Tribune was acknowledged by the patricians, thereby creating a legitimate assembly of plebeians (Concilium Plebis). After 494 BC, a plebeian tribune always presided over the Plebeian Curiate Assembly. This "Plebeian Curiate Assembly" was the original Plebeian Council, which elected the plebeian Tribunes and Aediles, and passed legislation (plebiscita) that applied only to the plebeians. From 471 to 27 BC During the later years of the Roman Kingdom, King Servius Tullius enacted a series of constitutional reforms. One of these reforms resulted in the creation of a new organizational unit, the tribe, to assist in the reorganization of the army. Its divisions were not ethnic (as the divisions of the Curia were), but rather geographical. Tullius divided the city into four geographical districts, each encompassing a single tribe. Between the reign of Tullius and the late 3rd century BC, the number of tribes expanded from 4 to 35. By 471 BC, the plebeians decided that organization by tribe granted them a level of political independence from their patrician patrons that the curiae did not. Therefore, around 471 BC, a law was passed to allow the plebeians to begin organizing by tribe. Thus, the "Plebeian Curiate Assembly" began to use tribes, rather than curiae, as its basis for organization. As such, the Plebeian Council changed from a "Plebeian Curiate Assembly" to a "Plebeian Tribal Assembly". The only difference between the Plebeian Council after 471 BC and the ordinary Tribal Assembly (which also organized on the basis of the tribes) was that the tribes of the Plebeian Council included only plebeians, whereas the tribes of the Tribal Assembly included both plebeians and patricians. However, most Romans were plebeians. Therefore, the principal differences between the Plebeian Council and the Tribal Assembly were mostly legal rather than demographic. These legal differences derived from the fact that Roman law did not recognize an assembly consisting only of one group of people (plebeians in this case) from an assembly consisting of all of the People of Rome. Over time, however, these legal differences were mitigated with legislation. The Plebeian Council elected two plebeian officers, the tribunes and the aediles, and thus Roman law classified these two officers as the elected representatives of the plebeians. As such, they acted as the presiding officers of this assembly. The plebeians, through the Plebeian Council, began to gain power during this time. Two secessions in 449 BC and 287 BC brought