Fern

A bishop's crozier is said to be a fancied-up shepherd's crook, but most croziers look more like this- a fern frond on the point of unfurling. And a fern frond on the point of unfurling, when you come to think of it, looks a lot like a vortex, which looks a lot like a spiral galaxy. Symbolism is never a matter of A=B, but more like A=B=C... and when one alphabet runs out you start on another...