HITCHCOCK AND CHASE—NORTH AMERICAN PANICUM. 21 
First glume very small, not over one-fourth the 
length of the small, obovate, blunt spike- 
let; tropical species. (See also P. repens with 
pointed spikelets)................2---------- See 
First glume as much as one-third the length of the 
spikelet (shorter in P. repens). 
Spikelets pubescent. 
Fruit silky-villous; spikelets 6 to 7 mm. long, 
densely villous. ..........--2----------- 75. 
Fruit smooth and shining; spikelets not over 
3.5 mm. long. 
Culms and sheaths glabrous or softly pubes- 
cent; blades ovate-lanceolate.......... 78. 
Culms and sheaths densely harshly villous; 
blades linear...................2-.----- 80. 
Spikelets glabrous. 
Sterile palea enlarged and indurated at ma- 
turity, expanding the spikelet; blades 
scarcely wider than their sheaths. 
Spikelets 3 mm. long, congested; panicles 
dark purple. .....................-.-. 63. 
Spikelets not over 2.4 mm. long; panicles 
green or pale. 
Panicle branches spikelet or branchlet- 
bearing along the upper half or toward 
the ends only.......-.-.-.---------- 62. 
Panicle branches’ branchlet - bearing 
throughout their length or nearly so. 61. 
Sterile palea, if present, not enlarged and 
indurated. 
Plants forming conspicuous creeping, scaly 
rootstocks. 
Spikelets long - pediceled, not secund, 
arranged in open or contracted 
panicles .......2..-..----+----------- See 
Spikelets short-pediceled, more or less se- 
cund along the nearly simple panicle 
branches. 
Panicles open; spikelets 3.4 to 3.8 
mm. long (shorter in exceptional 
specimens) .........-----.-2-2---- 50. 
Panicles more or less contracted; spike- 
lets not over 2.8 mm. long........- 56. 
Plants not forming creeping, scaly rootstocks. 
Fruit crested at the apex; spikelets 5.5 to 
- 
6 mm. long; tropical species........-. 195. 
Fruit not crested. 
PARVIGLUMIA, 
p. 124, 
P. urvilleanum. 
P. millegrana. 
P. rudgei. 
P. cupreum. 
P. hians. 
P. exiguiflorum. 
Viraata, p. 84. 
<+ 
P. anceps. 
P. rhizomatum. 
P. zizanioides. 
