Ceratopteris thalictroides

Ceratopteris thalictroides is a fern in the genus Ceratopteris, which is one of just two genera that make up the subfamily Parkerioideae within the family Pteridaceae. It goes by several common names, including water sprite, Indian fern, water fern, oriental waterfern, and water hornfern. In the Philippines, it is called pakung-sungay, meaning "antler fern" or "horn fern."

Description

This species is found across tropical and subtropical regions worldwide, ranging as far north as Korea and as far south as western Australia. It typically grows rooted in mud, and its appearance and size can vary. The stipes of mature plants are spongy and filled with air, measuring 3–15 mm in diameter, and the stipes are 4-60 cm long including its stipe. Fertile fronds are pale green, turning brown when mature, and can reach 15–100 cm or more in length, including the stipe, to 40 cm long.

Proliferous or dormant buds, covered in overlapping dark scales and winged, appear in the axils of the fertile pinnae. The pinnae are deeply incised, with sterile segments 2–15 mm by 10–30 mm and fertile segments 1–2 mm by 10–80 mm. Chromosome counts vary by region: the north type and third type have 2n=126, while the south type has 2n=154, distinguishing it from other species. Ecologically, Ceratopteris thalictroides is often found near stagnant water or in still pockets along slow-flowing rivers, in swamps, swamp forests, sago swamps, marshes, and natural or man-made ponds.

Ecology

It thrives in full sun to moderate shade, from sea level up to 1,300 meters (mostly below 500 meters). It frequently masses on logs or floating vegetation, and has been recorded growing among the pneumatophores of freshwater mangroves (Sonneratia). In some areas, it shows seasonality, reaching maturity and shedding spores during the dry season, by which time most sterile fronds have been lost. It is functionally an annual in the wild, repopulating from spores the next season, but can live indefinitely in cultivation and reach full maturity in 29 days.

Culinary

The fronds are cooked and eaten as a vegetable in Madagascar, Swaziland, New Guinea, Nepal, Vietnam, and other parts of Asia, often used like watercress. In Malaysia and Japan, uncurled fronds are used in salads. However, some ferns are potentially carcinogenic when eaten, and this may apply to Ceratopteris thalictroides.