What is "water caltrop"

Water chestnut \Wa"ter chest"nut\ (Bot.) The fruit of Trapa natans and Trapa bicornis, Old World water plants bearing edible nutlike fruits armed with several hard and sharp points; also, the plant itself; -- called also water caltrop.

n. 1 An East Asian water plant with a horn-like nut, (taxlink Trapa bicornis species noshow=1). 2 The nut from this plant.

n. a variety of water chestnut [syn: Jesuits' nut, Trapa natans]

The water caltrop is any of three extant species of the genus Trapa: Trapa natans, T. bicornis and the endangered Trapa rossica. It is also known as water chestnut, buffalo nut, bat nut, devil pod, ling nut, lin kok, ling kio nut, or singhara.

The species are floating annual aquatic plants, growing in slow-moving water up to 5 m deep, native to warm temperate parts of Eurasia and Africa. They bear ornately shaped fruits, which in the case of T. bicornis resemble the head of a bull or the silhouette of a flying bat. Each fruit contains a single very large, starchy seed. T. natans and T. bicornis have been cultivated in China and the Indian subcontinent for at least 3,000 years for the edible seeds.