A study of the hepatics of the Douglas Lake region was begun at the UMBS, Cheboygan, Michigan during the summer of 1947. During this session and in the summers of 1948 and 1949, a total of 89 species and 50 genera of liverworts were collected and studied. Numerous collections and identifications were made with special emphasis on those hepaticae occurring in Cheboygan, Emmet, Presque Isle, and Mackinac counties. Data and specimens of all available material were accumulated to be utilized in the construction of an illustrated key which may prove useful to other students of hepaticae. Original illustrations have been prepared for the majority of species. Whenever possible, vegetative characters have been given prominence over reproductive characters, since liverworts are most often collected in a sterile condition. The system of classification used in this study is that given by A. W. Evans in "The Classification of the Hepaticae" (Bot. Rev. 5: 49-96. 1939).