M. Tullius Cicero De Lege Agraria 26

1.
  The comitia curiata, at which alone a lex curiata could he passed, was a meeting of the populus of Rome , assembled in its tribes of houses; and no member of the plebs could vote at such a meeting. They met principally for the sake of confirming some ordinance of the senate; a senatus consultum was an indispensable preliminary, and with regard to elections and laws, they had merely the power of confirming or rejecting what the senate had already decreed. The lex curiata ( de imperio),which was the same as the auctoritas patrum, was necessary in order to confer upon the dictator, the consuls, and the other magistrates the imperium or military command. The comitia curiata were held by the patrician magistrates, and they voted by their curies.
  The comitia centuriata were the assembly of the populus and plebs together, and they voted by their centuries by ballot.
  The comitia tributa were not established till B. C. 491. They were an assembly of the people according to the local tribes into which the Plebs was originally divided. No qualification of birth or property was necessary to enable a them to vote in the comitia tributa. They were summoned by the tribuni plebis, who were also the presiding magistrates in general; but the consuls or praetors might preside if they were convoked for the election of inferior magistrates, such as the quaestor, propraetor, or proconsul. Smith, Dict. Ant. p. 274, v. Comitia, q. v.

2. This and the preceding chapter are exceedingly obscure, and almost unintelligible to us; perhaps also the text is a little corrupt. Manutius says, “An exceedingly difficult passage, which has perplexed men of the greatest ability and learning.” His explanation is as follows: “The ancient Romans had chosen that the people should decide on the election of every magistrate in two comitia; but the magistracies are distinguished into patrician and plebeian; the patrician magistrates are the quaestor, the curule aedile, the praetor, the consul, and the censor; the plebeian are the tribune of the people, the aedile of the people, and others. But there were two comitia first about the patrician magistrates before the plebeian ones were elected, namely the centuriata comitia, and the curiata. I except the censors, who, although they were patrician magistrates, still were elected by one comitia only, the centuriata. But when the plebeian magistrates were elected, then the tributa comitia succeeded to the place of the curiata, for the curiata had nothing to do with the plebeian magistrates. For they were instituted for the sake of the patrician magistrates long before the origin of the plebeian ones. Some one may say, Why were not the centuriata taken away for the same reason, as they were instituted by king Servius when there were not yet any plebeian magistrates? The answer is, In order that there might be some comitia held with proper auspices at which the patrician magistrates might be created, for the auspices were not taken at the tributa comitia. As, therefore, in the case of the patrician magistrates, (with the exception, as I have said before, of the censor,) the people gave their votes first in the centuriata comitia and then in the curiata, before the plebeian magistrates were elected; so, when the plebeian magistrates were elected, the same people voted in the centuriata and tributa comitia.”