The accompanying paper by AS Hitchcock, Systematic Agrosologist of the United States Department of Agriculture, and Agnes Chase, Assistant Agrostologist, is supplemental to a revision of the genus Panicum published by the same authors in volume 15 of the Contributions under the title of" The North American Species of Panicum." As stated in the preface to that paper, it was impossible at that time to offer a satisfactory treatment of the tropical species. Since then much additional material, including collections made by he authors, has been accumulated. The present paper includes the results of the study of these collections and presents a fairly detailed

There are included 116 species and 3 subspecies. Of these, 9 species are described as new; 5 are South American species which were unknown within the limits of the area covered; 1 is a species recently described; and 4 are species that were included in the list of synonyms or of dubious species but are now considered valid. In all 19 species are added, making the total for the genus Panicum in North America 216. Each species is accompanied by an outline map graphically epresenting the geographical distribution within the Tropics of North