loo Sir A. Crichton on the [Feb. 



antediluvian vegetables, they throw the greatest and surest light 

 on the subject otits climate. 



That the similarity of any two Floras depends more on a simi- 

 larity of tempeiature than of soil, appears from a multitude of 

 facts. The Arnica Montana, for instance, is found on the low 

 marshy lands which border the Baltic, whereas in the south of 

 Europe it is only found on mountains, whence its specific name. 

 The Betula nana which is found on Mount Jura is met with in 

 Lapland at the foot of the mountains. The Betula Alba, or 

 common birch of this country, is found in the plains of Scotland 

 and of Russia, but in Portugal it only grows on the mountains. 

 When we come to plants of the same genus, but which are not 

 of the very same species, we find a similar analogy taking place 

 as demonstrative of the influence of climate ; thus many gentians, 

 and many of tlie pine and larch tribes, grow on the mountains 

 of South America as well as on the Alps, but not in the low 

 plains, much less the valleys. In many of the high plains of 

 Columbia, and almost under the equator, apple and willow trees, 

 and connnon furze, are found, while in the valleys under the same 

 parallel are found palms, 8cc. The plants of the North American 

 Flora which are most analogous to those of the Flora of Europe, 

 are found in analogous temperatures. 



Aitliough distant regions are often found to possess the same 

 temperature during a great part of the year, yet a multitude of 

 circumstances, independently of the three great co-ordinates, la- 

 titude, longitude, and elevation, may produce varieties of 

 climate, all of which we are incapable of enumerating, such as 

 the vicinity to extensive lakes or seas, the height and propin- 

 quity of mountains, the extent and direction of the land and sea, 

 winds, &c. ; and this explains why any two places under the 

 same parallel and elevation, and which have apparently similar 

 climates, may yet differ considerably in their effects on vegetable 

 life, and thus favour the growth of some new species. It is 

 probably owing to such causes that the plants of the Cape of 

 Good Hope and those of New Holland are not similar, although 

 their climates resemble each other in many respects. 



iVmong the fossil remains, however, of the plants which belong 

 to the coal formation, we scarcely find any variety, let the lati- 

 tude, longitude, or elevation, be what they may ; but supposing 

 a few species were discovered in any one district which were not 

 common to all, it would only prove the influence of a local cause, 

 the rest being all alike. Almost all genera and species of plants 

 belonging to that early period of the world, appear to have been 

 extremely limited ; they are remarkable for their similarity under 

 whatever parallels they are found. 



Every plant in the present world, independently of its natural 

 dwelling-place, has, as it were, a central spot in which it 

 flourishes best; and considering this spot as the centre of a 



