![](http://www.alamy.com/thumbs/6/F862E179-1572-4ECF-809B-B4953C65FB57/RD3GYG.jpg)
. Day length and crop yields. Plants; Crop yields; Plant photoperiodism. . Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Parker, M. W. (Marion Wesley), 1907-; Borthwick, H. A. (Harry Alfred), 1898-. Washington, D. C. : U. S. Dept. of Agriculture
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Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpublisherwashingtondcusd, booksubjectplants