Floristic botany in the Mackinac Straits region has had a long history with the result that this has become one of the better known areas in the upper Midwest. Pioneer botanical explorations are reported to have begun with Thomas Nuttall, who, in 1810, was the first botanist known to collect in the region. Additional 19th century explorations and plant collections were made by Douglass Houghton, N. H. Winchell, E. J. Hill, Charles F. Wheeler, C. W. Fallass, and others. With the establishment in 1909 of UMBS on Douglas Lake, near the boundary between Emmet and Cheboygan counties, the number of observations and collections increased. An annotated list and supplements to it were published by Gates and Ehlers between 1925 and 1948. More recently, Voss (1954) compiled a checklist of the vascular plants for the two-county Douglas Lake region, to which additional information, including a detailed history of floristics in the area, has been added (Voss, 1956, 1957). In addition to these major studies are the observations and collections of numerous Biological Station teachers, researchers, students, and visitors, some of them specialists on particular groups, which have contributed considerably to the thoroughness with which the areas has been covered. For an area rich in botanical activities it seems well to place on record a few new observations. Since these are based solely on my own collections, they are not to be considered a complete list of species new or rare in the region, as other collectors may well have additional records. Both my observations for the Mackinac Straits region and those from elsewhere in the state were made incidental to other field work in connection with graduate studies during the summers of 1958, 1959, and 1960. In the preparation of this report, I have consulted the herbaria at the U. of Michigan, the Biological Station, Cranbrook Institute of Science, Michigan State U., and for Geocaulon, the Gray Herbarium of Harvard U. Voucher specimens are at the U. of Michigan Herbarium unless otherwise noted.