PLANTS AT GREAT ELEVATIONS 175 



which are of rare or local occurrence, and are only 

 exceptionally met with at lower elevations. 



Heer found that ])etween 8,580 and 9,135 feet, 336 

 species occur in Switzerland as a whole, 294 in 

 Canton Grisons, 206 in Canton Valais, and 150 in 

 Canton Berne. As we ascend, the numbers gradually 

 decrease; at an elevation of about 10,200 feet, the 

 figures were 120, 32, 118, and 17 respectively; at 

 11,260 feet the number of species sank to 13, 4, 18, 

 and 6, while above 12,870 feet only 6 species occur in 

 the whole of Switzerland, none in the Grisons, 2 

 in the Valais, and 5 in Canton Berne. Thus the 

 Valais is much richer in High Alpine species, and 

 the Bernese Oberland much poorer, than any other 

 district in Switzerland. 



These figures give only an approximate result, for 

 estimates of the number of species in any district 

 difi'er according as the author regards certain plants 

 as distinct species or only as varieties — a question 

 which is always one of great difficulty, and 

 quite impossible to settle, for variation is character- 

 istic of plants as of animals. But whether we regard 

 Heer's figures as rather too high or too low is 

 immaterial. The important point is, that of 336 

 species occurring at about 8,600 feet, a large number 

 consist of plants common in the lower Alpine region, 

 while others are what we will term High Alpines, and 

 are almost unknown in the lower zone. 



Schroeter has made an analysis of tht^ flora 

 known to occur at, and above, 10,725 feet (- 3,250 



