The aim of this article is to shed new light on the history of the Roman ager publicus in Africa as revealed by the epigraphic Lex agraria of 111 BC. According to some recent commentators, this law refers to the leasing out of state-owned land in Africa in return for an annual rent (pequnia) and also to the farming-out of the right to collect this revenue to private tax-farmers. Against this it is argued that throughout the African part of the Lex agraria the term pequnia refers to the price of formerly public land sold off by the state. It is also argued that the enigmatic expression invito eo quei dabit in line 84 is part of a provision concerning the intervention of a third party on the buyer's behalf. The provision in question prescribes that if the buyer does not pay the price immediately and has not yet offered real security in the form of praedia, any third party willing to fulfil either of these obligations will be permitted to do so, even if the buyer does not want the third party to intervene. We are therefore dealing with an early text concerning unsolicited intervention on behalf of a debitor invitus, a topic that is also dealt with in D. 46,3,53 (Gaius) and in D. 17,1,53 (Papinian).