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ON THE SEXUAL OKGANS OF THE CYCADACE^. 67
that of Uossmanu. According to this observer (Bot. Zeitung, 1855, p.
666) from the examination of a monstrous Aquilegia, the border of the
carpellavy leaf divides into as many lobes as there are fiinicles. These
are the equivalents of the lobes, and bear the ovules which originate in
the parenchyma of the lobes, but the nucleus is a new and distinct
{NeubiUhing) production, giving rise also to the formation of the coats.
According to this view, the coats would neither be a product nor a pro-
longation of the edges of the carpel. Brongniart had previously based on
a monstrous Delphinimn the following theory :—An ovule is the equiva-
lent of a lobe or tooth of a leaf. The funicle with the raphe, as far as
the chalaza, are formed by the vein of the lobe. The nucleus is an in-
dependent formation which makes its appearance on the upper surface
of the lobe, but the coats are nothing more than the folded extremities
of the lobe ("Lobe foliace replie sur lui-meme en formant une sorle
de capuchon," Archives du Museum d'Histoire Nat., iv. 1844).
For anatropous ovules there is something seductive about this theory,
but it leaves unexplained the existence of double coats, and does not
determine the precise point from which the formation of the nucleus
starts. The observations on which it rests as well as those of Wesmael
(Bulletin de I'Academie de Bruxelles, xviii. p. 12) of the replace-
ment of ovules by leaflets or leafy lobes, are of great value as ar-
guments against the theory of axile placentas, but they do not at pre-
sent appear to be able to supply an adequate explanation of the
formation of the ovules themselves.*
The production of ovides on the edges or upper surface of carpellary
leaves has been well compared to the formation of buds in the same
positions on ordinary leaves,—a phenomenon which is far from being
uncommon, either in cultivated or uncultivated plants, and which, con-
sidering the low differentiation of the tissues in the vegetable organism,
is not very remarkable. The unintermitted production of a succession
of buds and axes, which remain united, or separate as distinct indi-
viduals, is the essential character of all plants. Although as yet it has
eluded direct observation, we can only picture to ourselves the forma-
tion of a bud as originating in a cell differentiated from neighbouring
cells. In this cell therefore the bud, that is the new individual, is
* The observations of Marchand (Adansonia, iv. p. 159), and of Kiraehleger
(Pollicliia, xsviii. p. Ill), on ovules partly transformed into leaves, as well
as those of Cramer, are only known to me from quotations.