Frest, T.J. 1983. Northern driftless area survey. Final report to the Minnesota Department of Natural Resources. 17 pp.
Partial survey in 1981 and 1982 of the Driftless Area and the immediately surrounding Niagaran Escarpment (Paleozoic Plateau of Prior, 1976) has turned up approximately 100 algific talus slopes (term defined in Frest 1981, 1982, 1983). These provide essential habitat for all known colonies of the federally listed (Endangered) Iowa Pleistocene Snail (Discus macclintocki) and several other snail species, as well as for all but Iowa sites for the Threatened Northern Monkshood (Aconitum noveboracense). A single algific site had been previously reported in Minnesota (Hartley 1962), and it was believed probable, based on geologic criteria and a cursory survey of the botanical literature, that many such sites might exist in the Minnesota and Wisconsin portions of the Driftless Area. In the summer of 1982, roughly four weeks of field work (23 days in Minnesota, 9 days in Wisconsin) were conducted with the intent of gauging the approximate extent and distribution of algific sites in these two states.