122 



THE FACTORS [Part I 



communications of F. Muller, the knowledge of humming-bird flowers 

 has not made any considerable progress, for the surmises of severa' 

 biologists formed far away from the home of humming-birds cannot be 

 considered as such. The share taken bj- humming-birds in causing thf 

 peculiarities of many American flowers can be ascertained only by carefu 

 and critical investigations on the spot. Undoubtedly these brilliantlj 

 coloured pollinators show a preference for red, especially for fiery rec 

 colours ; in regions where humming-birds abound, for instance th( 

 Antilles, I have rarely seen a woody plant resplendent in the sun wit! 

 the beauty of its red flowers without also being able to detect, with 

 little patience, humming-birds on it. I vividly remember having seen, ii 

 Trinidad, Norantea guianensis resplendent with scarlet nectaries and witl 

 humming-birds swarming round it. I have even observed these visitor. 

 on the peculiar, large, deep carmine flowers of Couroupita guianensis 

 In the garden of a house on the coast of Massachusetts, where I livec 

 in the summer, every day I could See the single indigenous species o 

 humming-bird (Trochilus colubris) frequenting the deep carmine flower 

 of a shrub of Weigela. This preference for red does not, howevei 

 exclude visits to flowers that are dift'erently coloured ; for the flower 

 of the species of Marcgravia that I know are of a dull brownisl 

 colour. 



Kerner endeavours to establish an essential connexion between, on the on 

 hand, the wealth of the American flora in plants with red blossoms, and on th 

 other, the presence of humming-birds. But what is the nature of this wealth 

 Certainly an uninitiated person landing at a tropical American port and seein 

 the '• Flame of the Forest " (Poinciana regia) in a blaze of blossom would, afte 

 a well-known example, be inclined to conclude that in tropical America th 

 trees have red flowers. But this most brilliant of all red-flowered trees is <' 

 East Indian origin, as are many other plants which make a scarlet display • 

 flowers and are commonly cultivated in warm countries as ornamental plant 

 I did not receive the impression that the red colour is more prominent in ti. 

 American than in the Malayan flora. 



Since sun-birds, which live in the greatest part of Africa, in tropical Asia, ar 

 in Australia, have also proved to be flower-pollinators and have a similar prefereni 

 for red tints, the question at any rate may be asked, whether the actually great. 

 wealth in bright red flowers and bracts, that distinguishes the warm zone fro 

 the north temperate zone, is connected with ornithophily. To the flowers th 

 are so distinguished belong, in America, among others, those of numeroi 

 Bromeliaceae, especially species of Aechmea and Vriesea ; in the Malay Archipelag 

 the Zingiberaceae. I have never seen any birds close to these flowers. Tl 

 Bromeliaceae w-ith coloured bracts, so far as I have seen them in their nati 

 habitats, live only in shady places, where the sun-loving humming-birds a 

 seldom seen, and the Malayan Zingiberaceae do not appear outside the deepe 

 forest shade, where sun-birds would be sought for in vain. 



