 Some cultivated specimens are grafted on rootstocks of "Fraxinus excelsior", with an often very conspicuous change in the bark at the graft line to the fissured bark of the rootstock species.A sugary extract from the sap may be obtained by making a cut in the bark; this was compared in late medieval times (attested by around 1400 AD) with the biblical manna, giving rise to the English name of the tree, and some of the vernacular names from its native area ("fresno del maná" in Spanish, "frassino da manna" in Italian).In fact, the sugar mannose and the sugar alcohol mannitol both derive their names from the extract.