Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ulva, ae, f. [root or-, ol-; cf. origo], sedge: Ulva conferva, Linn.; Plin. 16, 1, 1, § 4; 17, 23, 35, § 209; 21, 17, 68, § 111; Cato, R. R. 37, 2; Col. 4, 13, 2; Verg. G. 3, 175; id. E. 8, 87; Ov. M. 4, 299; 6, 345; 8, 336; Hor. S. 2, 4, 42.