HERBACEOUS AND WOODY DICOTYLEDONS 399 



Anther 



AQUILEGIA (COLUMBINE) 



In the columbines the flowers are very highly modified and 

 irregular, the five petals being developed into long spurs with 

 nectaries at the tips. The flowers are pendulous, and the nectar 

 secreted in the end of the spur is thus protected from rain. They 

 are pollinated by bumblebees, which possess a proboscis long 

 enough to penetrate to the nectar at the base of the spur, which 

 may be from 15 to 

 20 mm. in length 

 (Fig. 250, a). 



The following 

 account of the 

 pollination of 

 Aquilegia vulga- 

 m, taken from 

 Knu th's Hand- 

 book, will serve 



to indicate the c "'^Stigmas 



details ill Other FIG. 250. Flowers of the columbine (Aquilegia) 



species. " Bum- 

 blebees, which 

 possess a probos- 

 cis long enough to reach the nectar in the legitimate way, cling 

 to the flowers from below, holding 011 to the base of the spur 

 with the forelegs and pushing the head into the spur. In so 

 doing the underside of the abdomen comes in contact, in the 

 young flowers, with the pollen-covered anthers which surround 

 the pistil (Fig. 250, I). In older flowers (c) the same region of 

 the body touches the somewhat spreading stigmas which project 

 from among the stamens, so that cross-pollination is necessarily 

 effected. Should insect visits fail, automatic self-pollination 

 readily takes place, for the carpels (pistils) grow down in the 

 middle of the stamens, and by elongation of the style the stigmas 

 ultimately reach a lower level than the anthers." Other mem- 

 bers of the Ranunculaceae are also highly modified for securing 

 cross-pollination by insects. 



ntfier 



a, single flower; 6, young flower with anthers surrounding 

 the stigmas; c, older flower with pollen^shed and stigmas 

 protruding. FromKnuth's "Handbook of Flower Pollination " 



