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 574 ON THE PLURALITY AND DEVELOPMENT

regard to Cycas, might be considered the revival of the general hypothesis advanced by Morland in 1703/ and some years afterwards adopted, but without acknov^^ledgment, by C. J. GeofFroy,^ and which seems to have entirely origi- nated in the discovery by Grew of the existence of a for- amen opposite to the radicle of the embryo in the ripe seeds of some Leguminous plants.^

But as M. du Petit Thouars had evidently no intention of extending his hypothesis beyond Cycas and probably Zamia^ it can hardly be said to anticipate the general and ingeniously supported theory of Dr. Schleiden, respecting which physiological botanists are at present ahnost equally divided. On this theory it is not my intention at present to express an opinion ; nor did the question of the mode of action of the pollen form any part of my object in the pre- ceding essay. I shall only here remark, that according to the latest statements of Dr. Schleiden with which I am acquainted,^ although he admits that his investigation is not in all points complete, he seems to have no doubt that his theory of the origin of the vegetable embryo in the pollen tube is applicable to Coniferce. He has in the first place ascertained the existence of my areolae or corpuscula, which he denominates large cells in the embryo-sac or albumen, in all the European genera of Coniferce -^ and in Abies excelsa, Taxus baccata^ and Jiiniperus Sabina, he states that he has succeeded in preparing free the whole pollen tubes from the nucleary papillae to the bottom of the corpuscula. But as (if my observations are correct, and they seem to be confirmed by those of M. de Mirbel) the corpuscula are not developed in Pinus, as the genus is at present limited, until the spring or even beginning of summer of the year after flowering, and if Dr. Schleiden's statement be also correct, the pollen must remain inactive for at least twelve months.

The quiescent state of pollen for so long a time is indeed

1 Philosophical Trausactioiis, vol. xxiii, part 2, u. 287, p. 1474.

Mem. de I'Acad. des Sc. de Paris, 1711, p. 210. 3 Aiiat. of Plauts, p. 2. ^ Schleiden, Gruiid. der Bot. 2 Theil, p. 374. ^ Op. cit. pp. 354 et 357,

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