old dead wood from a tree stronger than any other wood from that tree?

Explanations I don't have, but it's well known that locust wood (commonly known as "ironwood") can be fairly easily cut when green, but is some of the toughest wood in the world after curing. If you have a locust tree come down in your yard, you'd be wise to cut it up immediately. After as little as a few weeks it may be hard enough to wear out a chain saw. You can hurt yourself, even break a bone, trying to cut cured locust limbs with a sharp axe (just bounces off). Locust fence posts commonly last MUCH longer in the ground than will pressure treated pine or fir. Greatly preferred by farmers, but they ALWAYS cut the wood while it's green. Otherwise, it's for the landfill.

Mark 'Sporky' Staplet>

Dry wood is stronger than green wood. Go look it up in the authoritative Wood Handbook, which you can find online chapter by chapter as free downloadable .pdf files. See chapter 4 on mechanical properties.

Pittsburgh Pete

The strongest tissue is always the sclerenchyma, those cells of the tree whose purpose is to strengthen and stabilize. Technically, sclerenchyma cells are 'dead', in that moisture has migrated from the cell leaving only the lignan (hence, 'lignification') behind.

Dave

Thanks for the information. I will keep it in my notes file, who knows it may come useful in future.

Say, you would not know whether animal bodies have a cell which produces the strongest and stabilizing form that is the analogy to sclerenchyma???

Archimedes Plutonium