It has become increasingly popular in lichenology to stress characteristics based solely on chemical constituents rather than the traditional morphological features typical of plant systematics. The basis for chemical species formation is not clearly understood. The chemical differences are believed to be of genetic origin. However, the effects of habitat and substrate on the chemical nature of the podetia have not been extensively explored. Investigations with Parmelia bolliana (Hale, 1967) and Cetraria ciliaris (Graham, 1969) have indicated that the environment is not related to the cause of chemical species formation. Zopf (1903) did find evidence of such a relationship with the environment in the Pseudevernia complex; however, similar results have not been extensive enough to justify any reliable, overall conclusions. The Cladonia chlorophaea group consists of four chemical species each of which differs essentially by chemical constituents. The acid fumarprotocetraric is the only acid present in the Cladonia chlorophaea (Florke) Spreng. The other chemical species, which may or may not include fumarprotocetraric acid, are C. cryptochlorophaea Asah. containing cryptochlorophaeic acid, C. grayi Merr. containing grayanic acid, and C. merochlorophaeae Asah. containing merochlorophaeic acid. C. chlorophaea ranges throughout the US; C. cryptochlorophaea and C. grayi are widespread in the northeastern and midwestern portions of the country; and C. merochlorophaea occurs in the Great Lakes region and northern New England. These distinct ranges suggest taxonomic significance. The purpose of this investigation was fourfold: First, to establish the percentage of each species within the total population in the vicinity of the UMBS, (Cheboygan County, Michigan). Second, to determine whether these percentages vary within any of the ecological communities tested. Third, to test for substrate specificity. Fourth, to determine whether there are morphological differences in the podetia of the various species.