1. Changes through secondary growth. In discussing the differences found in the several species of Ranunculaceæ examined, I have made three types of structure on the basis of the changes taking place through secondary growth. First, those plants which show no marked change of root structure, the primitive radial type of structure persisting in the older roots. In this class I include Ranunculus acris, R. Pennsylvanicus, R. recurvatus, R. septentrionalis, R. hispidus, R. fascicularis, R. bulbosus, R. multifidus, R. circinatus, R. aquatilis var. trichophyllus, Hepatica acutiloba, H. triloba, Aconitum Noveboracense, Trollius laxus, and Caltha palustris. Second, those plants showing a greatly marked change in the bundle area through growth of secondary xylem rays, which by their great development conceal the primitive radial type as found in the younger roots. To this class belong Clematis Virginiana, C. verticillaris, Cimicifuga racemosa, Actæa alba, A. spicata var. rubra, Anemone Virginiana and its var. alba, A. Pennsylvanica, Coptis trifolia, Hydrastis Canadensis and Ranunculus sceleratus.Third, those plants which show in the older roots a great development of the central cylinder and a corresponding decrease of the cortex region. This change is partly brought about by the increase of conjunctive parenchyma in the central cylinder, the xylem being all collected at the center and the phloem in several scattered rays radiating from this center. But the decrease in the cortex region of the oldest roots is mainly due to exfoliation, the epidermis and in some cases all but two rows of the cortex cells being thrown off, so that the endodermis, consisting of many very small regular cells whose walls are generally cutinized, now serves the purpose of an epidermis. This exfoliation was especially noted in the Thalictrums studied. In this type are placed but four of the plants that came under my study, viz.: Thalictrum dioicum, T. polygamum, Anemonella thalictroides and Aquilegia Canadensis.2. Meristem of vegetative point. I have found that the roots of the Ranunculaceæ do not all fall under one type of apical meristem structure, but that there are two main types and a possible subsidiary type to be recognized in these roots. First, a type having a distinct plerome and periblem and a combined dermocalyptrogen. In this type I have placed Ranunculus sceleratus, R. circinatus, R. aquatilis var. trichophyllus, Clematis verticillaris, and probably R. repens, R. fascicularis and R. bulbosus. Subsidiary type, like the first type except that the epidermis is a distinct layer entirely about the vegetative point, though giving birth to the root-cap and so having the same initial groups as the first type. Here are included but two species, Ranunculus acris, and R. Pennsylvanicus. Second, a type in which all the tissues coalesce at the vegetative point, having but one, and this a common, initial group. This type includes the greater number of species studied and is the type in which Erickson and Flahault include the Ranunculaceæ studied by them. The species placed in this type are Aconitum Noveboracense, Anemone Virginiana, and its var. alba, Actæa alba, A. spicata var. rubra, Hepatica acutiloba, H. triloba, Cimicifuga racemosa, Hydrastis Canadensis, Trollius laxis, Thalictrum dioicum and perhaps Ranunculus septentrianalis.