I do not know how they do it naturally, but in my tank, I cut off branches and prop them. I have has experience that one of the finger wilt from about mid way, and stay that way for a couple of days. Upon inspection, there was a small hole down toward the base and is oozing out rotten tissue. I then frag off the base until I do not see the rotten tissue anymore and start fraging the branches. All healed after 2 weeks.