IIG ZYGOPHYLLACE^. 



Fruit depressed, five-angular, tuberculate or spiiiose, sep- 

 arating at maturity into five thick and bony indehiscent 

 cocci, leaving no central axis ; the cocci divided internally 

 by oblique transverse septa into from three to five one-seeded 

 compartments. Seeds obliquely pendulous, oblong-obovate ; 

 the membranaceous testa marked with a filiform raphe and 

 a circular chalaza. Albumen none. Embryo conformed to 

 the testa : coxyLEDONs oval, fleshy, parallel with the raphe 

 and axis: radicle short, conical, centripetal-superior. 



Herbs diffuse or procumbent ; with abruptly pinnate op- 

 posite leaves, one of which alternately is smaller than the 

 other. Stipules subulate or lanceolate, membranaceous. 

 Flowers solitary, on terminal peduncles, which become lat- 

 eral and as if axillary from the smaller leaf of each pair, 

 owing to the repeated evolution of the branch from the axil 

 of the larger leaves. Petals yellow, or rarely white. 



Etymology. Tpi^oKos, an ancient name of Trapa natans, so called from 

 its triangular prickly nut (from rpis, three, and jSaXXw, fo strike or wound), 

 also applied to T. terrestris, on account of its prickly fruit. 



Geographical Distribution. A genus of a few species indigenous to 

 the Mediterranean region, and within the tropics of the Old World, and of 

 one indigenous to tropical America, which extends northward to the coast 

 of Florida and Texas ; namely, T. cistoides, L., which has been incorrectly 

 referred to Kallstromia. 



PLATE 145. Tribulus cistoides, Linn.;' — a flowering branch (from 

 Florida), of the natural size. 



1 . Diagram of the flower. 



2. The pistil, with the hypogynous disk and glands, magnified. 



.?. Vertical section of the same, with the stamens, petals, &c. in place. 



4. An ovule detached and more magnified. 



5. The 5-coccous fruit, of the natural size. 



6. Vertical section of one of the cocci and of its seeds, enlarged. 



7. A detached seed magnified ; the raphe toward the eye. 



8. Vertical section of the same, cutting through the raphe. 



9. Embrvo detached and mao-njfied. 



