FLOWERS AND INSECTS 



247 



the several stamens and the single carpel are in a cluster 

 enclosed in a boat-shaped structure (keel) formed by two 

 of the petals (Fig. 241). The stigma is at the summit of 

 the style and projects somewhat beyond the pollen sacs, 

 some of whose pollen lodges on a hairy zone on the 

 style below the stigma. While the stigma is not alto- 

 gether secure from receiving some pollen, the position 

 does not favor it. The 

 projecting keel is the nat- 

 ural landing place for a 

 bee visiting the flower; 

 and it is so inserted that 

 the weight of the insect 

 depresses it, and the stig- 

 ma comes in contact with 

 its body. Not only does 

 the stigma strike the 

 body, but by the glan- 

 cing blow the surface of 

 the style is rubbed against 

 the insect; and upon this 

 style, below the stigma, 

 the pollen has been shed 

 and is rubbed off against 

 the insect. At the next 

 flower visited the stigma 

 is likely to strike the pol- 

 len obtained from the pre- 

 vious flower, and the style 



will deposit a new supply of pollen. It is interesting to 

 press down slightly the keel of such a flower and see the 

 style apparently dart out. 



In the iris or common flag, each stamen is in a kind of 

 pocket between the petal and the petal-like style; while 

 the stigmatic surface is on the top of a flap or shelf which 

 17 



FIG. 242. Longitudinal section of flower of 

 iris, showing a single stamen between the 

 drooping petal and the petal-like style ; 

 the stigmatic shelf is seen above the 

 stamen, at the top of the style; the nectar 

 pit is at the junction of petal and stamen. 

 After GRAY. 



