Pillwort [Latin pilula, a little ball, in reference to the spheric sporocarps]

David M. Johnson

Plants aquatic, commonly entirely under water and infrequently persisting on bare mud. Roots arising at nodes. Leaves filiform, terete, lacking expanded blades. Sporocarps subterranean, borne on unbranched stalks arising at bases of petioles, attached laterally to stalk apex (attached portion called raphe), lacking teeth; sporocarps densely to sparsely hairy, less so with age, dehiscing into 4 valves.

Species 6 (1 in the flora): North America, South America, Europe, Pacific Islands in New Zealand, Australia.

SELECTED REFERENCES

Dennis, W. M. and D. H. Webb. 1981. The distribution of Pilularia americana A. Br. (Marsileaceae) in North America, north of Mexico. Sida 9: 19--24. Petrik-Ott, A. J. and F. D. Ott. 1980. Pilularia americana new to Tennessee. Amer. Fern J. 70: 29--30.

Lower Taxon

• Pilularia americana A. Braun