64 VITAL FUNCTIONS OF PLANTS. [LKCT. II. 



Vegetables require different degrees of tempera- 

 ture for the preservation of their vitality. The 

 plant that flourishes under the ardent beams of a 

 tropical sun, would quickly perish if exposed to 

 the keen air of a northern latitude ; while the 

 Norwegian Fir, which raises its luxuriant head 

 green amidst the waste of Arctic snows, would 

 sicken, drop its leaves, and stand a lifeless trunk, 

 if removed to the torrid zone. But living vege- 

 tables, as well as animals, gradually accommodate 

 themselves to change of climate ; although they 

 retain their old habits for some time after their re- 

 moval, and by slow degrees only are naturalized 

 to new situations. Thus a fruit-tree, for instance, 

 which has been reared in a hothouse, and after- 

 wards planted in the open air, will, in the fol- 

 lowing season, expand its buds at the same time 

 that it used to do, and so expose them to inevi- 

 table destruction ; but after a few seasons, the na- 

 tural habit of its species will overcome the acquired 

 one of the individual, and the buds will remain 

 shut up till the genial warmth of the returning 

 sun, in spring, swells and expands them into 

 leaves*. This power of plants, which naturalizes 

 them to different climates, has enabled human in- 



* Rice, which is a native of the torrid zone, has gradually 

 travelled to Germany, where it is now cultivated ; but Rice 

 brought direct from the south of Italy will not vegetate in 

 Germany. 



