4. Ceratopteris Brongniart, Bull. Sci. Soc. Philom. Paris. 8: 186. 1822.
水蕨属 shui jue shu
Authors: Youxing Lin & Shigeo Masuyama
Furcaria Desvaux; Parkeria Hooker; Teleozoma R. Brown.
Plants annual, juicy, aquatic. Rhizome erect, short, with thick roots, dictyostelic, with scales at apex; scales broadly ovate or cordate to peltate, entire, thin, brownish hyaline. Fronds clustered, dimorphic; stipe green, ± expanded, semicylindrical, fleshy, smooth, with sparse scales, with many longitudinal ridges on surface and many small vascular bundles inside. Sterile lamina green, ovate- to lanceolate-triangular, thinly herbaceous, simple or pinnate; ultimate lobe broadly lanceolate or loriform, entire, acute at apex; veins anastomosing; gemmae occasionally formed in axils of pinnae, brownish, small, ovate, resulting in juveniles through asexual propagation. Fertile lamina similar in morphology to sterile lamina but normally taller, divided more deeply and finely; ultimate lobe reflexed toward costa to enclose sori, green when young and brownish when old, linear to siliquiform; rachis green, with longitudinal ridges, deplanate when dry. Sori attached along costa, narrowly linear, covered with reflexed margin of lobe. Sporangium large, subsessile; annulus broad, vertical, consisting of 0-70 incrassate cells; trilete mark obvious or not. Spores 16 or 32 per sporangium, large, tetrahedral, trilete, with fine, parallel ridgelike ornamentations. x = 13(39).
Four to seven species: tropics and subtropics; two species in China.
The young fronds are used as a vegetable. In China, the rhizomes and fronds are used medicinally for treating fetal toxins and phlegm buildup.
Both species of Ceratopteris in China have shown significant declines in their distributions and are regarded as endangered. This is due to the loss of suitable aquatic habitats and decline in water quality of those that do survive (Y. H. Dong et al., Amer. Fern J. 102: 136-146. 2012).