Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/238

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218
VANDEÆ.
Chap. VII.

disc, as a protection to the pollen-masses from being permanently glued to the viscid disc.

From observations made on fifteen flowers, it was ascertained that the straightening of the pedicel does not occur until from twelve to fifteen minutes have elapsed. The first movement causing the act of ejection is due to elasticity, and the second slow movement to the drying of the outer and convex surface; but this latter movement differs from that observed in the pollinia of so many Vandeæ and Ophreæ, for, when the pollinium of this Mormodes was placed in water, it did not recover the hoop-like form which it had at first acquired by elasticity.

The flowers are hermaphrodites. The pollinia are perfectly developed. The elongated stigmatic surface is extremely viscid and abounds with innumerable utriculi, the contents of which shrink and become coagulated after immersion for less than an hour in spirits of wine. When placed in spirits for a day, the utriculi were so acted on that they disappeared, and this I have not noticed in any other Orchid. The ovules, after exposure to spirits for a day or two, presented the usual semi-opaque, pulpy appearance common to all hermaphrodite and female Orchids. From the unusual length of the stigmatic surface I expected that, if the pollinia were not ejected from the excitement of a touch, the anther-case would have detached itself, and the pollen-masses would have swung downwards and fertilised the stigma of the same flower. Accordingly, I left four flowers untouched; after they had remained expanded from eight to ten days, the elasticity of the pedicel conquered the force of attachment and the pollinia were spontaneously ejected, but they did not fall on the stigma and were consequently wasted.