Ichnanthus P. Beauv. comprises approximately 39 species of grasses; one is confined to tropical Asia, Africa, and Australia; the remainder are widely distributed in the American tropics. Ichnanthus is closely related to Echinolaena and Oplismenus, and to both section Panicum and the "Stolonifera" group of Panicum. It differs from these related taxa in one character of the fertile floret of the spikelet- two extensions from the rachilla of the upper lemma that are either actual winged structures or wing-like sclerified areas (also called excavations) at the base of the upper lemma by which the two sections are distinguished. In section Ichnanthus, the two winged appendages are attached to the base of the upper lemma; 19 species of this section are described. In section Foveolatus, wing-like sclerified areas are present at the base of the upper lemma. Anatomical observations and 13C/12C ratios for selected species suggest that Ichnanthus includes only C3 grasses with the typical Calvin cycle of photosynthesis. The primary problem facing most taxonomists who deal with Ichnan- thus is identification of species. After surveying recent treatments of the species of Ichnanthus by Swallen (1964a, b) and Rogers (1969, 1971, 1972, 1973), I was convinced that the generic limits had become too vague. My first task then was to determine the generic limits of Ichnanthus. It was also quite apparent that over the years an accretion of species had made Ichnanthus nomenclaturally perplexing. A second objective, then, was to clarify the nomenclature and to establish a workable taxonomy of each species. This was accomplished by using, for the most part, alpha-taxo- nomic techniques.