Plates II and III show two series of leaves which are so arranged as to represent definite stages in the growth-process of the plant concerned. In each sequence shown the leaves have been taken from a single plant, in which each leaf-form was repeated, perhaps several times, before it passed over into the next stage. The leaves on Plate II come from a Sidalcea (of the mallow family), those on Plate III from a Delphinium. We will describe the forms in sequence, so that we may grasp as clearly as possible the transition from one to another as presented to the eye.