16 MINUTES OF 



O.i the component Principles of Vegetables. 



Til E various substances which afford food to plants, are changed by the or- 

 ganization of the vegetable; from which there results a fluid generally distributed, 

 and known by the name of sap. This juice, when conveyed into the several parts 

 6f the plant, receives an infinity of modifications, and forms the several humours 

 which are sepxrated and afforded by the organs. It is to these component princi- 

 pies chiefly that I am at present about to direct your attention; and I shall endea- 

 vour in my examination to follow the most natural order. These principles are 

 I. Mucilage. IX. Ax; ids. 



II. Oils. X. Alkalis. 



III. Resins. XI. Coloring Matter, 



IV. Balsams. XII. Pollen or fecundating Powder. 

 - V. Gum Resins. XIII. Honev. 



VI. Feculum. XIV. Lignum. 



VII. Gluten. XV. Extract. 



VIII. Sugar. 



I. Concerning INIucilage. 



INIucilage appears to constitute the first alteration of the alimentar}'^ juices 

 in vegetables. It is viscid and insipid. It affords, by distillation, — pyro-niucous- 

 acid, — a large proportion of water, — a small portion of a brown^ thick oil. — « 

 and a mixture of carbonic acid-gas with gas-hydrogen. It is soluble in water, 

 M^hether hot or cold : it does not absorb oxygen from the atmosphere: desiccation 

 gives it the hard and brittle form of gum. 



Mucilage is sometimes found almost entirely alone, as in mallows, the seeds 

 of the xvild quince, Unseed, the seeds of thlaspi, &g. Sometimes it is combined with 

 substances insoluble in water, which it keeps suspended ia the form of an emul- 

 sion; as in the eiiphorbium, celandine, the convolvulus, and others. In other in- 

 stances it is united with an oil, and forms the fat oils. Frequently it is uni||d with 

 sugar; as in i\\<^ gramineous seeds, the sugar-cane, maize, carrot, &c. It is likewise 

 found cotifounded with the essential salts, with excess of acid, as in barberries, 



