HITCHCOCK—MEXICAN GRASSES. 
Spikelets obtuse, 2mm. or more 
long. 
First glume nearly as long as 
the spikelet............ 42. P 
First glume about half as 
long as the spikelet ..... 4l. 
Culms not creeping at base. 
Plants forming conspicuous scaly 
rootstocks., 
Spikelets not over 2.4 mm. 
long; culms rarely over 30 
em. high...........------ 25. 
Spikelets 3.5 mm. or more long; 
culms 1 meter or more 
high. 
Spikelets 6 to 8 mm. long; 
culms decumbent at 
base. ....-.------------ 27. 
Spikelets 4 to 5 mm. long; 
culms erect..........--- 26. 
Plants not forming scaly root- 
stocks, 
Panicles 40 to 60 cm. long, the 
numerous elongated 
branches in verticils....... 43. 
Panicles not over 35 cm. long, 
usually much less, the 
branches not in verticils. 
Second glume and sterile 
lemma elongated, at least 
3 times as long as the 
fruit............ _ 17. 
Second glume and _ sterile 
lemma not elongated. 
Blades 2 cm. or more wide.. 21. 
Blades not over 1 cm. wide. 
Spikelets 4 to 4.2 mm. 
long, the midnerves 
of the glumes and 
sterile lemma sca- 
brous toward the 
APOX....-.--------- 19. 
Spikelets usually less 
than 3.5 mm. long. 
Blades hirsute on both 
surfaces (some- 
times glabrescent) 
not at all glau- 
COUS....-........- 20. 
Blades glabrous on 
both surfaces or 
with a few hairs on 
either surface, 
glaucous above... 18. 
. glutinosum. 
. millegrana. 
. gourm. 
. havardit. 
. virgatum. 
. megiston. 
. capillarioides. 
. hirsutum, 
. lepidulum. 
. ghiesbreghtii. 
. hall. 
245 
