Scar

It is a wet drizzzley day today and again I haven't been out further than the yard.  I have looked at this scar on this tree for a long time. It is the remnants of a branch cut off a hackberry a couple of years ago. The branch was in great danger of being blown off in a high wind and blocking the drive. But what is left in the scar intrigues me. The very thick band must have been inside the bark, but is it all phloem? or is there an inner bark made up of some other sort of cells? The wood in the center is clear enough with its annual rings and the heartwood is dead and has cracked. I need help. I am so out of date and have forgotten so much!