British distribution (genus): Widespread, freshwater.
A colonial, motile, green alga, in which several hundred to several thousand biflagellated cells are embedded in mucilage in a hollow sphere, the entire colonies often more than a millimetre in diameter and easily visible to the naked eye. The cells are usually connected by protoplasmic strands.
Mostly in eutrophic waters, in plankton and sometimes forming dense blooms colouring the water green.
Photograph of material in culture, 1998, species unnamed.