Description from Flora of China
Herbs, amphibious, monoecious. Rhizome creeping, stoloniferous (usually subterranean). Leaves in a rosette, linear to spatulate to oblanceolate to cordate; veins arching from base of blade and connected by transverse veinlets. Peduncle very short, elongating at maturity. Spathe tubular with margins fused for most of length, proximally swollen forming a chamber (kettle) enclosing spadix; limb varying in shape, a collar or collar zone often present, in some species limb spirally twisted. Spadix at first fused at apex to base of spathe flap closing kettle (later breaking loose), much shorter than spathe; basal part with naked, connate gynoecia; intermediate zone naked; male zone apical; appendix conic, short. Female flowers 4-8, each 1-loculed; ovules many, subbasal (adaxial); styles free; stigma globose to elongate. Olfactory bodies immediately above stigmas regular or irregular structures. Male flowers naked; stamens solitary; thecae each dehiscent by an apical pore. Fruit syncarplike, multiple; each part ultimately splitting at adaxial part and becoming star-shaped, follicle-like; a few species splitting in a septicidal/septifragal-ceratium-like way. Seeds many, ellipsoid, small; endosperm usually copious.
Cryptocoryne cruddasiana Prain (J. Asiat. Soc. Bengal, Pt. 2, Nat. Hist. 69: 174. 1901; C. retrospiralis (Roxburgh) Kunth var. cruddasiana (Prain) de Wit; C. burmensis Rataj) occurs in N Myanmar, where it grows on riverbanks. It has not yet been recorded from China but may be distinguished as follows. Leaves strap-shaped, up to 30 × 0.5-1 cm, smooth to somewhat undulate at margin (sometimes also finely denticulate), green to brownish marmorate, apex rather abruptly acute; leaves disappearing during rainy period or becoming small, 2-4 cm, and terete. Spathe 8-12 cm; kettle 2-2.5 cm, with a constriction just below male flowers, proximally whitish, distally purplish and also with alveolae in wall; tube 4-5 cm, grayish outside; limb to 3.5 cm, upright to somewhat bent backward, with irregular, purplish or red-brown, rounded protuberances sometimes ± transversely oriented, base color of surface dark yellowish to red-brown, throat spotted, collar absent. Spadix: female flowers 5 or 6, with vertical, elliptic stigmas. Olfactory bodies cream-colored, finely spotted, irregularly lobed to subtoothed. Male flowers 80-120. Fruit not seen. Fl. Dec-Feb. 2n = 36.
More than 50 species: tropical Asia, from India to Malesia; one variable species in China.
(Authors: Li Heng (李恒 Li Hen); Niels Jacobsen)