IV 



ON PLANT LIFE 



127 



less. In the other two the anthers or cells pro- 

 ducing the pollen, which in most flowers form 

 together a round knob or 

 head at the top of the 

 stamen, are separated by 

 a long arm, which plays 

 on the top of the stamen 

 as on a hinge. Of these 

 two arms one hangs down 

 into the tube, closing the 

 passage, while the other 

 lies under the arched upper lip. When the 

 Bee pushes its proboscis down the tube (Fig. 11) 



Fig. 



Fig. 10. 



Fig. 11. 



it presses the lower arm to one side, and the 

 upper arm consequently descends, tapping the 



