These are the lines from Macbeth's soliloquy, "Upon my head they placed a fruitless crownAnd put a barren scepter in my grip,Thence to be wrenched with an unlineal hand,No son of mine succeeding. <span>"
His kingship is in the threat of Banquo since he doesn't have a son to pass on his throne while Banquo has.</span>
