Family POACEZ 49 
2. Phalaris canariensis L. ; Canary-grass. 
Introduced, not common. Alliance; Lincoln; Minden; Valentine. 
Tribe 6. PANICE. 
Spikelets without an involucre. : 
Spikelets not in one-sided spikes. 1. Panicum. 
Spikelets in one-sided spikes. 
Empty scales awned or awn-pointed. 2. Echinochloa. 
Empty scales not awned. 
Spikelets not much longer than wide. 3. Paspalum. 
Spikelets about twice as long as wide. 4. Syntherisma. 
Spikelets with an involucre, i. e. accompanied by bristles or enclosed 
in a spiny bur. 
Involucre of bristles. 5. Chetochloa. 
Involucre of valves forming a spiny bur. 6. Cenchrus. 
1. Panicum. 78. 
Plants annual. 
First empty scale not over %4 the length of the spikelet, truncate 
or triangular tipped. 1. P. dichotomiflorum. 
First empty scale at least ¥% the length of the spikelet, acute or 
acuminate. 
Panicle narrow, usually less than half as long as broad. 
2. P. flexile. 
Panicle as broad as long. 
Spikelets usually less than 2.5 mm. long. 3. P. capillare. 
Spikelets usually over 2.5 mm. long. 4. P. barbipulvinatum. 
Plants perennial. 
Basal leaves similar to those of the culm; not forming a winter 
rosette; first empty scale % as long as spikelet. 
5. P. virgatum. 
Basal leaves usually distinctly different from those of the culm, 
forming a winter rosette; first empty scale not more than % 
the length of the spikelet. 
Blades elongated, not over 5 mm. wide, 20 times as long as 
wide; autumnal form branching from base only. 
Spikelets usually over 3.2 mm. long, pointed. 
6. P. depauperatum. 
Spikelets usually less than 3.2 mm. long, blunt. 
Spikelets from 2.7 to 3.2 mm. long. 7. P. perlongum. 
Spikelets from 2.2 to 2.7 mm. long. 8. P. linearifolium. 
Blades not elongated, (or if so over 5 mm. wide and autumnal 
form not branched from the base). 
Spikelets neither turgid, blunt nor strongly nerved. 
Ligule of conspicuous hairs, usually 3-5 mm. long. 
Culms variously pubescent, if pilose the hairs not long 
and horizontally spreading. 
Autumnal form erect or leaning, never forming a mat. 
Blades stiff, erect. 9. P. huachuce. 
Blades lax, spreading. 9a. P. huachuce silvicola. 
Autumnal form branching from the middle nodes, form- 
ing widely spreading mats. (See also No. 9a.) 
10. P. tennesseense. 
