14 INTRODUCTORY 



flowers, borne either on one plant or on two different 

 plants. In a very large number of cases, the male 

 and female organs, especially where they occur in the 

 same flower (the so-called hermaphrodite flowers), are 

 enclosed in a floral envelope or perianth, often 

 differentiated into an outer series, the calyx, composed 

 of sepals, and an inner series, the corolla, composed of 

 petals. The floral envelope may, however, be very 

 poorly developed in some flowers. It plays many 

 different parts in various plants, as we shall see. It 

 serves partly to protect the young developing sexual 

 organs in the unopened flower-bud, and in many cases 

 it also furnishes a conspicuous advertisement for the 

 allurement of insects, which carry the pollen of one 

 plant to the female organs of another, and so eff'ect 

 cross-pollination.^ 



It will be our object in the present volume to 

 bear constantly in mind the influence of the severe 

 climatic conditions of the Alpine world on the vital 

 processes of the plant, both those relating to existence 

 and to reproduction. We shall find that many of the 

 peculiarities of Alpines are alone intelligible from this, 

 the biological standpoint, which is entirely different 

 from that of the systematic or descriptive Botanist. 



We may illustrate these principles by reference to 

 the two national flowers of Switzerland : the Edelweiss 

 and the Alpenroses. Both will be found to show 

 interesting adaptations to their special surroundings. 



^ Further information on the structure of the flower will be found 

 in Appendix II. 



