Aquatic. Flowers solitary in the middle and upper leaf-axils, or together with 1 or more reduced, cleisto-gamous flower(s), ☿, on a shortly cylindrical, up to ½ mm long pedicel. Sepals ± ovate obtuse or acute, serrate, with a brown margin, erect, 0.2-0.5 by 0.2-0.5 mm. Petals patent to recurved in anthesis, finally caducous, c. 2 mm long. Stamens 4, rarely 8; Ovary 2-celled, with 1(-2) ovules in each cell, sometimes 3-4-celled with 1 ovule in each cell. Fruit c. 1½ by 1 mm, with 2, sometimes 3 or 4 mericarps, smooth or indistinctly lengthwise lineolate, with a c. 0.5 by 0.4 mm long, erect or patent stalk.
Asia-Tropical, Australasia: Northern Territory (Northern Territory present); Queensland (Queensland present), Burnih Lake present, Calcutta Yeels present, E. India present, Haiphong present, Madura I present, Mareeba R present, N. Vietnam present, NE. Java present, Robinson R present
Australia (Northern Territory: Robinson R.; Queensland: Mareeba R.), E. India (Calcutta Yeels, T. THOMSON), N. Vietnam (Haiphong, BALANSA 1428); in Malesia: NE. Java (Madura I.: Burnih Lake). .
Two specimens from SE. Asia have erroneously been referred to the North American M. humile MORONG, which seems more closely allied to M. dicoccum than suggested by SCHIND-LER, who places them in different subgenera. The description and figure of ‘M. intermedium’ by TARDIEU-BLOT fits M. oliganthum (W. & A.) F.v.M., but the cited collection of BALANSA belongs to M. dicoccum.