Black crowberry. Empetrum nigrum. Crowberry Family. Fruit. — The black drupe is berrylike, globular, and incloses six to nine seedlike nutlets with a seed in each. The calyx is at the base and the stigma is at the apex. The drupes are solitary in the leaf axils. They are juicy, acid, edible, and serve as food for the Arctic birds.
Source: wiktionary