200 THE FERTILISATION OF FLOWERS. [PART IIT. 
of its base it bears a flattened triangular process (vp. C! C?) which 
fits exactly over the nectaries (1) and closes them with considerable 
firmness. <A bee visiting the flower can only obtain the honey by 
using the vexillum as a long lever to raise up this lid; and to do 
this it must insert its head beneath the vexillum, and consequently 
effect cross-fertilisation. . 
On the Alps I observed various bees cross-fertilising the plant, 
and also numerous Lepidoptera which visited the flowers but only 
effected cross-fertilisation occasionally (609). 
Fic. 67.—Onobrychis sativa, Lam, 
1.—Flower, from below (x 8), 
2.—Ditto, after removal of the vexillum and the upper half of the calyx, from above. 
3.—Essential organs, from the side (x 7). 
a, calyx; b, carina; c, ala; d, vexillum, pale red with darker lines (pathjinders) ; e, claw of ala ; 
f. coherent filaments ; g, free stamen; h, entrance to honey; i, cleft of carina, through which the 
anthers and stigma emerge. 
116. ONOBRYCHIS SATIVA, Lam.—The flower has the same 
simple structure as we have studied in the case of Melilotus and 
Trifolium : when the carina is depressed, the stigma and the anthers 
(which dehisced in the bud) emerge, and when the pressure is 
removed the carina springs up and again incloses these organs. 
The arrangement in this case is still simpler than in the two 
above-named genera, since the carina performs by itself the fune- 
tions which the alee formerly shared with it; for the ale are very 
much reduced, only covering the claw of the carina, and serving 
to prevent or to render difficult the removal of honey at either 
