Isoetes, commonly known as the
quillworts, is a genus of plants in the class
Isoetopsida and order
Isoetales. They are
lycopods. There are about 140–150 species, with a
cosmopolitan distribution but often scarce to rare. Some
botanists split the genus, separating two South American species into the genus
Stylites, although molecular data place these species among other species of
Isoetes, so the genus does not warrant taxonomic recognition.