Barnacle goose were of the same nature as other birds. The question of the nature of barnacle geese also came up as a matter of Jewish dietary law in the Halakha, and Rabbeinu Tam (1100–71) determined that they were kosher (even if born of trees) and should be slaughtered following the normal prescriptions for birds. The mythical barnacle tree, believed in the Middle Ages to have barnacles that opened to reveal geese, may have a similar origin to the other legends already mentioned. Barnacle goose The barnacle goose ("Branta leucopsis") belongs to the genus "Branta" of black geese, which contains species with
Genus of a quadratic form the same genus have equal discriminant and hence there are only finitely many equivalence classes in a genus. The Smith–Minkowski–Siegel mass formula gives the "weight" or "mass" of the quadratic forms in a genus, the count of equivalence classes weighted by the reciprocals of the orders of their automorphism groups. For binary quadratic forms there is a group structure on the set "C" equivalence classes of forms with given discriminant. The genera are defined by the "generic characters". The principal genus, the genus containing the principal form, is precisely the subgroup "C" and the genera are the cosets of "C":