Leather Vasevine, a native species, has been added to the USWildflowers database (07/27/2010.)  Scientific name is Clematis viorna.  This plant also is known by the common names Leather Flower and Vasevine.  Photo below was taken along the Blue Ridge Parkway near the Pisgah Inn, on 07/12/2010.

Leather Vasevine – Clematis viorna