m 



[ 209 ] 



covered with a box; after being both acted upon for 

 some time by boiling water, in the state of pulp, the 

 undissolved matter was dried, and exposed to the 

 action of warm alcohol. The matter from the green 

 leaves gave it a tinge of olive; that from the pale leaves 

 did not alter its colour. Scarcely any solid matter 

 was produced by evaporation of the alcohol that had 

 been digested on the pale leaves; whereas by the eva- 

 poration of that from the green leaves, a considerable 

 residuum was obtained, five grains of which were se- 

 parated from the vessel in which the evaporation was 

 carried on; they burnt with flame, and appeared partly 

 matter analogous to resin. 53 grains of woody fibre 

 were obtained from the green leaves, and only 31 

 from the pale leaves. 



It has been mentioned in the Third Lecture, that 

 the sap probably, in common cases, descends from the 

 leaves into the bark; the bark is usually so loose in its 

 texture, that the atmosphere may possible act upon it 

 in the cortical layers; but the changes taking place in 

 the leaves, appear sufficient to explain the difference be- 

 tween the products obtained from the bark and from 

 the alburnum; the first of which contains more carbo- * 

 naceous matter than the last. 



When the similarity of the elements of different 

 vegetable products is considered, according to the 

 views given in the third Lecture, it is easy to conceive 

 how the different organized parts may be formed from 

 the same sap, according to the manner in which it is 

 acted on by heat, light, and air. By the abstraction 

 ofoxygene, the different inflammable products, fixed 



E2 



