WATER-CALTROPS, or Trapa natans, L. a valuable exotic, originally from Asia, though likewise growing wild in the ponds and ditches of 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 black 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.