In the accompanying figures (fig. 165, a-h) a series of intermediate stages is shown between the ordinary stamen of Sempervivum tectorum and the ordinary carpel, from which it will be seen that the filament is little, if at all, affected, and that in those cases where there is a combination of the attributes of the stamen and of the pistil in the same organ the pollen is formed in the upper or inner surface of the leaf-organ, while the ovules arise from the opposite surface from the free edge, (b, c, d, e, f, g).

In a drawing made by the Rev. G. E. Smith of a malformed flower of Primula acaulis, and which the writer has had the opportunity of examining, the stamens are represented as detached from the corolla, and their anthers replaced by open carpels, with ovules arising, not only from their edges, but also from their surfaces, while the apex of the carpellary leaf was drawn out into a long style, terminated by a flattened spathulate stigma.

Delphinium elatum is one of the plants in which this change has been most frequently noticed.[347]

Fig. 165.—Sempervivum tecotorum. a. Normal stamen. h. Normal carpel. b, c, e, f, g. Structure partly staminal, partly carpellary. d. Transverse section through c, showing pollen internally, ovules externally.

In willows the change of pistils into staminal organs has been frequently observed. In Salix babylonica Prof. Schnizlein has described various transition stages between the carpels and the stamens, and in one instance, in addition to this change, a perfect cup-shaped perianth was present, as happens normally in Populus[348]. Mr. Lowe also records the conversion of stamens into ovaries in Salix Andersoniana, and this by every conceivable intermediate gradation.[349]

The following list will serve to show what plants are most subject to this anomaly. It is difficult to draw any accurate inference from this enumeration, but attention may be called to the frequency of this occurrence in certain plants, such as the Sempervivum, the wallflower, the poppy, and the heath. Why these plants should specially be subject to these changes cannot be at present stated.

By the student of animal physiology such a change as above described—equivalent to the substitution of an ovary or a uterus for a testis—would be looked on as next to impossible; the simpler and less specialised structure of plants renders such a change in them far more easy of comprehension.