278 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM, 
Sterile or pedicellate spikelets much smaller than the fertile ones, often rudi- 
mentary (about as large in A. pertusus and A. annulatus with several 
racemes). 
Racemes solitary at the ends of the culms or branches, from bractlike 
sheaths; rachis joints clavate, the apex with a cuplike hollow, 
(Subgenus ScHIzZACHYRIUM. ) 
Plants annual. 
Culms weak, decumbent ; blades obtuse, 2 to 4 em. long; peduncles 
capillary, spreading _-----~----- 2. A. brevifolius. 
Culms erect ; blades acute, usually 5 to 10 em. long; peduncles slen- 
der, but not capillary_______________ 3. A. malacostachyus, 
Plants perennial. 
Rachis conspicuously flexuous, very slender, the spikelets spreading, 
Blades flat; racemes very numerous in a corymbose panicle ; 
plants robust _.-...-....-_________ 4, A. condensatus. 
Blades involute; racemes few; plants slender. 
Racemes densely white-villous with long hairs; blades firm, 
6. A. gracilis, 
Racemes sparsely villous; blades rather soft. 
7. A. cubensis. 
Rachis straight, the spikelets appressed or narrowly ascending. 
Spikelets awnless. 
Racemes 1 to 2 cm. long, partly inclosed in the subtending 
spathe, numerous, aggregated in a narrow panicle. 
8. A. virgatus. 
Racemes 4 to 8 cm. long, few, exserted__9. A. salzmanni. 
Spikelets awned. 
First glume of the sessile spikelet villous. 
12. A. hirtiflorus. 
First glume of the sessile spikelet glabrous or nearly so. 
Blades terete-filiform; sessile spikelet 1.5 mm. broad. 
5. A. multinervosus. 
Blades flat or folded or sometimes involute toward the 
apex. 
Sessile spikelet about 4 mm. long, 1 mm, wide; 
blades not over 1.5 mm. wide. 
13. A. tener. 
Sessile spikelet about 5 mm. long; blades 2 to 5 
mm, wide _____________ 14, A. semiberbis. 
Racemes 2 or more together at the ends of the culms or branches. 
Plants annual; racemes several on capillary flexuous peduncles. 
15. A. piptatherus. 
Plants perennial; peduncles not capillary nor flexuous. 
Racemes numerous or several arranged along an axis, forming a 
panicle. 
Pedicellate spikelet much smaller than the fertile one, the 
latter not pitted _18. A. saccharoides. 
Pedicellate spikelet about as large as the fertile one. 
First glume with a pinhole-like pit on the back. 
16. A. pertusus. 
First glume not pitted_______-________ 17. A. annulatus. 
Racemes 2 to 4 (sometimes more in A. selloanus), fascicled, sub- 
tended by a bladeless sheath (spathe), exserted or partly in- 
cluded in it. 
