Pixie cups

This is neither a plant nor a mushroom, though when I was a boy it would have been thought to be a kind of plant. It's a lichen. The cups are about a half-centimeter high.

I was out in the rain and three-degree weather today and saw a lot of these. I thought they were probably Cladonia of some sort, but didn't know which until I asked on a local fungi-discussion page. Pixie cup lichen (C. asahinae), it is.