A REVISION OF CERTAIN SPECIES OF PLANTS OF THE GENUS ANTENNARIA. By Elias Nelson. Scieniific Ai<L U. S. Department of A(jrietiJliire. Recent study of the genus Anton niiria in North America has been contined almost entirely to the o-roup represented by .1. (djVHa, A. dioka, and A. plantaglnifolia of Gray's Synoptical Flora. These, as treated by Dr. Gray, have proved to be ac^gregates. The names .1. (djnna and .i. dloJca were originally applied to Old World plants, and it appears that no American specimens are referal)le to those species. Prior to 1897 only live species of the North American continent had been described in this group, viz, ^L planfaghiifolia (Linna?us) Rich-ardson, A. monocephala De CandoUe, A. soUtaria Rydberg (.1. pJanta-ginifolia monocephala Torrey and Gray), A. parolfdia Nuttall, and A. lahradorica Nuttall. During the last four years, however, about 50 additional species have been published. The Antennarias of many parts of North America are as yet little known, and much research in connection with the genus is still necessary. Mr, Fernald has succeeded in arriving at a very satisfactory arrangement of the New England Antennarias. Those of other regions are in need of similar study. In this paper an attempt is made at a natural arrangement of the western and northern species of this group. A tolerably satisfactory synopsis can hardly be expected until more material from this vast region is at hand. Many of the species are very imperfectly known; a considerable number from their type localities only. Especially is this true of the far northern species. Because of the great variability of the species and their very frequent and perplexing intermediate forms, a reasonably complete series of specimens representing each must be obtained before its claim to specific rank can be considered fully established. When more material is secured, it may be found that too many species have been recognized in this paper. In the study of this genus it is of the greatest importance that the identity of each published species be definitely determined, 1 have been very fortunate in having had the opportunity of examining types or typical material of all the species included in this paper except ^1. parvifolla, A. monocepJiala, and A. aisoidrs. The last named is the only species of which I have seen no specimens. Although 1 have Proceedings U. S. National Museum, Vol. XXItl— No. 1230.