Water-Caltrops, or Trapa natans, L. a valuable exotic, originally from Asia, though likewise growing wild in the ponds and ditches or Germany: its fibrous roots strike deeply into the soil; and, when the stalk, attains the surface of the water, its extremity presents a pyramidal bud, which, on the access of air, unfolds and spreads the convoluted leaves. - The plant flowers in June or July ; and produces its excellent fruit in August or September:
Although the water-caltrops be, on the Continent, considered as a troublesome weed in lakes and fish-ponds, yet we are persuaded that it may, with great advantage, be introduced into many marshy situations, especially those destitute of fish; to which animals it is certainly pernicious. The kernel contained in the nut of this aquatic vegetable, may be eaten, either raw or boiled : when dried and reduced to flour, it affords one of the most nutritive ingredients in broths, puddings, and other culinary dishes. Pliny informs us (book xxii. chap. 12, ) that the ancient Thracians converted this fruit into bread: and fed their horses with the leaves. - Formerly, the back roots of this luxuriant plant were reputed to be poisonous ; but it has lately been ascertained, that the Japanese boil and eat them, generally, in their daily soups.