Tribulus
(Tribolos was the old Greek name used by Theophrastus, from treis, three, and bolos, a point; each carpel is often armed with three or four large spines). Caltrops. ORD. Zygophylleae. A genus comprising about fifteen species of loosely-branched, stove, greenhouse, or hardy herbs, dispersed over the warmer regions of the globe. Flowers white or yellow, solitary, pseudo-axillary, pedunculate. Leaves stipulate, opposite, or by abortion alternate. Most of these plants, several of which have been introduced, are weedy-looking subjects, and interesting only to a botanist. T. terrestris, a South European plant, is shown at Fig. 92.