This warty looking growth on what I think is an Elm is a burl. Burls are thought to be caused by the tree being stressed by some invading insect or virus. What ever the cause, the timber that lurks beneath that lumpy bark is utterly beautiful. If you own or have glimpsed the interior of very expensive British car like the Royal family frequent, you may be familiar with the wood panelling on the dashboard, quite often it is a veneer of Elm burr (burl). Many different species can produce burls. Sometimes I have found our native Beech tree burls washed up on a West Coast beach. I did find an Elm burl that someone had dumped on a river bank. After a gut busting struggle I managed to squeeze it into the back of the station wagon. Once I got it home I weighed it on the bathroom scales. Sadly this was the last thing they ever weighed. It was over 120 kg. Sadly I kept it on the ground and rot and borer consumed most of it.