Helmet Flower, a native species, has been added to the USWildflowers database (08/09/2010.)  Scientific name is Scutellaria integrifolia.  This plant also is known by the common names Hissopleaf Skullcap, Helmet Skullcap, and Hyssop Skullcap.  Photo below was taken at the Chickamauga National Military Park in GA on  05/31/2010.

Helmet Flower - Scutellaria integrifolia