8. Here, again, a very singular condition presented itself: the calyx and corolla separated from each other, the stamens partly developed, the axis continued beyond the corolla, branched and bearing normal leaves so as exactly to resemble an ordinary stem, while in consequence of the calyx and corolla being bent down to the ground, adventitious roots were developed from the axis on the under side above each of them. In another case, where the calyx and corolla were approximated, the ovary was open above, and sent out six shoots from within, perfectly developed, clearly representing the central placenta and five axile buds, and each giving out a number of adventitious roots at its base."
In other genera of the same order (Primulaceæ) an extension of the placenta into a leafy branch has been observed, as in Lysimachia, where in one case the prolonged placenta was removed and struck as a cutting.[120]
In Ericaceæ too, the axile placenta has been seen ovuliferous at the base and prolonged above into a leafy branch.[121]
Median floral prolification.—This is of more frequent occurrence than the preceding. The prolonged axis is more frequently terminated by a flower-bud than by a leaf-bud, though it must be remarked, that the lengthened and protruded stem frequently bears leaves upon its sides, even if it terminate in a flower, and thus the new growth partakes of a mixed leafy and floral nature. Instances of this kind have long been familiar to observers, and have always excited attention from the singularity of their appearance. In one of the old stained-glass windows, apparently of Dutch manufacture, in the Bodleian Picture Gallery at Oxford, is a representation of a Ranunculus affected with median floral prolification.[122] In pinks the affection is not unfrequently met with. Fig. 60 shows an instance of the kind copied from Schotterbec.
A singular instance of prolification in the central flower of one of the verticillasters of Phlomis fruticosa fell under my own notice; it was a case wherein the calyx was torn on one side, and one of its lobes had become petaloid. Between the calyx and the corolla were three or four spathulate, hairy, bract-like organs; the corolla and stamens were unchanged; but in place of the usual four-lobed ovary there was a single carpel with a basilar style, terminated by a forked stigma. Occupying the place of the other lobes of the pistil was an oblong woolly flower-bud, consisting of calyx, corolla, and stamens, but with no trace of pistil. I have been unable to find recorded any instance of malformation among Labiates or Borages at all similar to this. It differed from most other examples of prolification in that the axis was not prolonged, the adventitious bud occupying precisely the position of the three lobes of the ovary that were absent. The sole remaining carpel had a style and a stigma as perfect in appearance as though the pistil had been complete.
Fig. 60.—Flower of Dianthus affected with median floral prolification.
In a flower of Conostephium (Epacridaceæ) 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: Ranunculaceæ, Caryophyllaceæ, Rosaceæ; while it is commonly met with in Scrophulariaceæ, Primulaceæ and Umbelliferæ. 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.