Aquatic perennial. Inflorescence terminal, composed of digitate or subdigitate racemes. Racemes ± flattened, tardily disarticulating; internodes and pedicels thickened, clavate, hollowed at the summit. Sessile spikelet: callus truncate; lower glume produced into a long flattened tail; lower floret male with hyaline lemma and palea; upper lemma entire and awnless. Pedicellate spikelet similar to the sessile.