Unicellular or filamentous green algae. The Zygnematophyceae includes some familiar green algae such as Spirogyra and Closterium. They are common in fresh water, but some species are terrestrial. Some species such as Spirogyra form bloom and are noticable in lakes or ponds. Closterium is sometimes used for laboratory.

The cell wall is cellulosic (but smaller than that of land plants) and sometimes includes polyphenols. The cellulose is synthesized by rosette terminal complexes in plasma membrane. The cell is sometimes surrounded a mucilage (pectin and hemicellulose). The cell sometimes glide on substrate by secretion of mucilage. The shape of chloroplast is varied, such as spiral, plate-like, stelllate etc. THe zygnematophycean algae never producec flagella nor centriole through life cycle. Mitosis is semi-closed and shows persistent tellophase spindle. Cytokinesis involves simple furrowing and (sometimes) cell plate with phragmoplast. There is no plasmodesmata. Asexual reproduction by means of fragmentation, binary fission or akinete. Sexual reproduction takes place by the characteristic process, conjugation. Zygote covered by cell wall containing sporopollenin-like material is resting stage.

The zygnematophycean algae was traditionally divided into the Zygnemataceae, Mesotaeniaceae and Desmidiaceae. However, former two taxa are polyphyletic.