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 520 ON THE ORGANS AND MODE OF FECUNDATION

which, though probably originating with Richard in 1799/ and briefly stated by him in 1802/ was first distinctly ex- pressed as a conjecture in 1789 by M. de Jiissiea.

In 1817, Mr. Stephen Elliott states that he observed, in his Fodostifjmcc' — a genus nearly alUed to Asclepias — a fibre or cord extending through the centre of the corpuscu- lar pedicel or attenuated base of the stigma, and commu- nicating from the anthera to the ovarium. He adds, that Dr. Macbride has since seen it in some species of As- clepias.

There can be no doubt that the cord here noticed is of the same nature with that which Gleicheu has described in a different state, and of which I shall presently have occa- sion to speak.

720] In 1824, Professor Link/ while he admits the distinct origins of the pollen masses and glands or corpuscula seated on the angles of the stigma, yet considers botli these parts as equally belonging to the anthera. In this respect his opinion is identical with that of Gleicheu. The pollen mass, he adds, is composed either of a cellular tissue, or manifestly of grains of pollen : the former part of the description being no doubt meant to apply to true Ascle- piadeae, the latter to Periplocege.

Professor L. C. Treviranus, in 1827," published some observations on this family, in which his account of the structure of the pollen differs in several points from that exhibited in Mr. Bauer's drawings, which he states he had seen three years before this publication.

In Asclepias curassavica, the species more particularly examined by Treviranus, he describes the pollen mass as filled with compressed, nearly round but obtusely angular, colourless, simple grains, containing minute granules; the pressure of the external grains, or those in contact with the general covering, giving it the appearance of being cellular.

In speaking of the mode of impregnation, he says, that the pollen mass, at the time when its connection is esta-

' i:)ici/cl. Botan. i, p. 212. 2 BiilUard, Bid. de Bot. ed. 2, p. 56.

2 Bot. of Carol, and Georg. i, p. 327. " Phil. Bot. p. 300. ^ Zcitsch.f. Physiol. \\, p. 230.

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