FLORAL MECHANISMS 



101 



anthers arranged close about the pistil to hold the 

 pollen and deliver it at the moment it is called for. 

 The figure shows a section of the pansy with the 

 stamens clasping the style, and the anthers, which 

 open inward, shedding their pollen. The stigma 

 protrudes and opens like the tip of an elephant's 

 trunk, with two small lips. Now, supposing the 

 bee arrives with pollen on his head and back. He 

 is sure to deposit some of it upon the stigma, then, 

 in reaching for nectar, he 

 will disturb the position of 

 the stamens, and thus set 

 free fresh pollen and re- 

 ceive a shower of it on his 

 head and back. Now he 

 backs out and we might 

 expect him to leave some 

 of this fresh pollen on the 

 stigma; but the lower lip of the latter closes up 

 over his head, and self-fertilisation is thus pre- 

 vented, just as is the case in the iris. 



It is amusing to notice that the bumblebees and 

 honey-bees, habitual visitors, usually alight upon 

 the broad lower petal, then whirl around to tlie 

 upper petals, with their heads downward, this re- 

 versed position giving them better access to the 

 nectar-well within. 



PANSY 



