TONCO 157 



acetate. It has been isolated from a variety of plants belonging not only to 

 Leguminosce, but several other natural orders, especially Graminece and Orchidece. 

 Cherry wood (Prunus Mahaleb, Linne), woodruff (Asperula odorata, Linne), 

 and melilot (Melilotus officinalis, Desvaux) owe their pleasant aroma to coumarin. 



Varieties. The chief varieties of tonco beans are the Angostura 

 and the Para, each of which may occur frosted or black ; the Angostura 

 beans are the larger and more valuable. 



Uses. Tonco beans find their principal use in perfumery ; they 

 are frequently mixed with vanilla beans in the preparation of extract 

 of vanilla. 



CALABAR BEANS 



(Semina Physostigmatis) 



Source, &C. Calabar beans are the ripe seeds of Physostigma vene- 

 nosum, Balfour (N.O. Leguminosce), a woody climbing plant indigenous 



A B 



FIG. 83. Calabar bean. A, side view, showing the sub-reniform 

 shape. B, edge, showing the long hilum. C, seed split open, 

 showing the concave cotyledons. (Maisch.) 



to the west coast of Africa, especially near the mouths of the Old 

 Calabar and Niger rivers. It ascends trees and, drooping down, bears 

 pendulous racemes of flowers. These are succeeded by legumes about 

 15 cm. in length, in each of which two or three large seeds are contained. 

 Calabar beans have long been used on the west coast of Africa as ' ordeal 

 beans. They became known in England in 1840 ; their power of 

 contracting the pupil of the eye was discovered by Fraser in 1862. 



Description. Calabar beans are dark reddish brown or chocolate- 

 brown in colour and average about 25 mm. in length and 12 mm. in 

 thickness. They are usually oblong-reniform in shape, being nearly 

 flat or only slightly convex on one side, but boldly curved on the other. 

 Along nearly the entire length of the curved side, and passing com- 

 pletely round one end of the seed, runs a broad, deep groove, the lips 

 of which are thickened and paler in colour, and the bottom of which 



