Belongs to the monotypic genus; Subfamily: Podostemoideae.

Aquatic herbaceous, thalloid basal part, ribbon-shaped roots, closely attached to the rock or partially. Leaves simple, swollen at the base. Flowers solitary. Tilted capsule with 2 unequal valves, compressed laterally. Seeds small, reddish, ellipsoidal.

Endocaulos differs from the Madagascar Podostemaceae in the morphology of its stamens and fruits. Phylogenetically, it is related to the Malagasy genus Thelethylax (Kita & Kato, 2001).