. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 420 ANGIOSPERMAE—MONOCOTYLEDONES 2652. C. Calceolus L. (Herm. MuUer, ' Fertlsn.,' p. 539 ; Baxter, ' Fertlzn. of Cypripedium'; Webster, Trans. Bot. Soc, Edinburgh, xvi, 1886, pp. 357-60; Darwin, op. cit., p. 226 ; Kerner, ' Nat. Hist. PI.,' Eng. Ed. i, II, pp. 245, 249.)—In flowers of this species the slightly contracted labellum is yellow in colour, and the rest of the perianth leaves purple. This colouring and an odour of nectar attract small bees of the g
. Handbook of flower pollination : based upon Hermann Mu?ller's work 'The fertilisation of flowers by insects' . Fertilization of plants. 420 ANGIOSPERMAE—MONOCOTYLEDONES 2652. C. Calceolus L. (Herm. MuUer, ' Fertlsn.,' p. 539 ; Baxter, ' Fertlzn. of Cypripedium'; Webster, Trans. Bot. Soc, Edinburgh, xvi, 1886, pp. 357-60; Darwin, op. cit., p. 226 ; Kerner, ' Nat. Hist. PI.,' Eng. Ed. i, II, pp. 245, 249.)—In flowers of this species the slightly contracted labellum is yellow in colour, and the rest of the perianth leaves purple. This colouring and an odour of nectar attract small bees of the genus Andrena, which creep into the dilated labellum, finding on its under-side juicy hairs which sometimes perhaps also secrete minute drops of nectar; these they lick or gnaw. There are three openings serving as entrances to the cavity of the labellum, one to the right and one to the left of the column, and a wider, oval median one in front of it. Insects choose the latter exclusively as an entrance. When small bees have satisfied themselves in the cavity, they try to get out of it again; the walls. Fig. 38c). Cypripcdijtm Calceolus, L, (after Hcrm. Miiller). (i) Flower, with its parts in the natural position, seen in front and from above. (2) Do., in longitudinal section, after removal of the lateral petals : the labellum is bent slightly downwards, to show the opening ex clearly. (3) The reproductive organs from below. aa, anthers; a\ vestigial anther; ex, exit; *, entrance; ov, ovary; pp, lateral petals; p\ labellum ; s, sepals; st, stigma. of their prison, however, are so strongly arched that they cannot escape by the entrance, but finally squeeze themselves, after having crept under the stigma, through one of the two narrow lateral openings. In doing so they brush with one shoulder or the other against the soft, viscous pollen of the anther which forms the inner boundary of the selected exit. In a second flower they deposit the pollen on the broad, rough stigma in cre
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