L" 



ing matter may be made by digesting solutions of gall- 

 nuts with chalk: a green fluid is obtained, which be- 

 comes red by the action of an acid; and has its green 

 colour restored by means of alkalies. 



The yellow colouring matters of flowers are the 

 most permanent; the carthamus contains a red and a 

 yellow colouring matter; the yellow colouring matter 

 is easily dissolved by water, and from the red, rouge 

 is prepared by a process which is kept secret. 



The same substances as exist in the solid parts of 

 plants are found in their fluids, with the exception of 

 woody fibre. Fixed and volatile oils containing resin 

 or camphor, or analogous substances in solution exist 

 in the cylindrical tubes belonging to a number of 

 plants. Different species of Euphorbia emit a milky 

 juice, which when exposed to air deposit a substance 

 analogous to starch, and another similar to gluten. 



Opium, gum elastic, gamboge^ the poisons of the 

 Upas Antiar and Tieute, and other substances that 

 exude from plants, may be considered as peculiar 

 juices belonging to appropriate vessels. 



The sap of plants, in general, is very compound 

 in its nature; and contains most saccharine, mucilagin- 

 ous, and albuminous matter in the alburnum; and 

 most tannin and extract in the bark. The cambium, 

 which is the mucilaginous fluid found in trees between 

 the wood and the bark, and which is essential to the 

 formation of new parts, seems to be derived from these 

 two kinds of sap; and probably is a combination of 

 the mucilaginous and albuminous matter of one, with 

 the astringent matter of the other, in a state fitted to 

 become organized by the separation of its watery parts 





