54 RESINOUS SECRETIONS. 



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 different heads. 



Gum or mucilage, a viscid substance of litde flavour 

 or smell, soluble in water, is very general. When su- 

 perabundant, it exudes from many trees in the form of 

 large drops or lumps, as in Plum, Cherry, and Peach- 

 trees, and different species of Mimosa or Sensitive 

 plants, one of which yields the Gum Arabic, others 

 the Gum Senegal, &c. 



Resin is a substance soluble in spirits, and much 

 more various in different plants than the preceding, as 

 the Turpentine of the Fir and Juniper, the Red Gum 

 of New South Wales, produced by one or more spe- 

 cies of Eucalyptus, Bot. of N. HolL t. 1 3, and the 

 fragrant Yellow Gum of the same country, see IVhites 

 Voyage, ^35, which exudes spontaneously from the 

 XanthorrJioza Hastile. Most vegetable exudations 

 partake of a nature between these two, being partly 

 soluble in water, pardy in spirits, and are therefore 

 called Gum-resins. The milky juice of the Fig, Spurge, 

 &c., which Dr. Darwin has shown, and which every 

 body may see, to be quite disdnct from the sap, is, 

 like animal milk, an emulsion, or combination of a 

 watery fluid with oil or resin. Accordingly, when suf- 

 fered to evaporate in the air, such fluids become resins 

 or guuhresins, as the Gum Euphorbium. In the Ce- 



