[Illustration: FIG. 60.--Flower of _Dianthus_ affected with median floral prolification.] In a flower of _Conostephium_ (_Epacridaceae_) forwarded to me by Mr. Bentham, there was a similar adventitious bud placed by the side of the pistil, but as the latter contained the usual number of cells it is probable that the supernumerary bud in this case originated rather from the side than the end of the axis. Certain families of plants present this deviation from their ordinary structure with greater frequency than others: the following orders seem to be the most frequently affected by it: _Ranunculaceae_, _Caryophyllaceae_, _Rosaceae_; while it is commonly met with in _Scrophulariaceae_, _Primulaceae_ and _Umbelliferae_. Of genera which seem peculiarly liable to it may be mentioned the following: _Anemone_, _Ranunculus_, _Cheiranthus_, _Dianthus_, _Dictamnus_, _Daucus_, _Rosa_, _Geum_, _Pyrus_, _Trifolium_, _Antirrhinum_, _Digitalis_, _Primula_. A reference to the subjoined list of genera affected by this malformation, and the knowledge of its comparatively greater frequency in some than in others of them, will show that it is more often met with in plants having an indefinite form of inflorescence than in those having a definite one. The change may affect some only, or the whole of the flowers constituting an inflorescence; and though it is by no means a constant occurrence, it very frequently happens that the central or terminal flower in a definite inflorescence is alone affected, the others remaining in their ordinary condition, as in pinks (_Dianthus_); and in the indefinite forms of inflorescence, it is equally common that the uppermost flower or flowers are the most liable to be thus affected. In those plants which present this deviation from the ordinary condition with the greatest frequency, it often happens that the axis is normally more or less prolonged, either between the various whorls of the flower, as in the case of the gynophore, &c., or into the cavity of the carpels, as in the instances of free central placentation. To bear out this assertion, the following instances taken from those genera having definite inflorescence, and which are very commonly affected with prolification, may be cited; thus, in _Anemone_ and _Ranunculus_ the thalamus is prolonged to bear the numerous carpels; in _Dianthus_ there is a marked internode separating the carpels from the other parts of the flower; in _Primulaceae_ central prolification is very common, and this is one of the orders where the placenta seems from the researches of Duchartre and others, to be truly a production of the axis within the carpels;[123] in _Thesium_ also, another genus with free central placenta, this malformation has been found.