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CHAPTER X. 



OF THE SECRETED FLUIDS OF PLANTS. GRAFTIXG. HEAT 

 OF THE VEGETABLE BODY. 



The sap in its passage through the leaves and l^ark 

 becomes quite a new fluid, possessing the peculiar fla- 

 vour and qualities of the plant, and not only yielding 

 woody matter for the increase of the vegetable body, but 

 furnishing various secreted substances, more or less nu- 

 merous and different among themselves. These ac- 

 cordingly are chiefly found in the bark ; and the vessels 

 containing them often prove upon dissection very large 

 and conspicuous, as the turpentine-cells of the Fir tribe. 

 In herbaceous plants, whose stems are only of annual 

 duration, the perennial roots frequently contain these 

 fluids in the most perfect state, nor are they, in such, 

 confined to the bark, but deposited throughout the sub- 

 stance or wood of the root, as in Rhubarb, lihcum pal- 

 amafam, Linn. Jil. Fasc. f. 4, and Gentian, Gentian 

 liitea and purpurea^ Ger. emac. 432, f. \^ 2. In the 

 wood of the Fir indeed copious depositions of turpen- 

 tine are made, and in that of every tree more or less of a 

 gummy, resinous, or saccharine matter is found. Such 

 must be formed by branches of those returning vessels 

 that deposit the new alburnum. These juices appear to 

 be matured, or brought to greater perfection, in layers 

 of wood or bark that have no longer any principal share 

 in the circulation of the sap. 



The most distinct secretions of vegetables require to 

 be enumerated under several diffcreiil heads. 



