No. 18. 
SPOROBOLUS INTERRUPTUS Vasey. (Vilfa interrupta Vasey in 
Special Report No. 63, Department of Agriculture, 1883.) 
Plant perennial, with densely tufted, bulbous base. 
Culms erect, not branching, smooth, terete, 1 to 2 feet tall. 
Leaves; radical and from radical shoots, numerous, with scarious, often red- 
dish, glabrous or pubescent, tapering sheaths, and mostly flat, smooth or loosely 
pubescent erect blades, 3 to 5 inches long; of culm 2 or 3 ; sheaths longer than in- 
ternodes, close, open above, smooth blades, mostly involute, erect, 1 line wide, 1 
to 3 inches long; ligule a narrow ciliate fringe. 
_ Inflorescence a narrow, open or interrupted, erect panicle, 4 to 6 inches long; 
rachis flexuous, branches alternate or verticillate below, in twos or threes above, 
1 to 2 inches long. 
Spikelets short-pedicellate, narrow, 1- or 2-flowered, 2 to 3 lines long; first 
glume lanceolate, acute, carinate, scarious, smooth, 1-nerved, 1 to 1} lines long; 
second glume ovate-lanceolate, nearly twice as large; floral glume ovate-lanceo- 
late, acute, membranaceous, smooth, I-nerved or obscurely 3-nerved above, 2 to 3 
lines long; palet broadly lanceolate, bifid at apex, thin. hyaline, smooth, slightly 
2-keeled, 2 lines long; anthers 3, long, reddish purple; stigmas 2, greenish, 
plumose. 
Grain, no mature grains seen. 
PLaTe XVIII; a, s 
palet; 2, typical panicle. 
Arizona, 
pikelet enlarged; b, empty glumes; c, floral glume; d, 
