Trapa

The water caltrop is any of three extant species of the genus Trapa: Trapa natans, Trapa bicornis and the endangered Trapa rossica. It is also known as buffalo nut, bat nut, devil pod, ling nut, mustache nut, singhara nut or water chestnut. The species are floating annual aquatic plants, growing in slow-moving freshwater up to 5 metres (16 feet) 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 the edible seeds for at least 3,000 years....read more on Wikipedia.