Proc. Acad. Nat. Sci. Philadelphia 98: 96. 1946.
Perennials. Stems prostrate, 15–60 cm, hairy. Leaves hairy; blade base broadly cuneate to truncate, margins entire, apex rounded. Pedicels 17–51 mm. Flowers: sepals 5, ovate to oblong, calyx bilaterally symmetric; corolla white with yellow throat, 10–14 mm; stamens 3, equal. 2n = 56.
Phenology: Flowering May–Oct.
Habitat: Marshes, ponds, pools, wet soil, wet ditches, rice fields.
Elevation: 30–1100 m.
Ariz., Calif., Nev.
Bacopa eisenii was reported by T. H. Kearney and R. H. Peebles (1960) based on a specimen labeled B. rotundifolia at ARIZ.