5b. Body of the bur and the spines densely pubescent --6. 6a. Body of the bur more than twice as long as thick; a common weed =Cocklebur, Xanthium commune.= 6b. Body of the bur less than twice as long as thick =Cocklebur, Xanthium echinatum.= 7a. Leaves twice-pinnatifid =Ragweed, Ambrosia artemisiifolia.= 7b. Leaves once-pinnatifid =Ragweed, Ambrosia psilostachya.= 8a. Leaves deeply 3-lobed (1-5 m. high) =Giant Ragweed, Ambrosia trifida.= 8b. Leaves serrate or obscurely lobed --9. 9a. Stem simple or sparingly branched; pistillate heads in the axils of the upper leaves (1-3 m. high) =Giant Ragweed, Ambrosia trifida var. integrifolia.= 9b. Stem much branched; heads all alike, in panicles =Marsh Elder, Iva xanthifolia.= 10a. Flowers all strap-shape; juicy milky. (The central flowers must be examined carefully, since they are frequently much smaller than the marginal ones) --11. 10b. Flowers all tubular, with regular. 4-5-lobed corollas --45. 10c. Flowers both tubular and strap-shape; heads radiate (in a few species the rays are small and may be overlooked by mistake) --108. 11a. Flowers blue (summer and autumn) --12. 11b. Flowers orange, yellow, white, or purplish --15. 12a. Heads 2.5 cm. wide, or larger --13. 12b. Heads 1.5 cm. wide, or smaller --14. 13a. Leaves linear; bracts longer than the flowers, heads 5-10 cm. wide (6-15 dm. high) =Salsify, Tragopogon porrifolius.= 13b. Leaves broader, mostly serrate; bracts shorter than the flowers; heads 2.5-4 cm. wide =Chicory, Cichorium intybus.= 14a. Heads in a narrow crowded cluster (5-15 dm. high) --30b. 14b. Heads in a spreading open panicle (Wild Lettuce) --22. 15a. Heads solitary at the summit of leafless stalks --16. 15b. Heads several, on leafy, naked, or scaly stalks --19. 16a. Basal leaves strictly entire; heads about 2.5 cm. wide (summer and autumn) --35a. 16b. Basal leaves toothed, lobed, or pinnatifid (spring and summer) --17. 17a. Heads 8-14 mm. wide (1-4 dm. high) =Dwarf Dandelion, Krigia virginica.= 17b. Heads 25-50 mm. wide (1-6 dm. high) (Dandelion) --18. 18a. Outer involucral bracts reflexed =Dandelion, Taraxacum officinale.= 18b. Outer involucral bracts erect or spreading =Dandelion, Taraxacum erythrospermum.= 19a. Pappus none; heads about 1 cm. wide (4-10 dm. high; summer) =Nipplewort, Lapsana communis.=