286 TIEWS, &C. PHYSIOGNOMY OF PLANTS. 



these families are for the most part different, lead us into that 

 mysterious obscurity which envelopes everything connected 

 with the fixing of organic types in the different species of 

 animals and plants, and with all that refers to formation and 

 development. I will take as examples two neighbour- 

 ing countries France and Germany which have both been 

 long since explored. In France many species of Gramineae, 

 Umbelliferse, Cruciferse, Composite, Leguminosae, and Labiataa 

 are wanting, which are some of the commonest in Germany, 

 and yet the ratios of these six large families are almost iden- 

 tical in both countries. Their relations, which I here give, 

 are as follows : 



Families. Germany. France. 



Gramme* .... yj .... .... iV 



Umbellifera lV ^ 



Cruciferee -j^ .... .... -^ 



Composite .... -g- .... .... y 



Leguminosie .... -fy iV 



Labiate ^ ^ 



This correspondence in the number of species of one 

 family compared to the whole mass of the phanero- 

 gamia of Germany and France would not exist, if the 

 absent German species were not replaced in France by other 

 types of the same families. Those who delight in con- 

 jectures respecting the gradual transformation of species, 

 and who regard the different parrots, peculiar to islands 

 situated near each other, as merely transformed species, 

 will ascribe the remarkable uniformity presented by the 

 above numerical ratios to a migration of the same species, 

 which having been altered by climatic influences, continuing 

 for thousands of years, appear to replace each other. But 

 why have our common Heath, (Calluna vulgaris,) and our 

 Oaks not penetrated to the east of the Ural Mountains, and 

 passed from Europe to northern Asia? Why is there no 

 species of the genus Rosa in the southern, and scarcely any 

 Calceolaria in the northern hemisphere? These are points 

 that cannot be explained by peculiarities of temperature. 

 The present distribution of forms (fixed forms of organization) 

 is no more explained by thermal relations alone, than by the 



