Dutchman's Breeches (Dicentra cucullaria)
Dutchman's Breeches flowers (Dicentra cucullaria) growing in a hardwood forest at Lake Goede State Park in Iowa.

Details:  Canon EOS 10D,  shutter 1/60 second, aperture f8, ISO 100, Promaster 100 mm macro lens, no flash
 

Selected References:

Thieret John W, Niering William A, and Olmstead Nancy C. National Audubon Society Field Guide to North American Wildflowers, Eastern Region. New York: Alfred A. Knopf, Inc. Plate 124, P 552.