segments with a long semi-determinate branch, a short indeterminate branch, and no branch on 1 (–3) segments

TIPARRARIA

3. Prostrate axes with distichously arranged and largely prostrate lateral branches; determinate laterals paired or single

4

4. Determinate laterals appearing paired from successive segments on alternate sides of axes

5

4. Determinate laterals single on alternate sides of axes

6

5. Determinate lateral pairs on successive segments of axes

DIPTEROSIPHONIA

5. Determinate lateral pairs usually separated by one segment with only a small cell cut off from the axial cell

DITRIA

6. Determinate laterals pinnately branched, each alternate pair separated by an axial segment with only a cell formed by division of a dorsal pericentral cell; cortication absent

HERPOPTEROS

6. Determinate laterals simple, becoming pinnate, separated by a single segment and with small clusters of corticating cells lying over the end walls of the pericentral cells, later spreading

GREDGARIA


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