This falling back from the stage of an organ of fertilization to that of a petal shows that the plant is capable of regressive metamorphosis, and we may conclude from this that in the normal sequence the different organs are transformed from one another by way of progressive metamorphosis. It is evident that the regressive type occurs only as an abnormality, or as a result of artificial cultivation. Plants once brought into this condition frequently show a general state of unrest, so that other organs also are inclined to fall back to a lower level. Thus we may come across a rose, an outer petal of which appears in the form of a leaf of the calyx (sepal), or one of the sepals is found to have grown into an ordinary rose leaf.