vi COLOURS OF PLANTS 403 



Miiller to be fertilised by the humming-bird hawk moth, 

 which flies in the morning and afternoon, when the colours of 

 this flower, exposed to the nearly horizontal rays of the sun, 

 glow with brilliancy, and when it also becomes very sweet- 

 scented. 



Attractive Grouping of Flowers 



To the same need of conspicuousness the combination of 

 so many individually small flowers into heads and bunches is 

 probably due, producing such broad masses as those of the 

 elder, the guelder-rose, and most of the Umbelliferae, or such 

 elegant bunches as those of the lilac, laburnum, horse chest- 

 nut, and wistaria. In other cases minute flowers are gathered 

 into dense heads, as with Globularia, Jasione, clover, and all 

 the Composite ; and among the latter the outer flowers are 

 often developed into a ray, as in the sunflowers, the daisies, 

 and the asters, forming a starlike compound flower, which is 

 itself often produced in immense profusion. 



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 compared 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 dis- 

 tance. 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 

 Miiller'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 fertilised by bees, its Alpine ally has had its 

 structure so modified as to be adapted for fertilisation only 



