Fig. 159.—Petaloid stamens, Hibiscus.

Petalody of the connective is of less frequent occurrence than the corresponding change in the other portions of the stamen. It may be seen in some forms of double columbine,[310] in which the connective forms a tubular petal or nectary, and in double petunias and fuchsias. When it occurs, the true anther-lobes are usually atrophied, and little or no pollen is formed.

An occurrence of this nature in Tacsonia pinnatistipula, in conjunction with the partial detachment of the stamens from the gynophore, led Karsten to establish a genus which he called Poggendorffia.[311]

From the subjoined list of genera in which petalody of the stamens, in some form or other, has been observed, it will be seen that it happens more often in plants with numerous distinct organs (Polypetalæ, Polyandria, Polygynia, &c.) than in other plants with a smaller number of parts, and which are more or less adherent one to the other. The tendency to petalification is, moreover, greater among those plants which have their floral elements arranged in spiral series, than among those where the verticillate arrangement exists; and in any given flower, if the stamens are spirally arranged while the carpels are grouped in whorls, the former will be more liable to petalody than the latter, and vice versâ. It has been before remarked, that this condition is far more common in plants whose petals, &c., have straight veins, like those in the sheath of a leaf, than in those the venation of which is reticulate, as in the blade of the leaf. It must also be remembered that in the same genus, even in the same species, different kinds of doubling occur. Familiar illustrations of this are afforded in the case of anemones, columbines, fuchsias, and other plants.

The existence of "compound stamens" in some flowers, as pointed out by Payer, and others, and the researches of Dr. Alexander Dickson, confer additional importance on the subject of petalody, and necessitate the examination of double flowers with special reference to these compound stamens, and to the order of their development.[312] The presence of these compound stamens affords a satisfactory explanation of the appearance in some double Malvaceæ, wherein the tufts of adventitious petals are very liable to be mistaken for buds, produced by axillary prolification in the axils of the petals, but which are in reality compound and petaloid stamens. At other times, however, true axillary prolification exists in these flowers; but then the supplemental florets have always a calyx, which is wanting in the other instances.

Petalody of the stamens has been met with most frequently in the following genera:

Petalody of the pistils.—Taken by itself, this is much less common than the corresponding change in the stamens. It generally affects the style and stigma only, as happens normally in Petalostylis, Iris, &c., but this is by no means always necessarily the case. In some of the cultivated varieties of Anemone and Ranunculus all the parts of the flower remain in their normal state, except the pistils, which latter assume a petaloid appearance.