Ballhead Waterleaf, a native species, has been added to the USWildflowers database (06/18/2010.)  Scientific name is Hydrophyllum capitatum.  A variety of this plant also is known by the common name Alpine Waterleaf.  Photo below was taken Boise National Forest near Boise, Idaho on 06/15/2010.

Ballhead Waterleaf - Hydrophyllum capitatum