4-30 CAUSES LIMITING PROPAGATION. CHAP. X. 



mates are often the same ; and hence also plants 

 Equate- that are natives of the equatorial regions cannot be 

 made to vegetate in high latitudes, except by 

 putting them into a hot-house and keeping up an 

 artificial heat This is known to every body who 

 is the least conversant in gardening, and forms one 

 of the most difficult branches of the art. Hence 

 it is impossible to naturalize the equatorial plants 

 in this climate such as the Palms, Pine-apple, and 

 others ; because the degree of cold naturally sub- 

 Tropical sisting in it would infallibly kill them. In like 



and polar . * 



plants, manner plants that are indigenous to the more tem- 

 perate regions, cannot be made to vegetate in the 

 equatorial regions, because the excessive heat of 

 such regions would destroy them. The Wheat and 

 Barley of Europe will not grow within the tropics ; 

 the same remark applies to plants of still higher 

 latitudes, such as those within the polar circles 

 which cannot be made to vegetate in more southern, 

 latitudes, nor can the plants of more southern lati- 

 tudes be made to vegetate there. 



Such is the case with plants in general, and such 

 are the boundaries which they cannot pass, con- 

 fining them to the peculiar habitat destined by 

 Inured by nature. But some plants may be inured to cli- 

 to opposite rciates of which they are not indigenous; and this 

 climates, seems ^ o b e mos t easily done in going from a hot 

 to a cold climate, particularly with herbaceous 

 plants. Because it often happens that the frosts of 

 winter are accompanied with snow which shelters 



