Syn.: Ambrosinia retrospirale Roxb., A. uniloculare Roxb., Cryptocoryne unilocularis (Roxb.) Kunth, C. roxburghii Schott, C. dalzellii Schott.

Rhizome stout, 0.5-1.5 cm thick, sometimes irregularly thickened. Stolons stout. The root system is strongly developed, with also upright roots that thicken on reaching above the soil, and the plant may form a carpet-like growth. Leaves linear to lanceolate, green, sometimes brownish, 15-40 cm long and 0.3-1.0(-1.5) cm wide (Fig. 7 A – B, 42); lamina smooth or somewhat undulate, main rib forming most of the blade especially in more narrow-leaved specimens, the lamina mostly without prominent lateral veins. Margin sometimes denticulate. Monsoon leaves terete, 10-15 cm long. Spathe 10-30 cm long, tube 5-20 cm long, slightly twisted; limb of the spathe (1-) 3-8 cm long, spirally twisted, occasionally short and more or less open, yellowish to greenish, with rather large reddish spots (Fig. 8, 21, Jacobsen 1982). Female flowers 4-7, with more or less horizontal, oval to roundish stigmas. Olfactory bodies irregularly lobed in the upper part. Male flowers 100-140.

Chromosome number: 2n = 36, 72.

Distribution: India (Fig. 6).

Habitat: Sandy and stony bottom in and along rivers, often in rivers that carry a lot of water during the rainy season (Fig. 20). More or less emerged during flowering (Oct.-Feb.).

Nomenclatural notes: During the years there has not been much controversy regarding the identity of C. retrospiralis in the strict sense. C. unilocularis has been described from India, its characteristics being a unilocular fruit (which must be a mistaken observation) and a limb of the spathe spirally twisted from just above the kettle, the limb being purplish with darker spots. This long spirally twisted limb is interpreted as a monstrous spathe of C. retrospiralis having non fused margins of the tube normally formed. C. dalzellii was described on the basis of some fruits and a leaf-fragment, the latter now being interpreted as belonging to another, non Araceous genus, and the fruits belonging to C. retrospiralis.

Notes: C. retrospiralis is the only species from the western part of India with a long tube of the spathe and a spirally twisted, smooth limb of the spathe; it is characterized by the large, more or less circular, red spots on the limb (Fig. 8). Only few live collections (7) have been available for study. However, herbarium material is well represented and many well-preserved specimens exist, giving a quite distinct picture of the species.