Common lambsquarters, Chenopodium album, seeds.

Five spiky, oval burrs with white spines are spread out on a gray background, with a scale indicating 1 mm for size reference. The burrs are around 3 mm in length. Copyright information is at the bottom (Copyright 2007 The Regents of the University of California. All rights reserved.). Credit: James A. O'Brien, University of California
Credit: James A. O'Brien, University of California