Cool!
Suspect they are galls due to insects laying eggs in the leaf. If so, when you cut one in half, you're likely to see the youngsters.

Please cut & post an image of whatever you find.

Oh yes, in most cases, insect galls don't damage the plant's health. But 1st, let's see what's in one of the bumps.

Surgery? OK, I'll check it out tomorrow. Silly me, I was just going to cut the whole thing off and not check to see what was inside. Not much light left today, though, so stay tuned tomorrow.

I cut the branch off, then I cut a few of the galls open, but I didn't see anything inside but a small void. They seemed smaller than they were the other day, though, so maybe whatever was there had already departed. If I see them again, I'll deal with them more promptly.

Here is a link that might be useful: Well That Was Anticlimactic