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Key to Xanthium
https://fsus.ncbg.unc.edu/main.php?pg=show-key.php&keyid=40641
2 Leaves pinnatifid to bipinnatifid, about 2× as long as wide; leaf pubescence of silvery hairs on both sides; decumbent annual 20-30 cm tall; burs woolly-hairy | |
2 Leaves simple or trilobed, 3-4× as long as wide; leaf pubescence of silvery hairs on the lower surface and strigose hairs on the upper surface; erect to decumbent annual to 50-100 cm tall; burs only lightly hairy | |
5 Burs generally glabrous or puberulent, usually light tan at maturity; burs 1.0-2.0 (-2.5) cm long (including the beaks); prickles mostly straight, hooked prickles restricted to the upper portion of the bur; beaks straight | |
6 Beaks glandular-puberulent; upper stem sparsely strigose; [more widespread in distribution and habitat] |