Columella in his Res Rustica always speaks of the bailiff (uilicus) as the slave of the owner of the farm, but in his Preface he states that the owner sometimes sent a mercenarius to be bailiff, and this has by some scholars been taken to mean that a freeborn labourer could be appointed. Since such a possibility is not mentioned by Columella elsewhere or by any other Roman writer, it is probable that the term mercenarius in the Preface has been misunderstood. Hired labourers in ancient Rome included slaves as well as freemen.