Fig. 30.—Dialysis of the sepals and petals in Correa.
Dialysis of the corolla is likewise of frequent occurrence, either partially or to such an extent as to render the corolla truly polypetalous. Among Labiatæ the upper lip of the corolla may be often met with partially cleft, as it is constantly in Phlomis biloba, or more markedly among the Lobeliaceæ.
In the Compositæ, a similar separation of the petals is not infrequent, thus showing frequent transitional stages between the labiatifloral and tubulifloral divisions respectively. The ligulate corollas also may often be found in Chrysanthemums, Dahlias, &c., more or less deeply divided into their component parts.
A more complete separation occurs not unfrequently in Campanula, Rhododendron, Phlox, &c. Figs. 30 and 31 illustrate dialysis of the corolla; the first in Correa, the second in Campanula.
Fig. 31.—Dialysis of the corolla in Campanula sp., after De Candolle.
In the last-named genus, C. rotundifolia has been found with polypetalous flowers in a wild state in the mountains of Canton Neufchatel, Switzerland, and gave rise to the creation of a new genus. This form is now introduced into gardens.