MOVEMENTS OE FLORAL ORGANS 



431 



In some flowers whose stamens perform rapid movements 

 when an insect enters, it is easy to see how directly useful the 

 motion of the stamens is in securing cross pollination. The 

 stamens of the laurel (Kalmia) are held in a bent position by 

 the expanded corolla, and when liberated by a touch throw little 

 masses of pollen, with a quick jerk, against the body of the 

 visiting insect. Barberry flowers have filaments which are sen- 

 sitive on the inner side near the base, and when touched make 

 the anther spring up against the visitor and dust him with 

 pollen. The common garden sage matures its anthers earlier 

 than its stigmas. In Fig. 331, A, the young flower is seen, vis- 

 ited by a bee, and one anther, 

 an, is shown pressed closely 

 against the side of the bee's 

 abdomen. The stigma, st, is 



p 



f 



a 



a' 



FIG. 332. Flower and stamens of common sage 



A, p, stigma; a, anthers. 13, the two stamens in ordinary position; /, filaments; 

 m, connective (joining anther cells) ; a, ', anther cells. O, the anthers and 

 connectives bent into a horizontal position by an insect pushing against .- 

 After Lubbock. 



hidden within the upper lip of the corolla, In B, an older 

 flower, the anthers have withered and the stigma is now low- 

 ered so as to brush against the bodv of anv bee which mav 



O v v ** 



enter. A little study of Fig. 332 will make clear the way 

 in which the anthers are hinged, so that a bee striking the 

 empty or barren anther lobes, a, knocks the pollen-bearing 

 lobes, a 1 , into a horizontal position, so that they will lie closely 

 pressed against both sides of its abdomen. Many stigmas, as 

 those of catalpa and trumpet creeper, close as soon as they 

 are pollinated. 



