420 



ANGIOSPERMAEMONOCOTYLEDONES 



2652. C. Calceolus L. (Herm. Muller, ' Fertlsn.,' p. 539; Baxter, 'Fertlzn. 

 of Cypripedium'; Webster, Trans. Bot. Soc, Edinburgh, xvi, 1886, pp. 357-60; 

 Darwin, op. cit., p. 226 ; Kemer, ' Nat. Hist. PI.,' Eng. Ed. i, II, pp. 245, 249.) In 

 flowers of this species the slighdy 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. 389. Cypripedium Calceolus, L. (after Herm. MuUer). (i) Flower, with iu part8 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, a a, anthers; ', vestigial anther; ex, exit; i, entrance; <w, 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 creeping under it, while in creeping out of the cavity theyJ 

 take up fresh pollen, so that crossing is regularly effected. The juicy hairs at thej 

 base of the labellum make it easier for them to creep out, as they use them 

 a climbing surface {cf. Vol. I, p. 131). 



Visitors. Herm. MOller gives the following list: 

 Five bees species of Andrena i.e. i. A. albicans Milll. 5; 2. A. atriceps K. 

 (=A. tibialis iST.) ; 3. A. fulvicrus A'. 5; 4. A. nigroaenea K. ^\ 5. A. pratensi^ 



