Page:Transactions of the Linnean Society of London, Volume 6 (1802).djvu/98

72 have, seen a single bubble of air escape from the grains of pollen in the whole course of my observations. As their texture was in many cafes quite destroyed, if it had been porous, as that of dry wood, &c. air must have appeared. I therefore conclude them perfectly solid in the dry state.

I think it possible that the prosecution of these inquiries by means of the microscope, may throw some light on the obscure subject of vegetable reproduction; may teach us why the anther is almost always exposed to the air for some time previous to the discharge of the pollen, and this even in aquatic plants; as also what is the office of that saccharine liquor with which the stigma is furnished, and of which such a store is sometimes provided in the nectary. The very manner in which the impregnation takes place may possibly be learned by attentive observation.

The similarity of the unfolded pollen of No. 4. to the form of the plant it comes from, might furnish matter for speculation; but I decline this, believing that experiment and careful observation must always precede found theory.

Reflecting on some of the properties of pollen in which it bears a resemblance to starch, I was led to examine that also in a similar manner, and was not disappointed to find its structure the same. Starch consists of homogeneous grains or capsules shaped like No. 3. capable of imbibing water with increase of bulk and transparency, and of returning to their original state on parting with it. They are also dispersed, with more or less of motion, in spirit; but in this particular different specimens were found to vary, which may be attributed to difference in age or soundness. If a little wheat flour be mixed with water and spread on the glass, these grains appear in great abundance, mixed with fibrous matter. Other kinds of grain afforded the same result, with a difference in the form of the