94 ON THE USE AND OFFICES 



that in an open vessel, containing a liquid, the 

 greater the surface of the liquid exposed, the 

 greater will be the quantity evaporated in a 

 given time, and the greater the quantity of ex- 

 tractive matter prepared ; so it is with vege- 

 tables, the greater the surface of leaves and 

 branches exposed to the light, and the influence 

 of the sun and air, the greater the quantity of 

 fluid disposed of, by being digested, appro- 

 priated, and expelled ; and the greater the quan- 

 tity, and richer the quality of food and sap 

 supplied, and raised by capillary attraction, or 

 otherwise ; the greater the quantity and richer 

 the quality of the matter furnished, to be re- 

 tained 'and appropriated by every part of the 

 plant to its various puiposes, either of genera- 

 tion, or of substantial increase. 



Again, the fruit of a plant being considered, 

 as requiring for its formation, a regularly pro- 

 portioned arrangement of its organs, and a due 

 supply of healthy sustenance, we may trace the 

 progress of nature to this effect, on the fore- 

 going principles, more clearly than by the doc- 

 trines of circulation, gravitation, or any other 

 theory that has been suggested ; and we may 

 conclude that it is with vegetables, as with ani- 

 mals, required to sustain health, that the grand 



