rarrim] THE MECHANISMS OF FLOWERS. 81 
In many seasons with less favourable weather I have found 
LE. hiemalis (which I have immediately in front of my window, 
and can easily watch) not visited by insects at all, and yet bearing 
fruit, but more sparingly than when insect-visits have taken place. 
The reason of the smaller number of seeds is that, as in Ranun- 
culus and Caltha, self-fertilisation can only take place to a limited 
extent: for when I fertilised in my room, one flower with its own, 
and another with extraneous pollen, both produced seeds in equal 
abundance. 
f The species of Helleborus are proterogynous, according to 
_ Hildebrand (351). 
| Nigella arvensis, L.—The ectmenidooti flowers of this plant 
_ are provided with nectaries covered by movable lids, and are 
_ fertilised by bees. They have been fully described by Sprengel. 
4 Nigella damascena, L., is visited by Ceratina callosa, F. 3, and 
Prosopis signata, Nyl. g (Apide) (590, 1). 
13. AQUILEGIA VULGARIS, L.—The five sepals of the pendulous 
flower form broad blue expansions, which help to render it 
conspicuous. Each of the five petals is hollowed out from its 
insertion upwards to form a hollow spur 15 to 22 mm. long, whose 
i cup-shaped mouth is wide enough to admit the head of a humble- 
__ bee, and whose narrow tubular part curves inwards and downwards 
at its upper end. In this curved part is contained the honey, 
_ which is secreted by a fleshy thickening in the extreme point of 
_ the spur. Owing to its curvature the point of the spur is only 
_ 10 to17 mm. above the insertion of the petal. To reach the honey 
ina legitimate way, the bees hang on to the flowers below, grasping 
the base of the spur with their forelegs, and holding on with their 
_ mid and hindlegs to the column formed of the stamens and 
_ carpels, which projects perpendicularly or obliquely downwards 
from the centre of the flower; the head, meanwhile, is introduced 
_ into the aperture of the spur, whose outer wall its upper surface 
_ touches, and the end of the proboscis follows the curvature of the 
_ spur. Since bees very ‘easily bend the end of their proboscis 
_ downwards, but scarcely bend it voluntarily in the opposite direction, 
_ the position just described is the only one suitable for them to 
reach the honey. This position entails that in younger flowers 
_ the hinder and lower surface of the bee’s body touch the anthers, 
_ which closely surround the carpels and which are covered on their 
1 See also Kerner, No. 386, p. 101, for an account of the pits in NV, sativa and 
WN. elata. 
G 
