Cosmarium tetragonum
Scientific classification Edit this classification
(unranked): Viridiplantae
(unranked): Charophyta
Class: Zygnematophyceae
Order: Desmidiales
Family: Desmidiaceae
Genus: Cosmarium
Species:
C. tetragonum
Binomial name
Cosmarium tetragonum
(Nägeli) W.Archer in Pritchard 1861[1]
Varieties

Cosmarium tetragonum var. elegans (Roy & Bisset) West & G.S.West 1908[2] (syn. C. elegans)

Synonyms

Euastrum tetragonum Nägeli

Cosmarium tetragonum is a species of green algae in the family Desmidiaceae. It is a freshwater species with a worldwide distribution.

Description

The nominate variety (var. tetragonum) is about 35 to 48 µm long, and 20 to 26 µm wide, 14 to 18 µm thick, with an isthmus about 6 to 12 µm long. Semicells are roughly rectangular in outline, with undulate margins; each side has about four bumps and the top side has about two bumps.[3]

Varieties

Cosmarium tetragonum is variable and several varieties have been described. They are:

  • Variety lundelii differs from the nominate variety that the lateral bumps are unequal; the two median bumps are larger.[3]
  • Variety bipapillatum also has two median bumps that are larger, but also has a protuberance right at the base of the semicell, near the isthmus.[3]
  • Variety ornatum has a crease that follows the margin of the cell; the crease may also have projections near the apex of the semicell.[3]
  • Variety intermedium has stout cells that are 1.5 times as long as broad; semicells are more trapezoidal.[3]

References

  1. ↑ Pritchard, A. (1861). A history of infusoria, including the Desmidiaceae and Diatomaceae, British and foreign. Fourth edition enlarged and revised by J. T. Arlidge, M.B., B.A. Lond.; W. Archer, Esq.; J. Ralfs, M.R.C.S.L. ; W. C. Williamson, Esq., F.R.S., and the author. pp. i-xii, 1- 968, 40 pls. London: Whittaker and Co., Ave Maria Lane. (description page 732)
  2. ↑ West, W. & West, G.S. (1908). A monograph of the British Desmidiaceae. III. pp. [i]-xv, [1]-274, pl. 65-95. London: The Ray Society. (description page 20)
  3. 1 2 3 4 5 Prescott, G. W.; Croasdale, H. T.; Vinyard, W. C.; Bicudo, C. E. M. (1981). A Synopsis of North American Desmids. Part II: Desmidiaceae: Placodermae. Section 3. Lincoln: University of Nebraska Press. p. 720. ISBN 9780835737920.
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