156 



SEEDS 



TONCO BEANS 



(Semina Tonco) 



Source, &c. Tonco (tonka or tonquin) beans are the seeds of two 

 species of Dipteryx (N.O. Leguminosce) , viz. D. odorata, Willdenow, 

 and D. oppositi folia, Willdenow, both trees of considerable size, the 

 former a native of Guiana, the latter of Brazil. 



The tree produces an indehiscent drupaceous fruit about the size 

 of an egg, with a fibrous pericarp containing a 

 single brownish violet seed, about the size and 

 shape of an almond. The fallen fruits are 

 collected, split open and the seeds removed and 

 dried on flat rocks. Sometimes they are placed 

 upon the market without further treatment, 

 but large quantities are brought from South 

 America to Trinidad, where they are prepared 

 for the European and American markets. This 

 preparation consists in steeping them in rum, 

 removing the excess and drying the seeds. By 

 this treatment a white crystalline crust (of 

 coumarin) is produced on the surface of the 

 seeds ; the latter may therefore occur ' black ' 

 or ' frosted ' ; when dry they are packed in 

 cases or casks for shipment. 



Description. Tonco beans closely resemble 

 a Jordan almond in size and shape ; they, are 

 usually rather longer, varying from 3 to 4 cm. 

 in length, and differ from the almond in having 

 a nearly black, coarsely wrinkled surface which, 

 in the frosted seeds, is covered with minute 

 whitish crystals. The beans are rounded at one extremity but terminate 

 at the other in a broad, flat point, just below which on the obtuse 

 margin of the seed the micropyle may easily be discerned as a brownish 

 scar. Internally they are dark yellow, yellowish brown, or nearly 

 black, and consist of two large oily cotyledons, without endosperm, 

 enclosing a plumule with two folded leaves and a short thick radicle. 

 Tonco beans have a powerful and agreeably fragrant odour and an 

 aromatic pungent taste. 



? Constituents. The seeds owe their fragrance to coumarin, of which 

 they may contain as much as 3 per cent. 



Coumarin, coumaric or ortho-oxycinnamic anhydride, G 6 H 4 (CH) 2 OCO, forms 

 colourless, fragrant crystals melting at 67. It may be prepared synthetically 

 by heating together salicylic anhydride, acetic anhydride, and anhydrous sodium 



FIG. 87. Tonco bean. 

 Fruit cut verti- 

 cally, showing the 

 seed. (Planchon 

 and Collin.) 



