A Horny Bull's Head
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Wayne's Word Noteworthy Plant For October 1995

A Horny Bull's Head

The feature plant for October 1995 produces a strange, horny pod that was presented to Professor Armstrong by a summer biology student. This bizarre horny fruit has two prominent, downcurved horns and superficially resembles the head of a bull. The fruit body has a woody, sculptured surface that resembles a face. To some people, the entire structure resembles a bat. It comes from an Asian aquatic plant often called "water caltrop" (Trapa bicornis). It is sometimes called water chestnut; however, this not to be confused with the crunchy, tuberous roots of a vegetable called water chestnut (Eleocharis dulcis) commonly served in Chinese restaurants. Other common names for this plant include Chinese horn nut and "ling kio" or "ling chio." It belongs to the water-caltrop family (Trapaceae) and includes the single genus (Trapa) with several closely-related species. The generic name Trapa is derived from calcitrappa, Latin name of the caltrop, in reference to the peculiar, horned fruits. During medieval times, a vicious weapon called a caltrop was used in European warfare. This was an iron device with four points so designed that one was always facing upward, whichever way it landed, to impale the hooves of enemy cavalry horses. A similar device was also used in World War II to destroy truck tires on enemy supply convoys. Actually, the widespread and more commonly-known water caltrop (Trapa natans) has a four-pronged fruit that more closely resembles the caltrop. The fruits of puncture vine also resemble a caltrop, especially when they impale your bicycle tires. In fact, this ubiquitous weed belongs to another unrelated plant family called the caltrop family (Zygophyllaceae).

Fruits of the Water Caltrop (Trapa bicornis).

Water caltrop plants are anchored to the bottom of lakes and ponds, and send to the surface a slender stem with a rosette of floating leaves. Like water hyacinths, the leaf stalks are inflated with air and are very buoyant. Solitary flowers are produced in the leaf axils followed by the strange horny fruits. Under the tough outer wall, the fruit contains a pulpy seed rich in starch. The fruits can be roasted or boiled like true chestnuts of the eastern United States. They are delicious sauteed with rice and vegetables. According to Joy Larkcom ("Oriental Vegetables," 1991), they contain toxins and should not be eaten raw. Seeds of some species are preserved in honey and sugar, candied, or ground into flour for making bread. In Italy Trapa natans is the main ingredient of a famous risotto (rice cooked in meat stock with shallots and butter). The unusual, bullhead pods of Trapa bicornis sometimes float down rivers and into the ocean where they occasionally drift ashore on Asian beaches. Local people make ingenious necklaces from the pods and sell them to tourists. With a backing attached to your lapel, they actually make a nice little emblem to wear on special occasions, or an attractive slide for a bolo tie.

According to Richard W. Spjut ("A Systematic Treatment of Fruit Types," Memoirs of the New York Botanical Garden Volume 70, 1994), the fruits of Trapa are classified as pseudodrupes." They are indehiscent with a thin, evanescent, fleshy exocarp and a persistent, stony endocarp. The English walnut is also classified as a pseudodrupe.

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