8 INTRODUCTORY 



higher the centre chosen, the more interesting the 

 flora. 



With regard to the number of species of Flowering 

 Plants (Angiosperms) found within the Alpine zone, 

 estimates naturally vary. Ball calculated that in the 

 Alpine region of the whole chain of the Alps, 1,117 

 species are found, belonging to 279 genera and 60 

 natural orders. In the corresponding zone of the 

 Swiss Alps, I estimate the number of species as 

 about 900 out of a total of 2,350 Swiss Angiosperms. 

 Of these, some 300 are confined entirely to the Alpine 

 zone, while roughly 250 are also lowland plants, and 

 in many cases members of the British flora. The 

 rest occur both in the Alpine and Subalpine regions. 



We now pass to some consideration of the 

 difficulties which a plant has to overcome in order 

 to survive the rigours of an Alpine climate. If we 

 are to understand and appreciate these difficulties, 

 we must arrive at some clear conception of the 

 internal economy of the plant itself. The plant has 

 two duties to perform. A duty to itself, to maintain 

 its own existence, and a duty to the next generation 

 — reproduction. We will now briefly discuss the first 

 of these. 



The plant is a living being which may be likened 

 to a complicated steam engine or other piece of 

 machinery in motion. It is fashioned for one end 

 alone — the existence of the species. All plants are 

 built up of an enormous number of very small units, 

 termed cells. The cells diff'er very much in form, 



