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 522 ON THE ORGANS AND MODE OF FECUNDATION

therefore, was to ascertain the structure of the pollen mass.

^ Although on this subject my earliest observations es- sentially agreed \vith Mr. Bauer's figures of the mass, which represent it as having a subdivided cavity with a grain of pollen in each cell; yet a further examination had led me to adopt the opinion of Treviranus and Ehrenberg, who de- scribe its cavity as being undivided and filled with distinct grains.

722] I was confirmed in this opinion on considering the state of the mass after the production of the pollen tubes; for it appeared very improbable that the cells, unless they were of extreme tenuity, could be either suddenly removed or sufficiently ruptured to admit of the passage of the tubes from its more distant parts to the point or line of dehis- cence.

The appearance, however, occasionally met with, of lacerated membranes proceeding, as it seemed, from the

^ [111 the orig-inal impression, printed for distribution in October, 1831, the passage from this point down to the paragraph on p. 524 commencing " On the 16th of July," stood as follows. This was replaced in the 'Linnean Trans- actions' b}^ that which is given in the text. — Edit.]

"My earliest observations on this subject, made on several species of Asclejnas, seemed to prove that the mass is cellular, nearly as Mr. Bauer has represented it. But on a further examination I was convinced that it can be termed cellular only in the early stages, in consequence of the state of the grains of pollen which then certainly cohere; while in the more advanced, and especially in the mature state, it is no longer really cellular, the grains being now distinct from each other; sections of the mass, however, whether trans- verse or longitudinal, still exhibit a cellular appearance.

"These grains, when in this their perfectly developed state, are colourless, nearly round, but slif^htly and obtusely angular, probably from mutual pressure, much compressed, with an undivided cavity, and no indication of their being composed of four or any other number of united cells. Their membrane is transparent, and has no appearance of being made up of two united coats, and the cavity is filled and rendered opaque by spherical granules of nearly uniform size, with occasionally a few oily particles. In this state no appearance or indication of the tubes or appendages described by Dr. Ehrenberg was found.

"The general covering of the mass, which is of a deep yellow colour and very distinctly areolated, the meshes being angular, and in size as well as in form nearly corresponding with the included grains, may perhaps be considered as the outermost series of cells, whose laminse are closely applied to each other, as in the epidermis, and their cavity consequently obliterated. They thus form a coat of considerable thickness, necessary for the protection of the grains of pollen, in a mass which is destined to be removed from its original place by an insect, and applied by this agent to a distant part of the same or of a different flower."

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