The important features of vascular anatomy of the flower of certain unusual forms of Ranunculus, Caltha, and Delphinium, together with the important features of floral vascular anatomy of the families Menispermaceae, Calycanthaceae, and Annonaceae have been presented. The facts pertinent to each of these groups have been discussed and summarized at the end of each section; but a general concluding summary of the features common to all four groups is necessary. The floral organization of these groups supports the view already expressed, that in the more primitive flower the carpels are three-trace and multiovulate; the stamens are single-trace structures, and the lowest may be normally and naturally in the form of petals, or all may be transformed into petals by horticultural manipulation; the sepals are three-trace trilacunar structures, but may become modified into single trace unilacunar or multitrace, multilacunar structures; all floral parts are spirally inserted and indefinite as to number. As regards the origin of the Menispermaceae, Calycanthaceae, and Annonaceae, the vascular skeleton of each gives undoubted evidence of origin from the Ranunculaceae. The study of the vascular skeleton of the flower of Menispermum canadense shows that it has been derived directly from some member of the Ranunculaceae which displayed a tendency toward cyclic arrangement of parts, the reduction of parts to a definite numerical plan, a uniovulate carpellary condition, and a single strand vascular supply to the individual appendage. At the same time the Menispermaceae demonstrate that they do not lead to any advanced group. The definite development of the imperfect flower makes this impossible. The floral vascular skeleton of the Calycanthaceae demonstrates that this family is also a diverging side line from the Ranunculaceae. The receptacle has become cup-shaped, due to a checking of the growth of the apical (carpellate portion) floral primordium and a consequent bulging up of the surrounding floral primordium to form the cup. Such a condition illustrates a possible step in the mode of origin of the inferior ovary. However, the Calycanthaceae, as the Menispermaceae, are a closed line because the anatomical evidence at hand points to the inferior ovary of the Rosaceae and other dicotyledons as arising through a cohesion and adhesion of floral parts, rather than after the fashion suggested by Calycanthus. The floral vascular skeleton of the Annonaceae is clearly that of the Ranunculaceae, but possessing one peculiarity, a partially developed cortical vascular system. This characteristic is seldom found in a vegetative axis, and has never been found in another floral axis except possibly the Calycanthaceae; therefore the Annonaceae also represent a closed series. Thus the evidence gained from a study of these three families points to the Ranunculaceae as the crucial center of the order.