Nine samples of Sphagnum fuscum (Schimp.) Klinggr., one each of S. magellanicum, S. nemoreum, S. wulfianum, and Dicranum polysetum, and seven samples of Larix laricina have been analyzed for mineral ash content, Al, B, Ca, Fe, K, Mg, Mn, and P. The chief influence upon the ash content of Sphagnum fuscum in ombrotrophic bogs which are dependent for their mineral supply solely upon the atmosphere is clearly windblown soil from cultivated farmlands. Bogs unaffected by human settlement and therefore not subjected to greater mineral supply are now restricted to wilderness areas in the northeastern part of Minnesota. Sphagnum serves as an effective trap for dust fall and is much richer in the lithophile elements Al and Fe than the needles of the tamarack, Larix laricina, from comparable habitats. Presumably dust fall is readily washed off the tree needles by rain. Larix concentrates B to a much greater degree than does Sphagnum.