American Pillwort

Description

The pillwort, along with all other aquatic ferns in the order Salviniales, exhibits heterospory and forms hard, seed-like sporocarps, as do the other members of the order. The sporocarps are distinctly different from the closely related genus Marsilea because they are globose in Pilularia, while they are flattened in Marsilea. The ferns in the Pilularia genus also have lost their leaf blades, with only the grass-like stipe remaining. However, this plant retains the circinate vernation characteristic of most ferns.