Sfrom mirbel. 2B3 



of Europe abounds in matter of a sweet quality ; in the 

 north, it contains an excess of acid. So long as the or- 

 ganic functions, which depend upon the degree or du- 

 ration of heat, can be carried on, the Ash and the Vine 

 continue to grow ; they grow even when those func- 

 tions are performed incompletely ; but their growth is 

 stinted. They finally disappear at that point where 

 the portion of warmth in the atmosphere, though still 

 equal to prevent the freezing of the sap, is no longer 

 able to stimulate their organs or their frame into action. 

 All other vegetables, whose dimension and duration 

 subject them to the full severity of the frost, share the 

 same destiny at a greater or less distance from the 

 torrid zone, and in proportion as their constitutions re- 

 quire a greater or less degree of heat. So that nothing 

 is found near the Pole but such dwarf shrubs as are 

 sheltered under the snow in winter, or annuals anil 

 herbaceous species, endowed with so quick a principle 

 of life, as to rise, flower, and fruit within the space of 

 three months ; or some agamous and cryptogamous spe- 

 cies, which adapt themselves to all degrees of temper- 

 ature, and are consequently the last organic forms un- 

 der which vegetable life is to be described. 



Heat and moisture united are highly favourable to the 

 growth of plants. No countries are more abundant in 

 herbaceous vegetables, or better wooded than Senegal, 

 Guinea, and Cayenne, where both these props of veg» 

 tation are in the plenitude of their force. Experiments 

 made with the hygrometer prove that the moisture of 

 the atmosphere increases as we approach the Equator. 

 In hot climates, when the sun sinks below the horizon, 

 the watery exhalations condensed, are returned to the 

 earth in the form of dew, that moistens the surface of 

 the foliage, and feeds those vegetables in which the ab- 



