INSECT FERTILIZATION OF FLOWERS. 



603 



bee the arrangements are similar to those just deseribed, but the hairs 

 of the tarsus are much better adapted to their purpose (Fig. 19). They 

 are disposed in eight or nine rows, while in the humble-bee they are 

 distributed irregularly. By this regularity of arrangement the honey- 

 bees are enabled to brush the pollen from the anthers far more effect- 



Fig. 17. Fig. 1?. Fig. 19. 



Hind-Legs op Bees, showing structures for collecting pollen. Fig. 17. Hairy -bee, four times 

 enlarged. Fig. 18. Humble-bee, four times enlarged. Fig. 19. Honey-bee, five times en- 

 larged, i?, trochanter; S, femur; T, tibia; A, prickles on tibia; P, tarsus (polleu-brush) ; F, 

 other segments of the foot ; K, claws. 



ually. The pollen, once removed from the antlers, is next transferred 

 to the hairs, or to the surface of the tibia, to which, being viscid, it 

 readily adheres. After the process of collecting has been carried on 

 for some time, the pollen forms thick yellow masses, which completely 

 envelop the legs. Laden with the fruits of its toil, the insect wings 

 its way homeward, and deposits them in the bee-hive. 



While our native flowers are many of them entirely dependent on 

 insects for the transference of pollen, the process of cross-fertilization 

 is, in many tropical species, always effected by birds, which visit the 

 flowers on account of their nectar. 



In America the humming-birds (Trochilidce, Figs. 20-22) and in 

 Africa the honey-eaters ( Cinnyridce) are the great promoters of cross- 

 fertilization. 



The honey-birds are found in the tropical regions of Africa, Asia, 

 and Australia, while the humming-birds belong to tropical and South 

 America. The former suck the honey with their long, tubular tongue, 

 which is brush-like at the tip. Their relations to flowers have not yet 

 been sufficiently investigated, but a good deal is known respecting 

 those of humming-birds. 



The humming-birds are small (the largest species attaining to about 

 the size of a swallow, the smallest not much larger than a humble-bee) 

 and of delicate structure. They are famed for their magnificent plum- 

 age, which almost always displays metallic tints. Their flight does 



