FLOWERS AND INSECTS 



133 



Illustrations of this process may be taken from the flowers 

 already described in connection with the prevention of 

 self-pollination. 



In the flowers of the pea family, such as the rose acacia 

 (see Fig. 131), it will be 

 noticed that the stamens 

 and pistil are concealed 

 within the keel, which 

 forms the natural land- 

 ing place for the bees 

 which are used in pol- 

 lination. This keel is 

 so inserted that the 

 weight of the insect de- 

 presses it, and the tip 

 of the style comes in 

 contact with its body. 

 Not only does the 

 stigma strike the body, 

 but by the glancing 

 blow the surface of the 

 style is rubbed against 

 the insect, and on this 

 style, below the stigma, 

 the pollen has been de- 

 posited and is rubbed 

 off against the insect. 

 At the next flower 

 visited the stigma is 

 likely to strike the pol- 

 len obtained from the previous flower, and the style will 

 deposit a new supply of pollen. 



In the flower of the common flag (see Fig. 132) the nectar 

 is deposited in a pit at the bottom of the chamber formed 

 by each style and petal. In this chamber the stamen is 

 found, and more or less roofing it over is the flap, or shelf, 



Fig. 138. Flower of Cypripedwm, showing the 

 flap overhanging the opening of the pouch, 

 into which a bee is crowding its way. The 

 small figure to the right shows a side view of 

 the flap ; that to the left a view beneath the 

 flap, showing the two dark anthers, and be- 

 tween them, further down (forward), the 

 stigma surface. — After Gibson. 



