THE ALPINE FAUNA. 341 



the botanical aspect of the Alpine problem might not 

 be out of place. It will enable us to judge which of 

 the views indicated is the more probable, and will 

 add to the interest which may have been aroused by 

 the perusal of this sketch of the fauna of the Alps. 

 Very much the same train of argument was applied 

 as to the course of events in the formation of the 

 Alpine flora as in the case of the fauna. The plants 

 were all supposed to have been killed or driven away 

 by the arctic temperature of the Glacial period, and 

 their place taken by new migrants from the north or 

 east when the climate ameliorated. 



Professor Engler, one of the highest living 

 authorities on the geographical distribution of plants, 

 is of opinion (p. 102) that a large number of the 

 indigenous Alpine species did not originate till after 

 the close of the Glacial period, because so many of 

 them are absent from the Sierra Nevada in Spain, 

 where the condition for their well-being exists, 

 while many have evidently spread from the 

 Alps to the Carpathian Mountains and to the 

 Pyrenees. He does not believe that a glacial flora 

 could 'have existed in the plain between the Sierra 

 Nevada and the Pyrenees during the Glacial period 

 (p. 109). In speaking of the Caucasus, Professor 

 Engler informs us (p. 117) that a good many species 

 which do not occur in the Alps reached these 

 mountains from Siberia. Apart from the northern 

 glacial plants, the Caucasus has only few species in 

 common with the Alps, more with the Balkan moun- 



