Scientific name: Charophyceae
English name: Charopida
Vietnamese name: Tảo vòng
Other name:

The Charopida are a class of green algae, including the closest relatives of the embryophyte plants. Because they exclude the embryophytes, they make a paraphyletic group (though they are occasionally restricted to simply the Charales or stoneworts, which are monophyletic). In some groups, such as conjugating green algae, flagellate cells do not occur. The latter group does engage in sexual reproduction, and motility does not involve flagella, since they are totally lacking. Flagellate cells in the form of sperm are found in stoneworts (Charales) and Coleochaetales.