298 BOTANY AND PHARMACOGNOSY. 



pharmacopoeias and known as Balsam of Tolu) which occurs 

 in schizogenons cavities in the bark of young twigs, and is ob- 

 tained by incising the bark, it being usually collected in 

 gourds. The balsam consists of 75 to 80 per cent, of resin, which 

 is a compound of tolu-resinotannol, cinnamic and benzoic acids; 

 18 to 20 per cent, of free cinnamic acid; 0.2 to i per cent, of a 

 volatile oil ; and 0.05 per cent, of vaniUin. A good tolu balsam 

 is also obtained from T. peruifera growing in the northeastern 

 part of South America. 



Tohiifcra Pcreirce is a tree about 15 M. high, which has a 

 short trunk and begins to branch at a height of 2 or 3 M. It 

 otherwise resembles T. Balsamuin. It is found over the whole of 

 Northern South America, extending through Central America 

 to Mexico, and is cultivated in Singapore. The balsam, which 

 is formed as a result of injury to the trunk, consists chiefly of 

 esters of benzoic and cinnamic acids, some free cinnamic acid, and 

 vanillin. A very fragrant vanilla-like balsam is obtained 

 from the fruit of this same plant, and in San Salvador it is known 

 as white Peru balsam to distinguish it from the black Peru balsam 

 obtained from the trunk. 



Physostigma venenosum is a woody climber. The leaves are 

 3-foliate, the leaflets being ovate-acuminate ; the flowers are violet 

 in color and in axillary racemes ; the fruit is a broadly linear, 

 somewhat flattened, distinctly veined, dehiscent pod which tapers 

 at both ends, and contains two or three seeds (Fig. 189). The 

 seeds are official as Physostigma (p. 438). 



The blue coloring principle indigo is mostly obtained from 

 the herbs Indigofera tinctoria and /. Anil which are indigenous , 

 to, and cultivated in tropical and sub-tropical countries. It is 

 prepared by extracting the leaves with water. The glucosidal 

 principle indican (or mother-substance of indigo blue) undergoes 

 oxidation and the insoluble indigo blue separates out. This is the 

 commercial indigo. A similar principle is found in the wild indigo 

 (Baptisia tinctoria) of the United States and Canada; the leaves 

 of Robinia Pseudacacia of North America ; several species of 

 Psoralea and Amorpha, as well as some other Legumindsse. It is 

 also found in other families, as in Polygonaceae, Crucifersei As- 

 clepiadacese, and Apocynacese. 



