Freshwater Algae of North America Zygnematophyceae C.Hoek, D.G.Mann & H.M. Jahns (1995), nom. inval. - conjugating green algae see Class Zygnematophyceae Round ex Guiry (2013) Desmidiales - placoderm desmids 1 Closteriaceae A. Pritch. (1872) 2 Desmidiaceae Kützing ex Ralfs (1845) 3 Gonatozygaceae 4 Peniaceae Haeckel (1894) [paraphyletic]