434 CAUSES LIMITING PROPAGATION. CHAP. X. 



tent: and it may be laid down as a botanical 

 axiom, that the more diversified the surface of the 

 country the richer will its Flora be, at least in the 

 same latitudes. It accounts also for the want of 

 correspondence between plants of different coun- 

 tries though placed in the same latitudes ; because 

 the mountains or ridges of mountains, which may 

 be found in the one and not in the other, will pro- 

 duce the greatest possible difference in the character 

 of their Floras. And to this cause we may ascribe 

 the diversity that often actually exists between 

 plants growing in the same latitudes, as between 

 those of the north-west and north-east coast of 

 North America, as also of the south-west and south- 

 east coast ; the former being more mountainous, the 

 other more flat. Sometimes the same sort of dif- 

 ference takes place between the plants of an island 

 and those of the neighbouring continent; that is, 

 if the one is mountainous and the other flat ; but 

 if they are alike in their geographical delimation, 

 then they are generally alike in their vegetable pro- 

 ductions. 



Cold and lofty situations are the favourite habitat 

 of most cryptogamic plants of the terrestrial cfass^ 

 especially the Fungi, Alga, and Mosses ; as also of 

 plants of theclass Tetr adynamia, and of the Umbellate 

 and Syngencsial tribes. Whereas trees and shrubs, 

 Ferns, Parasitic plants, Lilies, and Aromatic plants, 

 are most abundant in warm climates ; only this is not 

 to be understood merely of geographical climates, 



