HITCHCOCK AND CHASE—NORTH AMERICAN PANICUM. 143 
Spikelets not turgid, blunt, nor strongly nerved (see, 
however, P. roanokense and P. caerulescens.) 
Ligule of conspicuous hairs, usually 3 to 5 mm. 
long. 
Sheaths glabrous or only the lowermost some- 
NUM AU MOTO ESCE MURS saa aver eles i Oa Vee @-SPRETA (p. 200). 
Sheaths strongly pubescent..............-.- ©. Lanueinosa (p. 208). 
Ligule obsolete or nearly so (manifest in P. vis- 
cidellum, P. oricola, P. tsugetorum and P. cur- 
tifolium.) 
Spikelets spherical at maturity; blades glabrous, 
firm, cordate; plants sparingly branching S.SPHAEROCARPA ce 250). 
Spikelets usually obovate or elliptic. 
Blades of mid-culm elongated, less than 1.5 cm. 
wide; culms usually tall; spikelets pointed, 
abruptly so in the velvety P. scoparium 
ainGl 12s DOSGIC UMM DSM we ca) ahs ieee \4.. Scoparia (p. 294), 
Blades of mid-culm not elongated (somewhat so 
in P. equilaterale). 
Blades cordate, 1 to 3 cm. wide (5 to 12 mm. 
in P. ashev); spikelets pubescent. 
Spikelets 2.5 to 3 mm. long; sheaths 
glabrous or minutely puberulent. .$.Commutata (p. 300). 
Spikelets 3 to 5 mm. long (sometimes but 
2.7 mm. long in the hispid-sheathed 
IP clamadestinunm saan scheme tae \G. .LATIFOLIA p. (312). 
nota Blades not cordate, less than 1 em. wide. 
AR ts Se i ‘ ssed - : 
ae ss Sheaths crisp or appressed - pubescent; 
Pe Coes blades firm; spikelets pubescent. .§..COLUMBIANA (p. 240). 
eo aS Sheaths glabrous (sparsely pilose in P. 
curtyfolium and the lower, velvety 
in P. mattamuskeetense). @ 
Vernal culms delicate (sometimes scarcely 
so in P. albomarginatum and P. 
tenue); spikelets 1.5 mm. or less 
long (1.6 to 1.7 mm. in P. tenue)\QEnsrrouta (p. 258). 
Vernal culms slender but not delicate, 
rarely less than 40 cm. high; spike- 
lets 2 to 2.9 mm. long (1.5 mm. in 
P. microcarpon and P. caerulescens). 
Lower internodes shortened, upper 
elongated, producing a_ nearly 
naked culm, leafy at base; spike- 
lets narrowly ovate, 2.7 to 2.9 
MRT | LOM SEP ee ose UN NuDICAULIA (p. 179). 
Lower internodes not shortened; 
vernal culms about evenly 
leafy throughout, spikelets el- 
liptic or obovate, not over 2.5 
pa LONG. eles eu os detec lse,: ae DEOHOTOMA (p./1'79). 
Se EN en As2 Ne as i 
niin mies cures Uru tetsine 
