Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/80

60 easily pushed away, and answers to the pouch in Orchis. The whole upper part of the helmet answers to the minute oval bit of membrane to which the caudicle of Orchis is attached and which in Ophrys is larger and convex. When the lower part of the helmet is moved by any pointed object, the point readily slips into its hollow base, and is there held so firmly by the viscid matter, that the whole helmet appears adapted to stick to some prominent part of an insect's body. The caudicle is short and very elastic; it is attached not to the apex of the helmet, but to the hinder end; if it had been attached to the apex, the point of attachment would have been freely exposed to the air and not kept damp; and then the pollinium when removed from its cell would not have been quickly depressed.

This movement is well marked, and serves to bring the end of the pollen-mass into a proper position for striking the stigma. The two viscid discs stand wide apart. There are two transverse stigmatic surfaces, meeting by their points in the middle; but the broad part of each lies directly beneath each disc. The labellum is remarkable from not differing much in shape from the two upper petals, and from not always occupying the same position in reference to the axis of the plant, owing to the ovarium being more or less twisted. This state of the labellum is intelligible, for as we shall see, it does not serve as a landing-place for insects. It is upturned, and together with the two other petals makes the whole flower in some degree tubular. At its base there is a hollow so deep as almost to deserve to be called a nectary; but I could not perceive any nectar, which, as I believe, remains enclosed in the intercellular spaces. The flowers are very small and inconspicuous, but emit a strong