Via Dappled Things, a wonderful essay at Pontificaitons examining branch theory. An excerpt below, please go and read the whole thing.
Fr. Gregory Mathewes-Green on Pontifications
First, the fact that Anglicanism has fallen into heresy and apostasy is itself evidence that, even if the branch theory were valid, Anglicanism is not and was not one of the branches—probably not since the East-West split and certainly not since the Reformation. A community’s apostolicity is evidenced in that it continues to hold the apostolic Faith. There may be from time to time theological ferment and heated doctrinal debate, but when the time comes for decision making, that community which is apostolic insists on fidelity to that received Tradition. Anglicanism is presently not such a community.