My huckleberry branches are growing through these.
Is it a fungus? Is it some kind of tumor?
these grow wild around my cabin in southcentral alaska
leaves appear to be incorporated into the thing.
here is a cross-section of the thing.
Just on the basis of a little websearching, I'm going to guess hackberry petiole gall:
Florida's website had it right by labeling it a "featured creature" - pretty darned interesting if you like that sort of thing, and harmless either way. It seems to me that hackberries have more galls than even their closest competition, aspen or maybe oak.