A complete list of the rusts of Boone County has not been published. In the year 1889 Dr. B.T. Ga1loway of the U. S. Department of Agriculture, published a preliminary list of the parasitic fungi of Missouri. The specimens which Dr. Galloway collected were destroyed at the time of the fire which demolished the main building of the University in February, 1892. This list included one hundred and two rusts, only three of which are mentioned specifically as having been collected in Boone County. Twenty-six of the list are mentioned as common forms, and were probably found in this immediate vicinity. The larger number of the remainder of the forms were collected in Perry County, located on the Mississippi river in the southeastern part of the state. Since that date a considerable number of specimens has been collected, largely from this region, and placed in the herbarium of the University. The collection contains a total of four hundred and forty-three specimens. Most of these were collected on general field trips taken by different members of the Department of Botany, in the years 1910, 1911, and 1912, but no systematic collection of Rusts has been undertaken. It has been the purpose of the present work to identify the rusts occurring in the collection and arrange them in order according to the classification accepted at the present time. This collection and arrangement may then serve as a basis for further work. The present list doubtless includes but a small portion of the rusts to be found in this region, and the addition to the collection of other forms from this locality, as well as from the remainder of the state, is very desirable. It is quite probably that the rust flora of Missouri is as abundant and diversified as that of any other state.