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A TEXTBOOK OF THEORETICAL BOTANY 



flowers. Some blue Butterflies, on the other hand, select blue flowers. This 

 selectivity, even if it be only partial, may be related to another form of 

 attraction which is reputed to occur among Orchids, namely that the 

 labellum of the flower in such species as the Bee and the Spider Orchids 

 resemble a female insect of a species frequenting the flower, which suggests 

 that the attraction is sexual and that the insect is deceived by the resemblance. 

 So far as the Bee Orchid is concerned the suggestion can scarcely hold 

 good, since the flowers are habitually self-pollinated and are rarely visited. 

 It must not be overlooked that the insect has an interest to be served 

 in visiting a flower and that it will prefer those flowers that best suit its 

 size and capabilities, i.e., with regard to strength and length of tongue. 

 Such flowers, moreover, are less likely to have been visited and emptied 

 by other types of insects with different capabilities. Butterflies, which 

 have longer probosces than has any bee, prefer flowers with unusually 

 long or narrow floral tubes, in the frequentation of which they have a 



Fig. 1206. — Lilium philadelphicum. Flowers visited by a large 

 moth. The wings gather pollen from the freely suspended 

 anthers. Later this may be transferred to the stigma of an 

 older flow^er. The stigma is presented laterally by the 

 bending of the style. {After Dodel-Pori.) 



