Echinochloa crusgalli and E. muricata are different species, E. crusgalli being Eurasian in origin, E. muricata North American, but they were not distinguished in the 1951 edition of the Manual of Grasses of the United States. Because of the high regard in which Hitchcock and Chase were held, many regional treatments also combined the two species. The illustration of E. crusgalli provided in the Manual aggravated the problem for it is of E. muricata, not E. crusgalli. Developing a taxonomic treatment in which both species are recognized is relatively easy. Harder, in fact impossible, is sorting out the consequences of lumping the two species on such things as distributional data. This became evident from attempting to use published data to prepare distributional maps for the two taxa. Echinochloa crusgalli was shown as an ubiquitous species, which came as no particular surprise; E. muricata had huge holes in its distribution, holes that frequently corresponded to a state. I have examined over 600 specimens from eastern herbaria to attempt to correct the maps of E. muricata; what this exercise does not do is tell whether any of the records for E. crusgalli should be eliminated. One way around this problem is for herbaria to collaborate in making regularly updated, specimen-based data available on a central map server. This would also require willingness to accept, for this purpose only, a common taxonomic treatment. The Flora North America project offers, for the first time, a reasonable prospect for having such a treatment for North America north of Mexico. We need to find ways to exploit the value of the project as each volume becomes available.

Key words: distribution maps, Echinochloa, Flora North America