154 Paniceae Panicum 



Culms and sheaths with a spreading pubescence; ligules about 1 mm 

 long; spikelets bluntly obovate, mostly 3-3.5 mm iong and 2 mm 



■wide 43. P. Scribnerianam, p. 171. 



Spikelets less than 3 mm long. 



Sheaths retrorsely pilose 14. P. xalapense, p. 161. 



Sheaths not retrorsely pilose. 



Basal leaves like those of the culm; plants not forming winter rosettes. 



Spikelets 1.8-2.3 mm long; fruit not stalked 9. P. agrostoides, p. 159. 



Spikelets 2.4-2.8 mm long; fruit with a basal stalk 0.2-0.4 mm long. 



8. P. stipitatum, p. 159. 



Basal leaves not like those of the culm; plants forming winter rosettes B. 

 B (to left to save space). 

 B. Culms glabrous or only the nodes pubescent. 



Ligule more than 1.5 mm long; spikelets 1.3-1.6 mm long. 



Panicles narrow, a fourth to a third as wide as long (somewhat wider in anthesis) ; 



spikelets elliptic 22. P. spretum, p. 164. 



Panicles open, two thirds as wide as long or longer; spikelets obovate 



23. P. Lindheimeri, p. 164. 



Ligule less than 1.5 mm long; spikelets 1.4-2.9 mm long. 

 Spikelets 1.4-1.7 mm long. 



Nodes of culms usually copiously barbed with long, lax, retrorse hairs; at 

 least the lower sheaths more or less marked with white spots between the 

 nerves; leaves usually glabrous, 6-14 mm wide, spreading or the upper 



reflexed 16. P. microcarpon, p. 162. 



Nodes of culms minutely appressed-pubescent. 



Upper three blades usually 10-20 cm long and 25 mm wide, the upper blade 

 usually not much smaller than the other two, the blades below the upper 



three usually much smaller; anthers mostly 0.4-0.5 mm long 



39. P. polyanthes, p. 170. 



Upper three blades usually 5-10 cm long and 7-14 mm wide, the upper one 

 usually much reduced, the blades below the upper three usually not 

 reduced; anthers mostly 0.6-0.8 mm long. . . .40. P. sphaerocarpon, p. 170. 

 Spikelets 1.8-2.9 mm long. 

 Spikelets 1.8-2.2 mm long. 



Culms soon decumbent and trailing, the nodes usually glabrous or the lowest 

 with a few soft spreading hairs; vernal blades spreading, mostly 4-6 mm 



wide; plants of a wet habitat 20. P. lucidum, p. 163. 



Culms erect, never trailing; vernal blades erect or spreading, mostly 4-14 mm 



wide. 



Vernal blades mostly 4-8 mm wide, rarely some of them wider ; lower part of 



culms usually more or less geniculate; lowest nodes of culms usually 



more or less barbed with soft hairs; plants usually of a dry habitat, 



often reclining in the autumnal phase and the nodes glabrous 



17. P. dichotomum, p. 163. 



Vernal blades mostly 6-14 mm wide, more erect; culms not geniculate and 

 the nodes usually all glabrous or with only a few soft hairs on the 



lowest; plants of a wet habitat 19. P. boreale, p. 163. 



Spikelets 2.3-2.9 mm long. 



Blades mostly less than 8 mm wide, glabrous on both surfaces, not cordate 



at the base; spikelets oblong-elliptic, 2.3-2.9 mm long 



15. P. Bicknellii, p. 162. 



Blades mostly 8-12 mm wide, cordate at the base, usually pubescent or the 



upper surface glabrous; spikelets elliptic, about 2.5 mm long 



18. P. mattamuskeetense, p. 163. 



B. Culms and sheaths more or less puberulent to strongly pubescent. 

 C. Ligule 2 mm or more long. 



Plants grayish velvety-pubescent; spikelets 1.3-1.4 mm long 



24. P. miburne, p. 166. 



