Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/119

. IV. that the distal hinged portion of the labellum was of importance in the fertilisation of the flowers, I asked Mr. More to remove this part from some young flowers, and to mark them. He tried the experiment on eleven flowers, three of which did not produce seed-capsules; but this may have been accidental. Of the eight capsules which were produced, two contained about as many seeds as those from unmutilated flowers on the same plant; but six capsules contained much fewer seeds. Most of the seeds were well-formed. These experiments, as far as they go, support the view that the distal part of the labellum is of importance in causing insects to enter and leave the flowers in the best manner for their fertilisation.

Since the appearance of the first edition of this book, my son William has observed for me this Epipactis in the Isle of Wight. Hive-bees seem to be the chief agents in fertilisation; for he saw them visit about a score of flowers, and many had pollen-masses attached to their foreheads, just above the mandibles. I had supposed that insects always crawled into the flowers; but hive-bees are too large to do this; they always clung, whilst sucking the nectar, to the distal and hinged half of the labellum, which was thus pressed downwards. Owing to this part being elastic and tending to spring up, the bees, as they left the flowers, seemed to fly rather upwards; and this favoured, in the manner previously explained, the complete withdrawal of the pollen-masses, quite as well as if the insects had crawled, in an upward direction, out of the flower. Perhaps the upward movement may not be so necessary in all cases as I had supposed; for, judging from the manner in which the pollen-masses were attached to the hive-bees, the back part of their heads could hardly fail to press against and lift up the