| Cosmarium | 
|  | 
| Cosmarium botrytis | 
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| Scientific classification | 
| Kingdom: | Plantae | 
 
| Class: | Zygnematophyceae | 
 
| Order: | Desmidiales | 
 
| Family: | Desmidiaceae | 
 
| Genus: | Cosmarium Corda ex Ralfs
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| Type species | 
| Cosmarium undulatum 
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| Species | 
| C. angulosumC. auriculatumC. bioculatumC. bisphaericumC. blyttiiC. borgeseniiC. botrytisC. contractumC. costatumC. cucumisC. debaryiC. dentatumC. depressumC. dilatatumC. elegantissimumC. exiguumC. fontarabienseC. fontrabienseC. formosulumC. furcatospermumC. granatumC. hammeriC. humileC. impressulumC. isthmiumC. laeveC. levinotabileC. lundelliiC. norimbergenseC. obsoletumC. obtusatumC. ovaleC. pachydermumC. pseudoconnatumC. quadrumC. rectangulareC. reniformeC. sexangulareC. sp. ACKU 1232C. subcostatumC. subcucumisC. subprotumidumC. subtumidumC. succisumC. tenueC. tetragonumC. trilobulatumC. tumidumC. undulatum
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Cosmarium is a large genus of desmids (Desmidiaceae), a group of green algae closely related to the land plants (Embryophyta). Members of this genus are microscopic and found in freshwater habitats around the world.
The name Cosmarium comes from the Greek word κοσμάριον - kosmarion, meaning a small ornament.