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
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^ 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)
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^ 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)
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^ a b c d e 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.
