3. Plants producing 2 types of spores (male and female);
leaves with tiny ligule at the base. The two common species have
either flat or 4-angled strobili. The third species with round strobili
is endangered in Wisconsin, grows only on a few sites near Lake
Michigan where it may easily be mistaken for a moss, and is very
unlikely to be encountered by any but knowledgeable botanists.
3. Plants producing only one kind of spore;
leaves without a ligule at the base. The strobili are round, or
in four species they are lacking, with the sporangia located in
the axils of otherwise normal leaves, on round stems.