This is what I saw when I cut the root zone off. A real ugly mess. Oddly, though, this fungus was not of the slimy variety. Everything was quite dry. Note that the plant is trying to live. It's sending new roots (I see three) out the middle of the rotten zone, which is where whatever remnant of the vascular bundle that has survived would be. The green edge made me believe that maybe this plant can be saved.