FERTILIZATION OF FLOWERS. 355 



For collecting pollen the bees make use of their legs, on which 

 special collecting brushes and baskets are formed by the stiff 

 hairs. The pollen is first moistened with honey to make it stick 

 together, and then picked up on the collecting brushes, placed 

 in the baskets on the hind legs and carried to the hive or nest. 



Insects commonly visit a large number of flowers of the same 

 kind in rapid succession, and, whether they intentionally collect 

 pollen for their own purposes or not, it is evident that, after each 

 visit to a flower containing ripe pollen grains, they will uninten- 

 tionally carry away some of these, accidentally attached to various 

 parts of the body. The pollen which is thus unconsciously 

 carried away is equally unconsciously deposited on the stigma of 

 the next flower visited, and thus cross-fertilization is effected. 

 It may, of course, happen sometimes that the pollen is deposited 

 on the wrong kind of flower, but that is of no consequence, for 

 pollen is, with rare exceptions, quite incapable of fertilizing 

 flowers of any but its own particular species. 



Under these circumstances it will obviously be advantageous 

 to a plant to make its flowers as attractive to insects as possible, 

 and, just as it is desirable for a nauseous insect to inform the 

 birds by means of warning colours of the fact of its unpalatability, 

 so also is it desirable for flowers which have honey to offer in 

 exchange for the service of pollination to make that fact known 

 to their insect visitors by means of brilliant colours and strong 

 scents. There can be no reasonable doubt that the colours serve 

 to attract the insects and to enable them to recognize the flowers 

 which they prefer, and that the same is true of the scents is very 

 clearly indicated by the fact that certain flowers, such as various 

 species of Arum and related genera, which are fertilized by 

 carrion-loving flies, have managed to perfume themselves in 

 accordance with the tastes of their visitors. 



It is also desirable to ensure, by means of mechanical arrange- 

 ments, that the insects shall not get their honey without paying 

 for it, that is to say, without effecting fertilization, and this end 

 is usually secured by concealing the honey at the bottom of a 

 long tube, in such a manner that the insect must brush against 

 the stamens and stigma before it can reach it. Sometimes, how- 

 ever, the insects become a little too clever for the flower and steal 

 the honey by biting a hole through the bottom of the tube with- 

 out ever touching the stamens or stigma at all. In this way the 

 red clover flowers are ^ften robbed of their honey by the humble 



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