Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/121

. IV. firmly united to the basal portion (fig. 16), so that it is not flexible and elastic; it apparently serves only as a landing-place for insects. The fertilisation of this species depends simply on an insect striking in an upward and backward direction the highly-protuberant rostellum, which it would be apt to do when retreating from the flower after having sucked the copious nectar

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Flower viewed sideways, with all the sepals and petals removed, except the labellum.

in the cup of the labellum. Apparently it is not at all necessary that the insect should push upwards the blunt upper end of the anther; at least I found that the pollinia could be removed easily by simply dragging off the cap of the rostellum in an upward or backward direction.

As some plants grew close to my house, I have been able to observe here and elsewhere their manner of fertilisation during several years. Although hive-bees and humble-bees of many kinds were constantly flying over the plants, I never saw a bee or any Dipterous insect visit the flowers; but in Germany Sprengel caught a fly with the pollinia of this plant attached to its back. On the other hand I have repeatedly