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 several 

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

 considered as such. The share taken by humming-birds in causing the 

 peculiarities of many American flowers can be ascertained only by careful 

 and critical investigations on the spot. Undoubtedly these brilliantly 

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

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

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

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

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

 Trinidad, Norantea guianensis resplendent with scarlet nectaries and with 

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

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

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

 in the summer, every day I could see the single indigenous species of 

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

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

 exclude visits to flowers that are differently coloured ; for the flowers 

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

 colour, 



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

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

 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 seeing 

 the " Flame of the Forest " (Poinciana regia) in a blaze of blossom would, after 

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

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

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

 flowers and are commonly cultivated in warm countries as ornamental plants 

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

 American than in the Malayan flora. 



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

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

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

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

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

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

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

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

 Bromeliaceae with coloured bracts, so far as I have seen them in their native 

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

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

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



