These are also known as Water Caltrops. They are the seeds of several species of water plants of the genus Trapa, of the Evening Primrose family {Onagraceae).

There are several species of these nuts. In Southern Europe there is a species called Jesuit nut. In China, they are called Ling, and are extensively used as an article of food. In India and Ceylon there is a nut called "Singhara-nut," which is closely allied to the water chestnut, and is probably a variety of the same species. Occasionally some have been imported and sold, but more for curiosities than for eating.

The seeds are of a dark-brown color, and of the form and size shown in the cut, resembling in miniature the skull of an ox, with abbreviated horns. When fresh, the kernels have an agreeable, nutty flavor.

Water Chestnut.

Water Chestnut.