HARMONIES OF VEGETATION. 2G1 



transmitted from one part to another through the medium 

 of the vessels for circulation. 



The circulation of the sap is in particular assisted by caloric, 

 which is a stimulant, by light, electricity, the rarefaction and con- 

 d'-nsation of air in the vessels, and by capillary attraction. 



22. There are three modes of excretion in plants; 

 the first called exudation, the second respiration, and 

 the third transpiration. 



23. Exudation is the process by -which the circulating 

 fluids of the plant, are converted into proper or pecu- 

 liar juices. 



By exudation, therefore, the overplus common jnices of the plant, 

 are not wasted by transpiration, but wonderfully changed by the 

 laws of vegetation, to furnish many valuable aud elegant additions 



24. Respiration, which includes also absorption, is 

 the function by means of which, oxygen and carbonic 

 acid gas are evolved. 



Plants, like animals, require air to breathe or to support their vi- 

 tality; but Nature, always the greatest economist and unerring in 

 her calculations, has so ordained, that the atmospheric air which 

 has been injured by animal respiration, shall be calculated to conti- 

 nue vegetable life ; and on the other hand, that the respiratory 

 gases of plants shall be adapted to the wants of animals. Thus we 

 perceive, how harmonious these two grand principles combine to 

 equalize the wants of both. 



25. Transpiration is the economy by which plants 

 emit such particles as are unnecessary or useless. 



The transpiratory fluid is generally composed of a certain quantity 



