44 
KEY TO THE GENERA. 
Tribe I. MAYDEAE. 
A single genus.........2..2-2- 20 2c eee cece ee eee eee 
1. 
CONTRIBUTIONS FROM THE NATIONAL HERBARIUM, 
TRIPSACUM (p. 49). 
Tribe 1, ANDROPOGONEAE. 
Spikelets all pedicellate, the longer pediceled one per- 
fect, long-awned, the short-pediceled one stami- 
nate, awnless.............-02.-0ceeeeeeeeeeeee 
Some of the spikelets sessile, these perfect, the pedi- 
cellate spikelets staminate, sterile, or reduced 
to a pedicel. 
Spikelets all awnless...............2.2....200-- 3. 
Perfect spikelets awned. 
Lower spikelets unlike the others............ 9. 
Sessile spikelets all alike. 
Racemes single; rachis joints with a cup- 
shaped appendage at the tip...... 4, 
Racemes 2 or more; rachis joints not ap- 
pendaged. 
Rachis joints and pedicels sulcate, 
translucent................-. 5. 
Rachis neither sulcate nor trans- 
lucent, 
Some of the racemes sessile... .. 6. 
All the racemes pedunculate. 
Pedicellate spikelets re- 
duced to a pedicel... 8. 
Pedicellate spikelets stami- 
Tribe I. ZOYSIEAE. 
Second glumes covered with hooked spines.......... 10. 
. Hmaria (p. 53). 
Second glumes not spiny............-...-2---2-2----- 
Tribe IV. PANICEAE. 
Spikelets involucrate. 
Involucre a spiny bur, falling with the spikelets. .20. 
Involucre of numerous bristles, persistent on the 
axis after the fall of the spikelets.......... 19. 
Spikelets not involucrate. 
Glumezs, at least the second, awned or cuspidate. .18. 
Glumes not awned. 
Spikelets lanceolate; fruit cartilaginous, not 
rigid, the white hyaline margins of the 
lemma not inrolled. 
Spikelets densely covered with long 
silky hairs....................--- 12, 
Spikelets glabrous or nearly so. 
Inflorescence of slender racemes, 
digitately arranged........... 13. 
Inflorescence a capillary panicle... .14. 
2. 
TRACHYPOGON (p. 49). 
ELYONURUS (p. 49). 
HETEROPOGON (p. 52). 
ScHIZACHYRIUM (p. 49). 
AMPHILOPHIS (p. 50). 
ANDROPOGON (p. 51). 
SorGHastroum (p. 52), 
. Hocus (p. 51). 
Nazi (p. 52). 
CENCHRUS (D. 61), 
CHAETOCHLOA (p. 60). 
EcuHINoca1oa (p. 59). 
Vaxota (p. 54). 
SYNTHERISMA (p. 54), 
LEPTOLOMA (p. 54). 
