Nodding Bur Marigold flower (Bidens cernua) growing on the bank of a pond at Big Hollow Recreation Area in Des Moines county, Iowa.

Details:

(Top)  Canon EOS 10D,  shutter 1/180 second, aperture f11, ISO 200, Canon EF 100 mm macro lens, Canon MR-14EX flash on

(Bottom)  Canon EOS 10D,  shutter 1/180 second, aperture f9.5, ISO 200, Canon EF 100 mm macro lens, Canon MR-14EX flash on

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 281, P 378-379.