Who says you must up-fill this osier cage of ours in romeo and Juliet?

Juliet says this when she is talking to Romeo from her balcony in Act II, Scene 2 of Romeo and Juliet. She is telling him that their love is forbidden, and that if they are ever caught together, they will be punished. She asks Romeo to leave her, saying, "But love and peace will make thee worthy thereof. Then, dearest Peregrine, bid adieu to this osier cage of ours, and wander free in heaven's wide wilderness.