References: Johnson in FNA (1993b).
A family of 3 genera and about 50 species, subcosmopolitan.
1. Leaves cloverlike, the 4 cuneate, obovate or wedge-shaped segments borne at the summit of the stipe; sporocarps ovoid......Marsilea1. Leaves grasslike, linear, the leaf blade absent, the stipe narrowly winged; sporocarps spherical......Pilularia
A genus of about 45 species, subcosmopolitan.
*Marsilea quadrifolia Linnaeus, European Water-clover. Pd (NC): shallow water of artificial impoundment; rare; native of Europe. Not seen fertile in NC. First reported for our area in 1992; sold in garden stores as an aquatic to be grown in water gardens, and likely to be encountered more widely in the future. [= C, F, FNA, G, K]
References: Dennis & Webb (1981).
A genus of about 5 species, subcosmopolitan.
Pilularia americana A. Braun, American Pillwort. Pd (SC): vernal pools and seepage areas on granitic flatrocks; rare. This peculiar plant has a puzzling distribution, being known from several disjunct regions: OR to s. CA; NE to TX; AR; TN; and GA to SC. The fragmented distribution may be at least partly explainable by the inconspicuous nature of the plant. It lacks a leaf-blade, the 1-8 cm long stipe being narrowly winged, appearing rather like an Isoetes or Juncus leaf. In vegetative condition, it may be recognized as a "fern" by the typical coiled ("fiddlehead") development of young leaves. The primary rhizome produces individual "fronds" at nodes, a short rhizome branch at each node also produces "fronds." First reported for our area in 1993 (Allison, pers. comm.). [= FNA, K, S]
Flora of the Carolinas and Virginia, Working Draft of 27 October 1997 -- KEY TO PTERIDOPHYTE GENERA. Alan S. Weakley. The Nature Conservancy, Southeast Regional Office, Southern Conservation Science Department.