the tracheae of the style to the ovula, which it enters, if I rightly
understand him, by the funiculus umbilicalis: at the same time he seems
to admit the existence of the aperture in the coat.

(*Footnote. Discours sur la Structure des Fleurs page 20.)

In 1745, Needham,* and in 1770, Gleichen,** adopt the hypothesis of
Morland, somewhat modified, however, as they consider the particles in
the grains of Pollen, not the grains themselves, to be the embryos, and
that they enter the ovula by the umbilical cord.

(*Footnote. New Microscopical Discoveries page 60.)

(**Footnote. Observ. Microscop. page 45 et 61 paragraph 118.)

Adanson, in 1763,* states the Embryo to exist before fecundation, and
that it receives its first excitement from a vapour or aura proceeding
from the Pollen, conveyed to it through the tracheae of the style, and
entering the Ovulum by the umbilical cord.

(*Footnote. Fam. des Plant. tom. 1 page 121.)

Spallanzani,* who appears to have carefully examined the unimpregnated
Ovula of a considerable variety of plants, found it in general to be a
homogeneous, spongy, or gelatinous body; but in two Cucurbitaceae to
consist of a nucleus surrounded by three coats. Of these coats he rightly
supposes the outermost to be merely the epidermis of the middle membrane
or testa. Of the relative direction of the testa and inner coat in the
two plants in question he takes no notice, nor does he in any case
mention an aperture in the Ovulum.

(*Footnote. Fisica Anim. e Veget. tome 3 page 309 to 332.)

Gaertner, who, in the preface to his celebrated work, displays great
erudition in every branch of his subject, can hardly, however, be
considered an original observer in this part. He describes the
unimpregnated Ovulum as a pulpy homogeneous globule, whose epidermis,
then scarcely distinguishable, separates in a more advanced stage, and
becomes the testa of the seed, the inner membrane of which is entirely
the product of fecundation.* He asserts also that the Embryo constantly
appears at that point of the ovulum where the ultimate branches of the
umbilical vessels perforate the inner membrane; and therefore mistakes
the apex for the base of the nucleus.

(*Footnote. Gaert. de Fruct. et Sem. 1 page 57, 59 et 61.)

In 1806 Mons. Turpin* published a memoir on the organ, by which the
fecundating fluid is introduced into the vegetable ovulum. The substance
of this memoir is, that in all Phaenogamous plants fecundat