153,789 species and infraspecific names are in the database, 21,012 images, 59,564 bibliographic items, 413,155 distributional records.

Penium Brébisson ex Ralfs, 1848

Classification:
Empire Eukaryota
Kingdom Plantae
Subkingdom Viridiplantae
Infrakingdom Streptophyta infrakingdom
Phylum Charophyta
Class Conjugatophyceae (Zygnematophyceae)
Order Desmidiales
Family Peniaceae

Lectotype species: Penium margaritaceum Brébisson

Original publication:Ralfs, J. (1848). The British Desmidieae. pp. [i]-xxii, [i], [1]-226, pls I-XXXV. London: Reeve, Benham & Reeve.
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Type designated in Guiry, M.D. (2013). Taxonomy and nomenclature of the Conjugatophyceae (=Zygnematophyceae). Algae. An International Journal of Algal Research 28: 1-29.
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Taxonomic status: currently recognized as a distinct genus.

Most recent taxonomic treatment adopted: Brook, A.J. & Johnson, L.R. (2002). Order Zygnematales. In: The Freshwater Algal Flora of the British Isles. An identification guide to freshwater and terrestrial algae. (John, D.M., Whitton, B.A. & Brook, A.J. Eds), pp. 479-593. Cambridge: Cambridge University Press.

Description: Cells solitary, short-cylindric to elongate-cylindric (length 19-450 um; length 2-35 times width), straight, with broadly rounded or truncate ends; shallow median constriction sometimes present. Cell wall with or without girdle bands, smooth or with striae, pores, granules or spines. Ultrastructurally cell wall two layered, with perforated outer layer and continuous inner layer. Cell wall sometimes brown, often with different wall sections different shades of brown. Two (rarely four) chloroplasts per cell, axial and stellate in end view (spiralling parietal bands in one species) with 1-2 axial pyrenoids. Terminal vacuoles with small crystals in some species. Nucleus at middle between chloroplasts. Asexual reproduction by transverse cell division. Some species divide only at median suture and produce new semicell on each daughter cell. Other species from girdle band on new semicell. Sexual reproduction by conjugation. Gametangia come together within mucilage envelope;. gametes fuse between gametangial. Zygospores single or paired, spherical to ellipsoid (occasionally angular), usually smooth walled. Mesopore wall of P. silvae-nigrae corrugated or finely punctate. Penium cosmopolitan; usually in acidic, oligotrophic ponds or lakes or in Sphagnum bogs. Emend. Kouwets & Coesel 1984: 561.

Information contributed by: J.F. Gerrath. The most recent alteration to this page was made on 12 Sep 2013 by M.D. Guiry.

Numbers of names and species: There are 97 species names in the database at present, as well as 119 infraspecific names. Of the species names, 41 have been flagged as accepted taxonomically on the basis of the listed literature under the species name. In some instances, opinions on taxonomic validity differ from author to author and users are encouraged to form their own opinion. AlgaeBase is a work in progress and should not be regarded as a definitive source only as a guide to the literature..

Names: ('C' indicates a name that is accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):

Click here to also show infraspecific names in the list below.

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Users are responsible for verifying the accuracy of information before use, as noted on the website Content page.

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.

Created: 11 April 2002 by M.D. Guiry

Verified by: 12 September 2013 by M.D. Guiry

Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=43539

Citing AlgaeBase
Please cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 10 December 2018.

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