What are these bumps on collard greens? (Sorry, no pictures)

[Dennis S]

I saw them on a bunch at the store so I got a different bunch. It turns out it had some too. They're a little smaller than a BB, but irregularly shaped. They stick up a little but then are flat on top, like a butte. They look like the would peel off but get smushed when you try. I couldn't find anything on Google.