14 POACEAE. 



racemes 2-5 cm. long, nearly 1 cm. in diameter, exclusive of the bristles, the 

 rachis pubescent: bristles 5-10 mm. long: spikelets ovoid, acute, 2-2.5 mm. 

 long, the flowering scale acute, striate, finely transverse-rugose. — Low ham- 

 mocks, L. keys. — [E. K.] — {Ber., Bah., Cuba, Ant.) 



^.. 2. C. gracilis (H.B.K.) Scribn. & Merr. Stems erect, 3-7 dm. tall, slender: 

 blades involute-setaceous, 2 dm. long or less, 1-3 mm. w-ide: racemes 2-6 cm. 

 long, 3-5 mm. in diameter: bristles 5-8, very short, equalling or twice as long 

 as the spikelet: spikelets 2 mm. long, ovoid, acute, the flowering scale acute, 

 abruptly apiculate, transversely rugose. — Hammocks and cultivated grounds, 

 L. keys. 



3. C. magna (Griseb.) Scribn. Stems stout, 1-4 m. tall, branching at the 

 base: leaf -sheaths glabrous, compressed; blades 3-6 dm. long, 1-3 cm. wide, 

 rough: panicle usually interrupted below, 1-3.5 dm. long, 2-5 cm. in diameter; 

 bristles 1-3, green, 8-11 mm. long: spikelets elliptic, acute, 2 mm. long. — 

 Hammocks and sand-dunes, U. keys. — [E. K.] — (^Ant.') 



- '-• 4. C. macrosperma Scribn. & Merr. Stems 6-12 dm. tall : leaf -blades linear- 

 lanceolate, 1-3 dm. long: panicle 1-2.5 dm. long, 2-4 cm. in diameter, exclusive 

 of the bristles: bristles single, 1.5-3 cm. long, green: spikelets narrowly ovoid, 

 acute, 3 mm. long, the flowering scale acute, narrowly ovoid, finely transverse- 

 rugose. — Hammocks and sand-dunes, U. keys. — [E, K.] — (Bah.) 



j.t; 5. C, caudata (Lam.) Scribn. Stems 3-6 dm. tall: leaf-sheaths pubescent: 

 blades linear, 1-3 dm. long, 3-5 mm. wide, pubescent, filiform-attenuate at the 

 apex: panicle 5-15 cm. long, the rachis slender and flexuous, pilose: bristles 

 single, flexuous, 4-10 mm. long : spikelets ovoid, acute, the flowering scale ovoid, 

 acute, short-apiculate, transversely undulate-rugose below. — Low hammocks and 

 cultivated grounds. Key West. — {Cuba, Ant.) 



yi 14. CENCHE.OPSIS Nash. Erect plants with long rootstocks and terminal 

 spicate inflorescence. Spikelets single, the involucre of 1 or 2 outer rows of 

 barbed bristles and 1 or 2 inner rows of barbed spines which are 2-4 times as 

 long as the bristles and about equalling the spikelet. Scales 4. 



1. C. myosuroides (H.B.K.) Nash. Stems 6-14 dm. tall: leaf -blades 1-3 dm. 

 long, 3-8 mm. wide: spikes 5-20 cm. long: involucres numerous: spikelets 

 about 5 mm. long. — Pinelands and edges of hammocks, U. keys, L. keys. — 

 [E. 'K.]—{Ba'h., Cuba, Ant.) 



' 15. CENCHKUS L. Diffuse plants with terminal spikes. Spikelets 2-6, 

 in an involucre of two thick hard valves. Scales 4, awnless. — Sand-bue. 

 Sand-spur. Bur-grass. Cockspur. 



Involucre awned at the base. 



Involucre with short, generally reflexed, spines at the glabrous base: spikelets 2 

 in an involucre. 1. G. carolinianus. 



Involucre with erect barbed bristles at the villous base : spike- 

 lets 3 or 4 in an involucre. 

 Spikelets 4 in an involucre : spines on the involucre not 



basal. 2. C. echinatus. 



Spikelets 3 in an involucre : spines on the involucre basal. 3. C. viridis. 

 Involucre naked at the base. 4. C. incertus. 



1. C. carolinianus L. Stems 2-6 dm. long, branching: leaf -blades 6-12 cm. 

 long, 4-8 mm. wide: spikes 3-6 cm. long: involucres 6-20, the spines 3— i mm. 

 long: spikelets 6-7 mm. long, usually not exserted beyond the involucre. — 

 Hammocks and pinelands, U. keys, L. keys, L. S. keys. — [E. K.] — (Bah., Cuba, 

 Ant.) 

 S'C2. C. echinatus L. Stems branched: blades 1^ dm. long, 5-15 mm. vdde: 

 spikes 4-12 em. long: involucres 20-50, densely crowded, green to purplish, 

 villous at the base, the spines 3-4 mm. long: spikelets 6-7 mm. long, exserted 



