Inverness Mud Lake, a relic bog formation occurring in the transitional region between the coniferous forest to the north and the deciduous forests on the south, has been the subject of several floral and ecological investigations in the past. These studies of Coe, Erickson, and Woollett (1924) and of Gates (1942) contain only species lists of the vascular plants occurring in the area and mention brief descriptions of the vegetation features. Therefore, the major objectives of this investigation were to evaluate quantitatively the vegetation composition and structural relationships of the various plant communities comprising the Mud Lake area; and to utilize the methods of the Zurich-Montpellier School of Phytosociology for this evaluation. Three ecologically distinct communities occurring along the southeast margin of the lake were studied: the Thuja seepage, the Sphagnum bog extending east from an ice-push ridge near the lake margin, and the quaking Carex mat bordering the open water of the lake.