Many bryophyte species are associated with concentrations of minerals, but in Alaska only two species seem to have an obligate relation to certain minerals; these species are Gymnocolea acutiloba, which grows on or near copper deposits, and Grimmia maritime, which grows on coastal rocks that are continually being coated with sodium chloride from sea spray. Nardia scalaris grows on soil containing 0.6 percent copper, and Oligotrichum parallelum and 0, Uercyni&wm grow on mineralized rock containing 0,26 percent nickel and 0.21 percent copper. Rhacomitrium sudeticum was found growing on copper ore that contains 30.45 percent copper. Soil containing 165-215 ppm (parts per million) copper in the A horizon supports many species. Only Cephalozia Mcuspidata was found growing on an ore vein that contains 12.9 percent lead and 34.0 percent zinc, although several other bryophyte species grew on rock adjacent to the vein. Soil containing 1,300 ppm lead and 870 ppm zinc does not inhibit bryophyte growth. Luxuriant bryophyte mats overlie soil that contains 40 ppm mercury, 95 ppm antimony, and 900 ppm arsenic in the A horizon. Blepnarostoma trichophyllum, Cephalo-zia, bicuspidata, Dicrcmella cerviculata, D. subulata, and LopJiozia wenzelii grow on gypsum evaporite and are incrusted with this mineral. Eleven species grow on tufa deposits, and some species are heavily incrusted. Only a few species grow on pyrite, but many species grow over pyrite bodies on the acid A horizon of soil that contains 200 ppm lead, 150 ppm zinc, and 400 ppm copper. Limonite precipitated from stream water is forming fossil casts of vascular plants and liverworts and, in places, has formed consolidated deposits of these. High iron content in water apparently does not inhibit the growth of bryophytes, and many species occur in this environment. Serpentinized rock weathers to form soil containing as much as 4,000 ppm nickel and 900 ppm chromium, yet these elements have no visible effect on the bryoflora; 21 species, both calcicole and silicole, were found growing on serpentinized rock. Six bryophyte species grow on substrates that are submerged in sea water at high tide, and 23 species were found at sites subjected to sea spray.