6 INTRODUCTORY 



zones : a lower, extending to the limit of deciduous ^ 

 trees ; and an upper, including all above this limit, 

 except a glacial region, where the soil is only free from 

 snow for two or three months in summer. This Glacial 

 or High Alpine region may well be distinguished as a 

 separate zone. 



Prof. Schroeter has recently published a com- 

 parative table showing how no less than twenty-five 

 botanists, between 1808 and 1904, have attempted to 

 subdivide Swiss vegetation in regard to altitude. No 

 two schemes agree even remotely ; and this diversity of 

 opinion well illustrates the impossibility of attempting 

 to define zones of altitude at all rigidly in regard to 

 vegetation. 



The altitude of 5,000 feet, which we will, then, take 

 as the mean lower limit of the Alpine zone for 

 Switzerland generally, is as natural a dividing line as 

 can be found. Not only does it indicate the average 

 lower limit of the Coniferous forests, but at this 

 height all the physical conditions which we term 

 Alpine — such as shortness of the flowering season and 

 intensity of the illumination — are typically in force. 

 Further, the majority of the plants flourishing at or 

 above this elevation, possess all those peculiarities 

 of architecture, or, as the botanist terms it, " habit," 

 which we associate especially with Alpine plants. 

 Biologically, then, these plants are Alpine, as well as by 



' Trees wHch slied their leaves in autumn. For this and other 

 technical terms, see Appendix I., p. 307. The Conifers, except the 

 Larch, are all evergreen. 



