anicum Paniceae 155 



Plants pubescent, often villous but not velvety. 

 Culms conspicuously pilose with long horizontal hairs, branching before the 



expansion of the primary panicles; spikelets mostly 1.8-1.9 mm long 



25. P. praecocius, p. 166. 



Culms vai-iously pubescent, if pilose the hairs appressed or widely spreading; 

 culm not branching before the expansion of the primary panicles. 

 Spikelets less than 2 mm long. 



Vernal blades glabrous or nearly so above, 6-10 cm long and 5-10 mm wide. 



26. P. tennesseense, p. 166. 



Vernal blades pubescent above or, if glabrous, smaller than the preceding, 

 sometimes pilose above near the base and margins only. 

 Spikelets 1.3-1.5 mm long. 



Upper surface of blades puberulent as well as long-villous 



27. P. albemarlense, p. 166. 



Upper surface of blades villous but lacking the short, appressed 

 puberulence. 

 Axis of panicle pilose, the lowest branches widely spreading; 



spikelets 1.5 mm long 28. P. implication, p. 166. 



Axis of panicle puberulent only, the lowest branches ascending; 



spikelets 1.3-1.4 mm long 29. P. meridionale, p. 167. 



Spikelets 1.6-1.9 mm long. 

 Pubescence on upper surface of vernal blades short-pilose, appressed 

 at least on the apical half; first glume about a third the length of 

 the spikelet, blunt or acute. 



Blades stiff, erect 30. P. huachucae, p. 167. 



Blades lax, spreading. . .30a. P. huachucae var. fasciculatum, p. 168. 

 Pubescence on upper surface of vernal blades long-pilose, ascending; 



first glume about half as long as the spikelet, acuminate 



31. P. subvillosum, p. 168. 



Spikelets 2-2.4 mm long. 



Upper internodes shortened; leaves approximate, the blades often equaling 



the panicles; pubescence sparse and stiff. . . .32. P. scoparioides, p. 168. 



Upper internodes not shortened, the pubescence usually copious and rather 



silky. 



Culms, sheaths, and lower surface of blades pilose but lacking the short 



pubescence; center of blades not glabrous; spikelets about 2 mm 



long 33. P. villosissimum, p. 168. 



Culms, sheaths, and lower surface of blades puberulent as well as pilose; 



center of blades glabrous; spikelets 2.1-2.4 mm long 



34. P. pseudopubescens, p. 168. 



C. Ligules not over 2 mm long. 



Spikelets nearly spheric at maturity, less than 1.8 mm long. 



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 elliptic or obovoid. 



Blades not cordate at the base, spikelets more than 1.7 mm long except in 

 P. columbianum. 



Spikelets mostly 2.8-2.9 mm long 35. P. Deamii, p. 169. 



Spikelets 2-2.2 mm long 36. P. Addisonii, p. 169. 



Spikelets mostly 1.8-1.9 mm long 37. P. tsugetorum, p. 169. 



Spikelets mostly 1.5-1.7 mm long 38. P. columbianum, p. 169. 



Blades cordate at the base. 



