Cell outline crescent-shaped (lunate) with green contents
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Cells are small, each containing a single chloroplast; although may associate into colonies, these are not mucilaginous.
Selenastrum -
Cells large and solitary, containing two chloroplasts separated by clear space in cell centre.
Closterium -
Cells small, usually associated in small colonies surrounded by mucilage (if found singly, difficult to distinguish from Selenastrum).
Kirchneriella