Rock clematis (Clematis Columbiana)

My wife Joan found these on the Lily Pad Lake trail in late June, 2010. They seem to be somewhat rare up here.

Late June, 2014. There are very many of them on the Angler Mountain Trail. We saw a few a few days earlier on the Lily Pad Lake Trail, but not as many as in 2010.

The next image is from June 23, 2015, taken with new lens and camera. They were very abundant on the Angler Ranch Trail north of Silverthorne.