Placophora J.Agardh, 1863

Holotype species: Placophora binderi (J.Agardh) J.Agardh

Original publication and holotype designation: Agardh, J.G. (1863). Species genera et ordines algarum, seu descriptiones succinctae specierum, generum et ordinum, quibus algarum regnum constituitur. Volumen secundum: algas florideas complectens. Part 2, fasc. 3. pp. 787-1138, 1158-1291. Lundae [Lund]: C.W.K. Gleerup. [in Latin]

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Description: Prostrate. dorisiventral, lobed blades formed by congenital fusion of polysiphonous filaments. Original germling is a cylindrical erect branch, determinate, and producing proximal adventitious branches that form the prostrate system according to Scagel (1953). Five pericentral cells, 3 dorsal and 2 ventral; axial row of cells forming indistinct veins. Every segment produces a branch, produces in pairs alternating on either side of axis. Trichoblasts not present on prostrate thallus but rhizoids commonly cut off by ventral pericentral cells, thigmotrophic rhizoid tip may become multicellular (Scagel 1953). Erect cylindrical, exogenously or adventitiously developed polysiphonous branches may form on the thallus surface. Some of these become reproductive branches. Reproductive branches formed on erect, radially symmetrical branches that retain some degree of dorsiventrality (Scagel 1953). Female branches may produce trichoblasts on the dorsal side of most every segment. Fertile female trichoblasts proximally polysiphonous, 5 proximal pericentrals but up to 7 distally on the same branch, dorsal in P. binderi but spirally arranged in P. eckloniae. Usually only 1 spheroidal to urceolate cystocarp develops per fertile branch. Male capitula coniform, produced in place of trichoblasts in a longitudinal row on dorsal side of branch with only 5 pericentrals; in P. eckloniae, male capitula are in a spiral on the axis and up to 9 pericentrals may be present; a sterile tip usually present. Tetrasporangia formed in distal part of erect branches, 1 per segment in a dorsal straight series. Erect branchlet with 5 pericentrals in proximal segments but up to 9 in more distal regions. Two cover cells formed.

Information contributed by: R.E. Norris. The most recent alteration to this page was made on 2010-10-07 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Most recent taxonomic treatment adopted: Schneider, C.W. & Wynne, M.J. (2007). A synoptic review of the classification of red algal genera a half a century after Kylin's "Die Gattungen der Rhodophyceen". Botanica Marina 50: 197-249.

Comments: Epiphytic, usually on Codium (P. binderi) or Ecklonia (P. eckloniae) in temperate to subtropical South Africa, Australia, Japan, Tristan da Cunha and possibly Indonesia, although early recorded in Peru its presence there refuted by Dawson et al. (1964).

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Contributors
Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=35821

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 07 October 2010. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 22 November 2024