The rhizoid-tuber-bearing mosses, Bryum tenuisetum and B. violaceum, have been found on Nantucket Island, Massachusetts, on acidic sandy soil in areas of anthropogenic disturbance. Neither one has evidently been reported before for New England, and they are known only from a few places elsewhere in eastern North America. The plants of B. violaceum had strongly papillose rhizoids (vs. smooth according to descriptions of plants from elsewhere) but agree with other collections in various diagnostic characteristics. Plants in both collections were without sporophytes, which is typical of these dioicous bryums.