_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 Umbelliferæ, or such elegant bunches as those of the lilac, laburnum, horse chestnut, and wistaria. In other cases minute flowers are gathered into dense heads, as with _Globularia_, _Jasione_, clover, and all the Compositæ; and among the latter the outer flowers are often developed into a ray, as in the sunflowers, the daisies, and the asters, forming a star-like 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 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. Hermann Müller’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.[23] But bees are always (in the temperate zone) far more abundant 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. glacialis_; the saxifrages of the high Alps with bunches of flowers a foot long as in _Saxifraga longifolia_ and _S. cotyledon_, or forming spreading masses of flowers as in _S. oppositifolia_; while the soapworts, silenes, and louseworts are equally superior to the allied species of the plains. [23] _Nature_, vol. xi. pp. 32, 110.