232 TROPICAL NATURE, AND OTHER ESSAYS. 



Why Alpine Flowers are so Beautiful. The beauty 

 of alpine flowers is almost proverbial. It consists either 

 in the increased size of the individual flowers as com- 

 pared with the whole plant, in increased intensity of 

 colour, or in the massing of small flowers into dense 

 cushions of bright colour ; and it is only in the higher 

 Alps, above the limit of forests and upwards towards the 

 perpetual snow-line that these characteristics are fully 

 exhibited. This effort at conspicuousness under adverse 

 circumstances may be traced to the comparative scarcity 

 of winged insects in the higher regions, and to the 

 necessity for attracting them from a distance. Amid 

 the vast slopes of debris and the huge masses of rock so 

 prevalent in higher mountain regions, patches of intense 

 colour can alone make themselves visible and serve to 

 attract the wandering butterfly from the valleys. Mr. 

 Herman Muller's careful observations have shown, that in 

 the higher Alps bees and most other groups of winged 

 insects are almost wanting, while butterflies are tolerably 

 abundant ; and he has discovered, that in a number of 

 cases where a lowland flower is adapted to be fertilized by 

 bees, its alpine ally has had its structure so modified as 

 to be adapted for fertilization only by butterflies. 1 But 

 bees are always (in the temperate zone) far more abun- 

 dant than butterflies, and this will be another reason why 

 flowers specially adapted to be fertilized by the latter 

 should be rendered unusually conspicuous. We find, 

 accordingly, the yellow primrose of the plains replaced by 

 pink and magenta-coloured alpine species ; the straggling 

 wild pinks of the lowlands by the masses of large flowers 

 in such mountain species as Dianthus alpinus and D. 



1 Nature, vol. xi. pp. 32, 110. 



