In Wales the necessity for settlement did _not_ generally produce the three-field system _with holdings in yard-lands_,[630] because, as the Welsh tribesmen, though they may have had household slaves, as a rule held no taeogs or prædial slaves, it produced no serfdom. But under the German tribal system, even in the time of Tacitus, the tribesmen in the [p414] semi-Romanised districts, at all events, already had prædial slaves. «The Roman villa another factor and grew into the manor.» The manorial system, however, was not simply a development from the tribal system of the Germans; it had evidently a complex origin. A Roman element also seems to have entered into its composition. The Roman _villa_, to begin with, a slave-worked estate, during the later empire, whether from German influence or not, became still more like a manor by the addition of _coloni_ and other mostly barbarian semi-servile tenants to the slaves. There may have been once free village communities on the 'ager publicus,' but, as we have seen, the management of the public lands under the fiscal officers of the Emperor also tended during the later Empire to become more and more manorial in its character, so much so that the word 'villa' could apparently sometimes be applied to the fiscal district. «Roman and German elements combined.» Whichever of the two factors--Roman or German--contributed most to the mediæval manor, the manorial estate became the predominant form of land ownership in what had once been Roman provinces. And the German successors of Roman lords of villas became in their turn manorial lords of manors; whilst the 'coloni,' 'liti,' and 'tributarii' upon them, wherever they remained upon the same ground, apparently became, with scarcely a visible change, a community of serfs. «Both 'ager publicus' and 'terra regis' manorial.» On the other hand, the fact that the _terra regis_ also was divided under Saxon and Frankish kings into _manors_ probably was the natural result of the growing manorial management of the public lands under the fiscal officers of the Emperor during the later Empire, [p415] quickened or completed after the barbarian conquests. The fiscal districts seem to have become in fact royal manors, and the free 'coloni,' 'liti,' and 'servi' upon them appear as manorial tenants of different grades in the earliest grants to the monasteries. The fact that as early as the time of Tacitus, the German chieftains and tribesmen were in their own country lords of serfs, in itself explains the ease with which they assumed the position of lords of manors on the conquest of the provinces.