53 



CHAPTER X. 



OF THE SECRETED FLUIDS OF PLANTS. GRAFTING. 

 HEAT OF THE VEGETABLE BODY. 



THE sap in its passage through the leaves and bark 

 becomes quite a new fluid, possessing the peculiar 

 flavour and qualities of the plant, and not only yield- 

 ing woody matter for the increase of the vegetable 

 body, but furnishing various secreted substances, more 

 or less numerous and different among themselves. 

 These accordingly are chiefly found in the bark ; and 

 the vessels containing them often prove upon dissec- 

 tion 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 fre- 

 quently contain these fluids in the most perfect state, 

 nor are they, in such, confined to the bark, but depo- 

 sited throughout the substance or wood of the root, as 

 in Rhubarb, Rheum palmatum, Linn. Jil. Fasc. t. 4, 

 and Gentian, Gentiana lutea and purpurca, Ger. 

 Emac. 432, f. 1,2. In the wood of the Fir indeed 

 copious depositions of turpentine 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, 



