42 



ANGIOSPERMAE—DICOTYLEDONES 



i8. Aquilegia Toum. 



Protandrous humble-bee flowers. The blossoms are rendered conspicuous by 

 the brightly coloured sepals and petals, and the stamens and carpels project from 

 among them like a yellow central column. Nectar is secreted and concealed at 

 the bottom of the spurs of the petals. 



go. A. vulgaris L. (Sprengel, 'Entd. Geh.,' pp. 279-80; Herm. Miilier, 

 ' Fertilisation,' pp. 81-2 ; Beyer, 'D. spont. Bewegungen d. Staubgefasse u. Stempel'; 

 Schulz, 'Beitrage'; Kirchner, 'Flora v. Stuttgart.,' p. 273; Knuth, ' Weit. Beob. u. 

 Bl. u. Insekt. a. d. nordfr. Ins.,' p. 230, ' Blutenbiol. Beob. a. d. Ins. Rugen.') — The 

 violet-blue (rarely pink or white) flowers are pendulous, so that the nectar secreted in 

 the ends of the spurs of the petals is protected from rain. The spurs are 15-22 mm. 

 long, and their funnel-like openings are wide enough to readily accommodate the 

 head of a humble-bee. The much narrower terminal part of the spur curves inwards 

 and downwards, and conceals the nectar, which is secreted by a fleshy thickening at 

 the extreme tip. Humble-bees — which possess a proboscis long enough to reach 

 the nectar in the legitimate way — cling to the flowers from below, holding on to 



Fig. 15. AquiUgia vulgaris, L. (From nature : the front petal and two sepals have been removed.) 



A. Flower in the first (male) condition : most of the anthers {a}) have already dehisced, a few of them (a') 

 are still immature, with their short filaments still directed upwards. The stigTiias (j) are still immature. 



B. Flower in the second (bisexual) condition ; all the anthers (a) have dehisced, and the stigmas (j) are 

 mature, w, nectary. 



the base of the spur with the fore-legs, and to the stamens and carpels with the 

 other two pairs of legs, and pushing the head into the spurs. In so doing the under- 

 side of the abdomen comes into contact — in the younger flowers — with the pollen- 

 covered anthers, which closely surround the pistil. In older flowers the same region 

 of the body touches the somewhat spreading stigmas which project from among 

 the stamens, so that cross-pollination is necessarily eff"ected. Should insect-visits 

 fail, automatic self-pollination readily takes place, for the carpels grow down in 

 the middle of the stamens, and by elongation of the styles the stigmas ultimately 

 reach a lower level than the anthers. 



Visitors. — The usual pollinator is the garden humble-bee (Bombus hortorum Z.), 

 the long (19-21 mm.) proboscis of which easily reaches to the tip of the spur. It 

 is the most frequent visitor of the columbine : I observed it in Schleswig-Holstein, 

 Mecklenburg, Thuringia, North Pomerania, Riigen, the North Frisian islands, and 



