The following pictures show a burl in a tree. A burl is a greatly abnormal proliferation of xylem production by the vascular cambium. The proliferation is highly localized and that abnormal growth is mediated

Burls from a tree trunk can yield valuable material for custom craft work. Insect infestation and certain types of mold are the most common causes of this condition. Burls yield a highly figured wood.

I guess I am showing my age with this reference. Burl Ives was not only a folksinger he was also a radio personality, acted on Broadway, author of many books. "In 1951, he hit the Top Ten with "On