1) Aquatic fern 2) Pilularia globulifera 3) Water fern 
• (n.) Any plant of the genus Pilularia; minute aquatic cryptograms, with small pill-shaped fruit; -- sometimes called peppergrass.
(from the article `fern`) ...in sporocarps (nutlike receptacles) along petiole; heterosporous.Family MarsileaceaeThree genera—Marsilea (waterclover), Pilularia, ... ...years old have been grown successfully to give rise to new sporophytes. Marsilea, with about 50 species, has cloverlike leaves with four leaflets ... [2 related a...
Pill'wort` noun (Botany) Any plant of the genus Pilularia ; minute aquatic cryptograms, with small pill-shaped fruit; -- sometimes called peppergrass . 
[n] - European water fern found around margins of bodies of water or in wet acid soil having small globose sporocarps
Pilularia globulifera noun European water fern found around margins of bodies of water or in wet acid soil having small globose sporocarps