. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. LEGUMINOSAE 289 states that the nectar is concealed in the base of a tube 9-10 mm. long, formed bv fusion of the nine lower filaments with the claws of the petals. The upper free stamen lies on one side of the flower, so that the whole of the cleft in the staminal tube serves as a nectar passage. When a bee thrusts its proboscis under the vexillum towards the nectar, it holds on with its fore-legs to the alae, which are united with the carina, while its othe
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. LEGUMINOSAE 289 states that the nectar is concealed in the base of a tube 9-10 mm. long, formed bv fusion of the nine lower filaments with the claws of the petals. The upper free stamen lies on one side of the flower, so that the whole of the cleft in the staminal tube serves as a nectar passage. When a bee thrusts its proboscis under the vexillum towards the nectar, it holds on with its fore-legs to the alae, which are united with the carina, while its other two pairs of legs are supported by deeper parts of the capitulum. The pressure exerted depresses the carina and alae, so that the stigma protrudes, to be immediately followed by the upwardly dehisced anthers, which press against the under-side of the bee's head. The stigma consequently receives pollen brought from another flower, and this is replaced by a fresh supply. Cross-pollina- tion is thus assured. Self-pollination may also take place when the head of the bee is withdrawn, but Darwin says that this is ineffective (though Kerner is of the opposite opinion), and is rendered inoperative by the previously effected cross- pollination. The return of the parts to their original position, after re- moval of the pressure exerted by the insect, is brought about by the intrinsic elasticity of the base of the carina. The thin easily rotated claws of the alae separate from the common tube, and the two large vesicular processes of these petals grasp the reproductive column from above, their elasticity keeping the stamens, pistil, and the parts which enclose them, in their proper positions. The staminal tube is continued into free, stiff, upwardly curved fila- ments, somewhat thickened at the end; the style curves upwards between them in such a way that the stigma projects above the anthers to some extent. In order to reach the nectar legitimately, an insect must have a proboscis of
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