SEEDS AND PLANTS. 131 



3. Tobacco is formed from the leaf of the nicoliaiia tahacum, a 

 native of Tabaco in Mexico, from which it receives its name. 

 It is a well known, and much used narcotic poison. It con- 

 tains at least eighteen different substances. IsTicotina is the 

 cause of its poisonous effects. 



4. Fox-glove, the digitalis purpurea, is a well known vege- 

 table, the leaves of which were introduced into medicine by 

 Dr. Withering. 



5. Tea is composed of the dried leaves of the thea bohea, and 

 thea viridis, natives of China and Japan. The different varieties 

 of tea, are all derived from these two species. The leaves of 

 this plant are not fit for use, until the shrub has vegetated three 

 years. The leaves are collected and exposed to the steam of 

 boiling water, and every leaf is then rolled up with the hand, 

 put upon plates of copper, and held over the fire, until they are 

 shrivelled. To this heating process tea owes its peculiar flavor. 

 Its uses are well known. It is a powerful stimulant, acting up- 

 on the nervous system, and producing an exhilarating effect. 



6. James' tea is the leaf of the ledum latifolium, a native of this 

 country. 



7. Paraguay tea is the leaf of a native plant of South Amer- 

 ica, of the holly genera, and is used as a tea. It is a stimulant, 

 and, if used in excess, occasions intoxication and delirium, tre- 

 mens. 



8. Isatis tinctoria, or woad, is the plant from which indigo is 

 olbtained. 



9. Asparagus officinalis is a valliable vegetable, the young 

 shoots of which are used for food. 



V. Seeds and fruits constitute the most important articles 

 of food. They contain all the elements necessary for the sup- 

 port of animals. 



1. Wheat is the seed of the triticum hybernum, winter wheat, 

 and T. aestivum, or summer wheat, the most important of all the 

 smaller grains. Two or three other species have been cultiva- 

 ted. Its properties and uses are well known. A sample of 

 French wheat, analyzed by Vauquelin, yielded seventy-one parts 

 of starch, ten of gluten, five of sugar, three of gum, and ten of 

 water in one hundred. 



2. Rye is the grain of the secale cereale. It is subject to the 

 disease called ergot, which is a species of fungus plants, of a 

 long, black appearance, blunt angles, and about one inch in 



