296 DISTRIBUTION OF SWISS ALPINES 



Primula longiflora, All., and Phyteuma pauci- 

 florum, Linn., are rare plants found in the Valais, 

 Grisons, and Tessin. 



How can these inequalities of distribution be 

 explained? Some of the older observers attributed 

 the facts to the effect of soil or cHmate alone. There 

 is, however, little doubt that this explanation is 

 insufficient. A celebrated Swiss botanist, the late 

 Alphonse de Candolle of Geneva, has left us a more 

 plausible theory. 



It can scarcely be doubted, even by the most 

 sceptical, that the Alps were at one time more heavily 

 glaciated than they are at present. The retreat of 

 the glaciers, with certain exceptions, has been marked 

 even within the last few decades. The amount of 

 glaciation appears, however, to have been as unequal 

 in the past as it is at present, and it is to this fact 

 that De Candolle attributes the observed inequalities 

 of distribution among Alpine plants. The southern 

 chain of the Valais and the eastern Ehaetian Alps 

 appear to have been less glaciated than the central 

 Oberland region and northern Switzerland generally ; 

 ; and further, the glaciers there began to retreat earlier 

 ' than in the Oberland. The consequence has been, on 

 this theory, that the Valais and Grisons were being 

 colonised by Alpines, while the Bernese Alps remained 

 a vast waste of ice or snow.^ 



j; ^ According to Prof. Jaccard, the number of species to be found in 

 I any locality is directly proportional to tlie diversity of its ecological 

 '' formations. 



