Edited by Minnesota Scientific and Natural Areas, some rights reserved (CC BY-SA)
Photo Credits
- 1. (c) manual crank, some rights reserved (CC BY-NC-SA)
- 2. (c) Frank Mayfield, some rights reserved (CC BY-SA)
- 3. (c) judith holm, some rights reserved (CC BY-NC-ND), uploaded by judith holm
- 4. (c) Susan Elliott, some rights reserved (CC BY-NC), uploaded by Susan Elliott