Unusual Costa Rican Drift Fruit

After consulting many references and several noted authorities on legumes, the WAYNE'S WORD staff has finally solved the mystery drift fruit. The distinctive, woody, obovate fruit is flattened with raised veins resembling a thick, brown leaf. The dehiscent pods average about 2.5 to 4 inches (6-10 cm) in length. They come from Prioria copaifera Griseb., a tall tree in the Legume Family (Fabaceae: subfamily Caesalpinioideae). According to Allen (The Rain Forest Trees of Golfo Dulce, 1956) the trees are very abundant on the Atlantic (Caribbean) coast of Costa Rica along tidal estuaries and ascending to about 1,000 feet, forming nearly pure stands in some places. This would explain the common occurrence of the large, flattened one-seeded fruits on Caribbean beaches, from Tortugero and Limon and to Cahuita National Park. Like other large-fruited swamp species, such as Carapa guianensis, Pachira aquatica and Mora oleifera, the fruits are dispersed by ocean currents. According to Janzen (Costa Rican Natural History, 1983), the large seeds of these swamp species may be advantageous by rapidly producing tall shoots that place the seedling's first leaves above flood levels.

The trunks of Prioria copaifera exude a copious black gum when cut. Exposed heartwood is streaked with numerous dark resin canals that secrete the gummy resin. In fact, this species is one of the sources of a highly aromatic oleoresin called copaiba balsam (balsamo de copaiba). Oleoresins ("oil + resin") contain volatile terpenes called "essential oils" plus nonvolatile terpenes called "resins." Because of the volatile, strongly-scented terpene component, balsams are used in perfumes, incenses and medicines. The well-known "Canada balsam" is a natural turpentine collected from resin blisters on the bark of Abies balsamea, a cone-bearing tree of the northern United States and Canada.

The specific epithet copaifera is also the generic name for another tropical leguminous tree (Copaifera). The genus Copaifera includes about two dozen species of evergreen trees native to tropical America and Africa. Some of the trees are commercial sources of balsam resins and of lumber called "greenheart." The genus Copaifera is derived from "copal" (a name for resin or balsam) and "fero" (to bear). Two of the most commonly used species of copaifera balsam are Copaifera reticulata and C. officinalis.

Another Central and South American "copal" is the raw resin from the West Indian locust (Hymenaea courbaril), a large leguminous tree widespread throughout the New World tropics. This species also produces a large legume pod that commonly washes ashore on beaches of the New World tropics. The trunk and roots of this tree exude a sticky, yellowish terpene resin that forms hardened globs which become buried in the soil around massive trunks of dead trees. The hardened subterranean resin known as East African copal, which is commonly used in bead jewelry, comes from Hymenaea verrucosum, a tree that is closely related to the West Indian locust. In Chiapas, Mexico, Dominican Republic, and parts of Colombia and Brazil, the subterranean resin globs of ancient Hymenaea trees have transformed into amber through a remarkable chemical process requiring millions of years. During the polymerization process, the volatile terpenes escape and the nonvolatile terpenes bond together forming a hard plasticlike polymer that is resistant to natural decay processes and the ravages of time. Unlike copal resins and balsams, the amber is unaltered by organic solvents such as alcohol, acetone and ether. Although some copals will take a high polish, they contain volatile terpenes that gradually evaporate, causing the surface to become deeply crazed like the cracked mud of a dry lake bed.

So it appears that we finally have a name for the curious drift fruits that commonly float ashore on the beautiful beaches of Costa Rica.