348 The Ohio Naturalist. [Vol. XIV, No. 8, 



11. Spikelets 3^ inch long or more. 12. 



11. Spikelets less than J^ inch long, usually about re inch. 22. 



12. Leaves less than j^ inch wide and about 18 times as long as wide. 



Paniciim depauperatnm. (10). 



12. Leaves more than 3-:4 inch wide, and not elongated. 1.3. 



13. Upper surface of the leaves glabrous. 14. 



13. Upper surface of the leaves pubescent. Panicum leibergii. (24). 



14. Outer empty glume \ as long as the spikelet. short acute. 



Panicum scrihnerianum. (25). 



14. Outer empty glume J^ as long as the spikelet, long acuminate. 



Panicum xanthophysum. (26). 



15. Stem siinple or with basal branches only. 16. 



15. Stem at length faciately branched. 22. 



16. Hairs on the leaf sheath almost an 3^ inch long or longer, spreading, 



usually dense. Panicum linearifolium. (11). 



16. No hairs on the leaf sheath, or with hairs less than j^ inch long, 



sometimes ciliate on the margin. 17. 



17. Leaf blade xs inch or less wide, usually 18 or more times as long 



as wide; spikelets usually glabrous. 18. 



17. Leaf-blade usually much more than 34 inch wide, never more than 



8 times longer than wide; spikelets more or less pubescent. 20. 

 IS. Leaves much elongated; often 6 to 10 inches long, attenuate at the 

 base. Panicum zverneri. (12). 



18. Leaves not elongated; generally less than 33^ inches long, not at- 



tenuate at the base, spikelet less than }/$ inch. 



Panicum bicknellii. (13). 



19. Spikelets roundish, not over j^ inch long. 20. 



19. Spikelets oblong-eliptic oreliptic, usually j^ inch or more long. 21. 



20. Nodes pubescent with appressed hairs, base of the leaves ciliate, 



panicle nearly as wide as long. Pafiicum sphaerocarpon. (14.) 



20. Nodes glabrous, base of the leaves not ciliate, panicle not more than 



3^2 wide as long. Panicum polyanthes. (15). 



21. Stems pubescent. Panicum- tsugetorum. (23). 



21. Stems glabrous. Panicum horeale. (18). 



22. Spikelets glabrous. 23. 



22. Spikelets pubescent. 24. 



23. Nodes densely bearded. Panicum microcurpon. (17). 



23. Nodes not bearded. Panicum dichotomum. (16). 



24. Ligule at the top of the leaf sheath minute or al^sent. 25. 



24. Ligule present. 26. 



25. Nodes of the main stein glabrous or with a few hairs. 



Panicum boreale. (18). 



25. Nodes of the main stem crisp pubescent. 



Panicum ashei. (27). 



26. Upper sheaths glalirous (ciliate on the margin). 



Panicum lindheimcri. (19). 



26. All of the sheaths pubescent. 27. 



27. Upper surface of the leaves glabrous, except for a few long hairs 



near the base. Panicum tsugetorum. (23). 



27. Upper surface of the leaves pilose. 28. 



28. Outer empty glume acute; spikelet xe inch long pubescence on the 



sheath more than xg- inch long. Panicum. viUosissimum. (21). 



28. Outer empty glume blunt; spikelet less than -^ inch long; pubes- 



cence on the sheaths not so dense and less than j^ inch long. 29. 



29. Upper surface of the leaf-blade long-pilose; plants yellowish-green. 



Panicum hauchucae. (20). 

 29. UpiK'r surface of tlie leaf-blade long-appressed i)ul)escent. 



Panicum im plicatum. (22). 



