Several authors, notably Fernald (1925), Stebbins (1935), Guire and Voss (1963), and Voss (1972), have noted that the vegetation of the shores of the Great Lakes, and especially that of the dunes, pannes, and beach pools along the northern shores of Lakes Michigan and Huron, includes a number of species which are virtually restricted to these habitats, rarely if ever occurring elsewhere in the Great Lakes region. (The term "panne" is used here for a relatively low area, consistently moist but not inundated, between dunes or behind a dune paralleling the shore. Such moist depressions are also known as "slacks" or "wet, sand-flats.") A few of these species are endemic to the Great Lakes region; others occur in populations which are disjunct, to various degrees, from populations of the same species in other parts of North America.