Part 101. General features. In several respects the crowfoot family is the best one with which to begin our study of plant groups. It forms an especially serviceable standard of comparison because its members, as we shall see, are remarkably simple in their plan of structure-at least for seed-plants- and at the same time the various species display a wide range of variety in detail. Moreover, it was his careful study of this family which led the younger Jussieu to an understanding of those fundamental principles of classification which he applied so brilliantly in founding the natural system. To us it will present problems which once solved will simplify and illuminate all our future study.

Of the plants already examined the following, as we have seen, are of this family: marsh-marigold (Caltha palustris), tall buttercup (Ranunculus acris), ditch crowfoot (R. sceleratus), wind-flower (Anemone nemerosa), and monkshood (Aconitum Napellus). The family is made up of about 700 species in about 30 genera. From the few examples above given and a study of those shown in Figs. 282-297, we may gain, however, a fair idea of the range of peculiarities exhibited by the family as a whole. At first sight it may seem scarcely possible to find among plants which differ so much one from another any peculiarity or set of peculiarities common to all and yet not possessed by other seed-plants. Examination will show us, however, that as a group they may be distinguished at least by the lack of complicating features which other families show, and we shall find furthermore a few positive peculiarities which are more or less characteristic.