A class (in some classifications a division: Charophyta) of algae that in some ways resemble bryophytes (Bryophyta). They occur in fresh and brackish water and their calcified fructifications are ornamented with spiral striae. Neglected by geologists until 1959, they are now used as stratigraphic markers in Cenozoic strata. See gyrogonite.
Subjects: Earth Sciences and Geography.