MORE ABOUT POLLINATION 



313 



obtained by any visiting insect. Regular flowers whose 

 corollas form a tube are somewhat more select as to their 

 visitors ; only insects with elongated mouth parts are able 

 to reach the nectar without breaking the wall of the tube. 

 (See Figure 132.) Sometimes bees, wasps, or ants reach 



Fig. 133. — Pollination in Salvia. A, lengthwise section of the flower; s, the un- 

 ripe stigma ; a, the ripe anther ; the arrow points to a lower arm of the stamen ; 

 by pushing back this arm the visiting bee forces the anther down upon its own 

 back. B shows the position of the anther when the lower arm of the stamen is 

 pushed back. C shows a bee at work. D is an older flower in which the stigma, 

 now ripe, is ready in its turn to be brushed by the back of the bee. — ■ After Kerner 

 and Avebury. 



the nectar of such .flowers by biting holes through the 

 corolla tubes near the bottom. Such holes are often seen 

 in the corolla tubes of the trumpet creeper, a plant whose 

 flowers are frequently visited by humming birds. 



Flowers with zygomorphic corollas are, as a rule, depend- 

 ent for pollination upon certain kinds of insects, and it is 

 the bees upon which such dependence is principally placed. 

 Zygomorphic flowers are characteristic of the legumes (pea 



