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 and I accordingly examined numerous species of many of the more important and remarkable families of the two great primary divisions of Phænogamous plants.

In all these plants particles were found, which in the different families or genera, varied in form from oblong to spherical, having manifest motions similar to those already described; except that the change of form in the oval and 6] oblong particles was generally less obvious than in Onagrariæ, and in the spherical particle was in no degree observable. In a great proportion of these plants I also remarked the same reduction of the larger particles, and a corresponding increase in the molecules after the bursting of the antheræ: the molecule, of apparently uniform size and form, being then always present; and in some cases, indeed, no other particles were observed, either in this or in any earlier stage of the secreting organ.

In many plants belonging to several different families, but especially to Gramineæ, the membrane of the grain of pollen is so transparent that the motion of the larger particles within the entire grain was distinctly visible ; and it was manifest also at the more transparent angles, and in some cases even in the body of the grain in Onagrariæ.

In Asclepiadeæ, strictly so called, the mass of pollen filling each cell of the anthera is in no stage separable into distinct grains; but within, its tesselated or cellular membrane is filled with spherical particles, commonly of two sizes. Both these kinds of particles when immersed in water are generally seen in vivid motion; but the apparent motions of the larger particle might in these cases perhaps be caused by the rapid oscillation of the more numerous molecules. The mass of pollen in this tribe of plants never bursts, but merely connects itself by a determinate point, which is not unfrequently semitransparent, to a process of nearly similar consistence, derived from the gland of the corresponding angle of the stigma.