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 501 ON THE ORGANS AND MODE OF FECUNDATION

have effectually concealed their true nature ; and accord- ingly they have uniformly been considered as forming parts or appendages of the labellum, with which indeed their bases cohere. That they are really stigmata, how- ever, I have proved by a careful examination of the tissue of their secreting surface, by the action of the pollen arti- ficially applied to this tissue, by the descent of its tu]:)es, hereafter to be described, along the upper surface of the styles which is destitute of epidermis, and by the conse- quent enlargement of the ovarium. Di/domeris of Mr. Don,^ which may also be regarded as a species of Habe- naria, is another example of nearly the same kind ; and the 702] description of stigma which, in 1813, I introduced into the character of Sat^riuiu,^ implies an analogous develop- ment in that genus.

On the relative position of stamina and stigmata in the column of an Orchideous plant, it may be remarked that there is hardly an instance of a perfectly developed stamen and stigma placed opposite to each other, and consequently deriving their vessels from the same cord.

Tor, in the ordinary structure of the family in which only one perfect stamen is produced, the corresponding stigma loses entirely or in great part its proper function, which it recovers, so to speak, in those cases where this stamen becomes imperfect, or is destitute of an anthera : and hence, perhaps, it may be said that to obtain in any case the complete devolopment of the lateral stamina, and, what is of greater importance, to ensure in all cases the perfection of the lateral stigmata, these organs are never placed opposite, but uniformly alternate with each other.

The general conformation of the ovarium, v/ith regard to the number and relative position of the parietal placentae, and the arrangement of their numerous ovula, has long been well understood. But the early structure and evo- lution of the unimpregnated ovulum have not yet, as far as I know, been in any degree attended to.

In its gradual development, the ovulum exhibits a series

' Frodr. Flor. Nepal, p. 26.

- Ait. Hort. Keto. ed. 2, vol. v, p. 196.

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