HITCHCOCK AND CHASE—NORTH AMERICAN PANICUM. 209 
Autumnal form ascending or spreading, 
branching from middle and upper 
nodes; the reduced, fascicled blades 
strongly ciliate. 
Culms 40 to 70 cm. high, autumnal 
culms usually 40 to 50 cm. long; 
southeastern U. S..........2.... 126. P. lanuginosum. 
Culms 20 to 40 cm. high, autumnal 
culms usually 20 to 30 cm. long, 
the early branches zigzag; West 
Indies......-........-22----20-- 127. P, acuminatum. 
Plants pubescent, often villous, but not velvety. 
Culms conspicuously pilose with long, horizontally 
spreading hairs; branching before expansion of 
primary panicles.............-.-.------+---- 131. P. praecocius. 
Culms variously pubescent, if pilose the hairs not 
long and horizontally spreading. 
Vernal blades glabrous or nearly so on the upper 
surface, firm in texture. 
Autumnal culms branching from the lower 
nodes, forming a spreading bunch 10 
to 15 em. high; Pacific slope......... 133. P. occidentale. 
Autumnal culms branching from the middle 
nodes, forming widely spreading mats; 
Atlantic slope (see also form of P. hua- 
chucae silvicola)........--+---+-+--+-++- 125. P. tennesseense. 
Vernal blades pubescent on upper surface, some- 
times pilose near base and margins only. 
Spikelets 1.3 to 1.5 mm. long; vernal blades 
long-pilose on upper surface. 
_Autumnal form widely decumbent- 
spreading, forming a mat; vernal 
culms soon geniculate-spreading; 
plants olivaceous..............-- 122. P. albemarlense. 
Autumnal form erect or leaning, never 
forming a mat; plants yellowish- 
green. 
Axis of panicle pilose, panicle 
branches tangled, the lower 
drooping..-.......---.------ 123. P. implicatum. 
Axis of panicle puberulent only, 
panicle branches not tangled, 
the lower ascending......-.--- 121. P. meridionale. 
Spikelets 1.6 to 2 mm. long; vernal blades 
pilose or pubescent. 
Upper surface of blades pilose; spike- 
lets 1.8 to 2mm. long; autumnal 
form decumbent-spreading. 
Spikelets pointed; culms weak and 
lax.......0222.2-2----+------ 136. P. languidum. 
Spikelets obtuse; culms not weak 
and lax. 
41616°—vo.t 15—10——14 
