Hygrophila costata

This plant is native to South America, and its stems reach 25-60 cm in length, while its leaves are 10 cm long. In its submerged state, Hygrophila costata has relatively narrow leaves that are clustered together. Plants sold in stores are typically grown in their emersed state and have more rounded leaves with larger spaces between them.
Hygrophila costata was called Hygrophila corymbosa 'Angustifolia' until recently.