Fleance, Banquo's son, symbolizes Macbeth's crown to be "fruitless" due to him being in the witches' prophecy. The prophecy explains how Macbeth becomes king, which becomes reality, however, the witches also declare that Banquo's descendant will become king. The fact that Fleance escaped Macbeth's assassination plans causes Macbeth to become uneasy, and he states that "Upon my head they placed a fruitless crown And put a barren sceptor in my grip, Thence to be wrenched with an unlineal hand," (3.1.65-68). This quotation directly refers to Macbeth's fears about Fleance becoming king, and additionally directly states "fruitless crown", proving the fruitless crown to be a significant symbol. Therefore, Macbeth becoming paranoid about Fleance taking his crown displays how his mental health declines throughout the play.