HITCHCOCK—MEXICAN GRASSES. 
Plants perennial. 
Plants producing creeping rhizomes, 
Inflorescence spike-like; blades firm, pungently in- 
volute-pointed..............000--- ee ee eee eee 21. 
Inflorescence a diffuse capillary panicle; blades flat, 
rather lax. 
Ligule 1 to 2 mm. long, auricled...............-.. 6. 
Ligule minute, not auricled.....................- 7. 
Plants tufted, not producing creeping rhizomes. 
Panicle large and open, the branches ascending, the 
lower 10 to 15 cm. long. 
Blades scabrous, elongated, the tip involute-attenu- 
ate; plants 1 to 2 meters high, in large tus- 
Blades smooth, glaucous, less than 10 cm. long; 
plants less than 1 meter high............... 9. 
Panicle narrower or more delicate. 
Panicle long and narrow, the branches appressed. 
Second glume shorter than the spikelet, little 
longer than the first; panicle densely 
flowered; spikelets about 2 mm. long... 
Second glume about as long as the spikelet. 
Panicle narrow but not strict and spike- 
like; blades, at least the lower, cili- 
ate; sheaths glabrous or sparsely 
pilose at the throat................ 
Panicle elongated, strict and spike-like; 
blades not ciliate or only slightly so 
at base; sheaths strongly pilose at 
throat... cece eee eee e eee 
Panicle pyramidal or oblong, the main branches 
spreading or ascending (only of the exserted 
portion in S. cryptandrus). 
Panicle even at maturity inclosed at base in 
the uppermost sheath; leaves strongly 
bearded at the throat. 
Branches of panicle flexuous, slender. ...- 
Branches of panicle not flexuous.......... 
Panicle exserted at maturity. 
Branches of panicle elongated, naked be- 
low; blades flat, lax, as much as 1 
cm, wide; sheaths ciliate, densely 
short-pilose on the collar........... 
Branches of panicle not conspicuously 
elongated. 
Spikelets all on slender pedicels; 
glumes unequal, both shorter 
than the spikelet.............- 
Spikelets short-pediceled, more or less 
secund along the main branches. 
“owermost panicle branches sev- 
eral in a whorl. 
Spikelets 1.5 mm. long....... 
Spikelets 3 mm. long........ 
19 
see . 10. 
13. 
14. 
307 
S. virginicus. 
S. auriculatus. 
S. asperifolius. 
_ S. wrightii. 
S. palmeri. 
. S. indicus. 
. S. purpurascens. 
S. strictus. 
.S. fleruosus. 
. S. cryptandrus. 
S. buckleyi. 
S. trichodes. 
. S. argutus. 
. &, erectus. 
