154 FLA\'()RING AND BEVERAGE PLANTS 



quantity it often has upon the nervous system a marked 

 effect, which may be injurious or beneficial according to 

 circumstances. The coffee "bean" contains about 0.5-2% 

 of caffeine, dried tea leaves about 1-3%. Theobromine, of 

 which there is about 1.5% in the cacao seed, is found to be 

 scarcely soluble in the fluids of the bod}", and thus exerts 

 little if any effect. 



The most active constituent of each of the three beverage 

 plants we are considering is the aromatic substance to which 

 its pecuhar flavor is due. In black tea there is about .5%, 

 and in green tea about 1% of a volatile oil which is mainly 

 developed during the curing or preparation of the leaves for 

 market. The commercial value of a tea depends mainly 

 upon the flavor imparted by its volatile oil. This flavor is 

 carefully tested by experts who are known as "tea-tasters," 

 although curiously enough they smell rather than taste the 

 samples submitted to them. Even so, the effect of the vola- 

 tile oil upon the nervous system is so powerful as to cause 

 giddiness and headache if the "tasting" be continued more 

 than a few hours a daj^; and it is said that the most vigorous 

 cannot pursue the work for many years without suffering 

 serious consequences. The peculiar aroma of coffee is not 

 found in the raw "bean" but is developed during the process 

 of roasting; that of cacao arises during the process of fermen- 

 tation which the seeds undergo before they are ready for 

 market. In coffee the aromatic constituent is hardh" as 

 powerful as in tea, while in cacao it is so mild that vanilla and 

 various spices are added as flavoring to make chocolate. 



Finally, mention must be made of an astringent constituent 

 belonging to the class of substances known as tajinins. This 

 forms about 10%, of dry tea leaves. It is similar to the sub- 

 stance extracted from bark for tanning leather. Black ink is 

 commonly made by combining tannin with a substance con- 

 taining iron When taken with food in considerable quanti- 

 ties this astringent interferes Avith digestion. Prolonged boil- 

 ing extracts it in large amount from tea leaves; consequently 

 tea so prepared is most injurious. Steeping for a short time, 

 on the contrary, removes but little of the tannin, while it ex- 

 tracts practically all of the exhilarating and aromatic constit- 



