To study the bryophyte flora of Thuja seedbed logs in Reeses Bog, Michigan, two independent sampling procedures were necessary. The purpose of the first survey was to determine germination site preferences of Thuja seedlings, and a second survey was done to determine the characteristic bryophyte flora of the most suitable site for seedling germination. Of the 1800 Thuja seedlings counted in the first sruvey, over 70 percent were found on logs in various stages of decay. In the second survey the bryophyte flora of 80 logs with seedlings present was sampled. It was found that over 90 percent of these logs were in the middle stages of decay. Bryophytes were found to cover an average of nearly 90 percent of the upper surfaces of these logs. No seedlings were found on logs without some bryophyte cover. The bryophyte species most important in Thuja seedling establishment were found to be pleurocarpous, mat-forming plants such as Heterophyllium haldanianum, Pleurozium schreberi, and Brotherella recurvans. It is proposed that the major role of bryophytes in Thuja seedling establishment lies in the provision of a suitable microenvironment for seed germination.