FLORAS OF DIFFERENT COUNTRIES. 359 



veyed to a distance through the air. When once they have 

 taken root, they become dependent on the soil and on the 

 strata of air surrounding them. Animals, on the contrary, can 

 at pleasure migrate from the equator towards the poles ; and this 

 they can more especially do where the isothermal lines are 

 much inflected, and where hot summers succeed a great degree 

 of winter cold. The royal tiger, which hi no respect differs 

 from the Bengal species, penetrates every summer into the north 

 of Asia as far as the latitudes of Berlin and Hamburgh a fact 

 of which Ehrenberg and myself have spoken in other works.* 

 The grouping or association of different vegetable species, 

 to which we are accustomed to apply the term Floras, do not 

 appear to me, from what I have observed in different portions 

 of the earth's surface, to manifest such a predominance of 

 individual families as to justify us in marking the geographical 

 distinctions between the regions of the Umbellate, of the Soli- 

 daginac, of the LabiataB, or the Scitaminea). With reference to 

 this subject, my views differ from those of several of my 

 friends, who rank among the most distinguished of the 

 botanists of Germany. The character of the floras of the ele- 

 vatejl plateaux of Mexico, New Granada, and Quito, of Euro- 

 pean Russia, and of Northern Asia, consists, in my opinion, 

 not so much in the relatively larger number of the species 

 presented by one or two natural families, as in the more com- 

 plicated relations of the co-existence of many families, and in 

 the relative numerical value of their species. The Gramineee 

 and the Cyperaceae undoubtedly predominate in meadow lands 

 and steppes, as do Conifera?, Cupuliferse, and Betulinese, in our 

 northern woods ; but this predominance of certain forms is 

 only apparent, and owing to the aspect imparted by the social 

 plants. The north of Europe, and that portion of Siberia 

 which is situated to the north of the Altai mountains, have no 

 greater right to the appellation of a region of Gramineae and 

 Conifer, than have the boundless llanos between the Orinoco 

 and the mountain chain of Caracas, or the pine forests of 

 Mexico. It is the co-existence of forms which may partially 

 replace each other, and their relative numbers and association, 

 which give rise either to the general impression of luxuriance 



* Ehrenberg, in the Annales des Sciences naturelles, i. xxi. pp. 387- 

 412 ; Humboldt, Asic centrcde, t. i. pp. 339-342, and t. iii. pp. 96-10L 



