LETTING THE BEES DO THEIR WORK 



the stigma only after the pollen has been dis- 

 charged — an expedient which, as we have seen, is 

 very commonly resorted to by other species of 

 plants, including the lilies. 



The Spanish broom (Spartium junceum) is a 

 typical butterfly-like flower, that, in common with 

 others of the same family, has developed a peculiar 

 mechanism to bring about cross-poUenation. The 

 two lower petals are joined together into a keel- 

 shaped structure that connects the stamens and 

 pistils. The other three petals are more enlarged, 

 and are spread to make a more effective advertise- 

 ment, challenging the attention of insects. The 

 visiting bee naturally alights upon the projecting 

 keel. The weight of its body presses this down- 

 ward and the stamens and pistils, by a spring-like 

 action, are thrust out against the body of the 

 insect, scattering the pollen freely. 



Thus the stigma may become covered with 

 pollen that the bee has received from some other 

 flower while the anthers supply a new coat of 

 pollen for future distribution. 



Still a different arrangement is that of the 

 common iris. Here the anthers lie in a fold of 

 the large petal-like branches of the style. The 

 stigmatic surface is confined to a little crescent- 

 shaped patch near the tip of the style-branches, 

 and is protected by a thin, sack-like shield. The 



[217] 



