240 THE GEOGRAPHY 



extended northward. Higher up, the Fir forms the woody 

 vegetation ; but where even the easily satisfied Birch will no 

 longer thrive, a short but at least occasionally warm sum- 

 mer, allows of the culture of the quick-growing Barley. 

 It is not difficult to find the explanation of all this series 

 of facts; they are altogether dependant on climatal 

 influences, and an accurate investigation of the conditions 

 of temperature quite suffices to afford an explanatory account 

 of all these circumstances. 



Very different is it with the following phenomena. 

 From the southern point of Africa to the North Cape in 

 Mageroe, the Heaths extend throughout the Old World, 

 merely leaping over the proper tropical regions. With the 

 same latitudes, the same climate and similar conditions of 

 soil, we find not a single species of true Heath in all 

 America. Other allied plants replace them, plants which 

 at least belong to the same family (the Ericacece) ; but if 

 we go to Australia, we find under corresponding conditions, 

 not one Ericaceous plant, but in their place appears an 

 allied, but wholly peculiar family of plants, the Epacris 

 tribe. In a little corner of Asia grows the Tea-shrub, 

 and it is certainly not the absence of corresponding climatal 

 influences in all the rest of the world that confines the Tea 

 to China. In a small girdle on the Andes of the northern 

 half of South America, grows the race of Peruvian Bark 

 trees : is there no spot on all the earth in which the like 

 conditions of temperature and soil coincide? Enough, 

 even one single example would suffice to call attention to 

 the fact, that there exists upon the globe a mode of distri- 

 bution of plants, which is not produced by the conditions 

 of vegetation at present understood, nor can be explained 

 by them. We here obtain, side by side, two wholly dis- 

 tinct groups of known circumstances, which refer to the 



