be this food composed of vvliat it may, 

 whether it differs in its kind as to the 

 tree taking it up, by which each plant 

 selects a peculiar sort or not, (a subject of 

 investigation for the curious,) it will suf- 

 fice for our purpose to know that it is 

 conveyed in a liquid state, and that it is 

 raised up through the above-described 

 vessels by the assistance of other tubes 

 filled with air, wliich becoming rarefied 

 by heat, act on the sap-vessels, and pro- 

 pel this liquid upwards. The sap, after 

 it has passed through the trunk and 

 branches, enters the leaves through the 

 footstalk, when it is exposed to the action 

 of the sun and light, and here it is ob- 

 served to be filtered, concocted, and 

 separated. The upper side of the leaf 

 receives the rays of the sun, and the 

 lower side, composed of pores, is the or- 

 gan of perspiration, which has been found 

 to be very copious in trees. And here 

 the extraneous parts being thrown off, 

 the finer are rendered fit for passing into 

 other tubes, which descend also througii 

 the footstalk. This finer fluid, returning 

 B 3 



