Hallasia Rosenvinge, 1924

Holotype species: Zygnema reticulatum Hallas

Original publication and holotype designation: Rosenvinge, L.K. (1924). Note sur le Zygnema reticulatum E. Hallas. Revue Algologique 1: 209-212.

Description: Thalli unbranched, forming extensive skeins of intertwining uniseriate filaments. Cells cylindrical, 18-20 um in diameter, from two to ten times longer than wide; cell wall two-layered with inner cellulose, outer mucilage layer; endwalls plane; no flagellated stages. Cells uninucleate; chloroplasts two per cell, axial in position, stellate in shape as in Zygnema; number increases up to seven during aplanospore formation. Sexual reproduction not observed. As aplanospores form, cells elongate, contents contract and pectic transparent gel accumulates, as occurs in Zygnemopsis during sexual zygospore formation. Aplanospores ellipsoid; upon germination produce one, two, or three germlings. Vegetatively similar to Zygnema; H. reticulata originally described as Zygnema reticulatum. Trait of multiple germlings from asexual spore has been considered analogous to pair of germlings (gones) produced from parthenospores in Cosmarium of related family Desmidiaceae. Because of vegetative similarity to Zygnema and Zygnemopsis, multiple germlings, and pectic gel in aplanospores the genus is included in Zygnematales. Nevertheless, taxonomic placement ambiguous in absence of conjugation; suggestion has been made to place in Zygnemopsis. Poorly known monotypic genus collected but once in Denmark.

Information kindly contributed by R.W. Hoshaw and R.M. McCourt but may now be outdated.

Taxonomic status: The taxonomic or nomenclatural status (or both) of this entity is in some way unresolved and requires further investigation.

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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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in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.

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Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 10 August 2011. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 22 December 2024