Page:Popular Science Monthly Volume 27.djvu/623

 the arrangements are similar to those just deseribeddescribed [sic], 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 effectually.

 showing structures for collecting pollen. Fig. 17.—Hairy-bee, four times enlarged. four times enlarged. five times enlarged, R, trochanter; S, femur; T, tibia; A, prickles on tibia; P, tarsus (pollen-brush); F, other segments of the foot; K, claws.

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 (Trochilidæ, Figs. 20-22) and in Africa the honey-eaters (Cinnyridæ) 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 plumage, which almost always displays metallic tints. Their flight does