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 540 ON THE ORGANS AND MODE OF FECUNDATION

its descent being gradual until the cords nearly equal the length of the placenta, to which they are parallel and approximated.

That these cords are not in any degree derived from those portions of the walls of the cavity of the ovarium, to which they are closely applied, and which I have termed the conducting surfaces, is manifest from the identity in state of those surfaces before and after the production of the cords.

In Bonatea the first evidence of the action of the pollen consists in the withering of the stigma ; a similar decay of the greater part of the style soon follows, and the enlarge- ment of the ovarium generally begins before the Avithering of the style is completed. When the enlargement of the ovarium is considerable, and the mucous cords are fully^ formed in its cavity, a corresponding enlargement of the ovula takes place, and the nucleus becomes first visible.

I have no satisfactory observations in Bonatea respecting any tubes going off from these cords and mixing with the ovula ; but in Orchis Morio I have repeatedly and very clearly observed them scattered in every part of the surface of the placenta, and in not a few cases have been able to 7i3] trace them into the aperture of the ovulum, to which they adhere with considerable firmness."

At what period they reach the foramen of the testa, whether before or immediately after the first faint appear- ance of the nucleus, I have not yet been able to determine. That the tubes thus traced to the foramen of the ovulum are of the same nature as those which I have called mucous tubes, and not those directly produced l3y the polleU; is proved by their exact agreement with the former in every respect, except in their being remarkably and irregularly fiexuose, apparently from the numerous obstacles they have to overcome after leaving the cords and beginning to mix with the ovula ; for in the cords themselves, where the

^ [" Carefully" in the original — an obvious error of the press. — Edit.] - Since these additional observations were read, I have found in several other Orchidcse, especially //(^^/^t'/v^/!//^ viiidis and Ophrys apifera, tubes scattered over the surface of the ])laceuta, and not unfrequently inserted, in like manner, into the apertures of ovula.

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