desmids

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desmids A group of green algae (division Chlorophyta) which are basically unicellular but have two distinct halves, or ‘semicells’. The cells are usually solitary but in a few species they may form irregular or filamentous colonies. The cells may vary in shape within a single species, making identification and classification difficult. Sexual reproduction occurs by conjugation, similar to that in Spirogyra. They are found mainly in freshwater habitats and are usually indicators of clean (unpolluted) water.

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