Straw, R.M. 1966. A redefinition of Penstemon (Scrophulariaceae). Brittonia. 18(1): 80-95.
Straw, R.M. 1966. A redefinition of Penstemon (Scrophulariaceae). Brittonia. 18(1): 80-95.
Western Forbs
Straw, R.M. 1966. A redefinition of Penstemon (Scrophulariaceae). Brittonia. 18(1): 80-95.