Changes in the nucleus of the ovule.—The preceding remarks have had reference especially to the ovular coats, but it is desirable also to allude to certain points connected with the nucleus. Very frequently, when the coat of the ovule is phylloid, as before described, the nucleus is altogether wanting, though sometimes it is present as a small cellular papilla; very rarely is it to be found in its perfect state. Occasionally the nucleus is present in the guise of a small elongated branch. Wigand cites ovular buds in every stage of progress into a branch, sometimes even bearing indications of anthers. Wydler has observed a similar occurrence in ovules of Alliaria officinalis, and Schimper has described and figured specimens of Nigella damascena in which the outer coats of the ovule were but little changed, while the nucleus was replaced by a leafy shoot. On one of the leaves of this latter was found an imperfect ovule—an ovule on an ovule!

Fig. 148 shows a floret of a species of Gaillardia, in which the ovule was replaced by a leafy shoot which had made its way through a chink in the ovary. In this specimen, however, there was no evidence to show whether the shoot in question was a perverted development of the nucleus, or whether it was wholly independent of the ovule.

Fig. 148.—Floret of Gaillardia, showing leafy shoot occupying the place of the ovule.

From this occasional elongation of the nucleus, as well as from the foliar nature of the ovular coats, Prof. Alex. Braun arrives at the conclusion that the ovule is to be looked on as a bud, the ovular coatings, so often variable in number, representing the scales of the bud, the nucleus corresponding to the end of the axis or growing point. Griffith had previously expressed the same opinion from his observations on malformed ovules of Sinapis and Lonicera, while Caspary's conclusions from the foliaceous ovules of Trifolum repens are somewhat similar. The latter observer considers that the funiculus, with the integuments, is the equivalent of a leaflet, the petiolule or midrib of which answers to the funiculus, and its hollow expansion to the integument. The nucleus itself is considered to be a new formation analogous to a shoot.

M. van Tieghem's conclusion[278] from the examination, of flowers of Tropæolum majus, in which the ovules were replaced by perfect peltate leaves, is that the ovules are foliar productions springing, not directly from a prolonged floral axis, as in Primulaceæ, but from branches of the axis arising from the axils of the carpellary leaves.

Phyllody of the ovules has been met with most often in the following species: