Quillwort

Quillworts are plants of the genus Isoëtes and Stylites, in the family Isoëtaceae, in the order Isoëtales. This order is sometimes placed in the class Isoëtopsida, sometimes in the Selaginellopsida or Lycopsida. They are considered "fern allies".

Quillworts are mostly aquatic or semi-aquatic. They feature reed-like or quill-like erect leaves arising from a central corm. They are heterosporous.

Quillwort species are very difficult to distinguish by general appearance. The best way to identify them is by examing the megaspores under a microscope.