GENERA OF GRASSES OF THE UNITED STATES. 
273 
much shorter than the very thin sterile and fertile lemmas. The 
awn is about 6 inches long, twisted and bent. The species before 
maturity furnishes forage on the grassy pinelands of southern 
Florida. 
136. Heteropogon Pers. 
Spikelets in pairs, one sessile, the other pedicellate, both of the 
lower few to several pairs staminate or neuter, the remainder of the 
sessile spikelets perfect, terete, long-awned, the pedicellate spikelets, 
like the lower, staminate, flat, conspicuous, awnless; glumes of the 
fertile spikelet equal, coriaceous, the first brown-hirsute, infolding 
the second; lemmas thin and hyaline, the fertile one narrow, extend- 
ing into a strong bent and twisted brown awn ; palea wanting ; glumes 
of the staminate spikelet membranaceous, the first green, faintly many 
nerved, asymmetric, one submarginal keel rather broadly winged, 
the other wingless, the margins inflexed, the second glume narrower, 
symmetric; lemmas hyaline; palea wanting. 
Annual or perennial, often robust grasses, with flat blades and soli- 
tary racemes terminal on the culms and branches ; rachis slender, the 
lower part, bearing the pairs of staminate spikelets, continuous, the 
remainder disarticulating obliquely at the base of each joint, the joint 
forming a sharp barbed callus below the fertile spikelet, the pedicel- 
late spikelet readily falling, its pedicel remaining, obscured in the 
hairs of the callus. Species about seven, in the warmer regions of 
both hemispheres ; two in the United States, from Florida to Arizona. 
Type species : Heteropogon glaber Pers. 
Heteropogon Pers., Syn. PI. 2 : 533. 1807. Persoon describes two species, H. 
glaber, of which he gives as synonyms Andropogon allioni DC. and A. con- 
tortus All., and R. hirtus, of which he gives as a synonym Andropogon con- 
tortus L. The first is selected as the type. 
Spirotheros Raf., Bull. Bot. Seringe 1 : 221. 1830. A single species, " Stipa 
melanocarpa Muhl., Andropogon melanocarpus Ell.," is given. 
The two species in the United States are Heteropogon contortus 
(L.) Beauv. (fig. 16'5), a perennial, 1 to 3 feet tall, the first glume 
of the staminate spikelets papillose-pilose, sometimes sparsely so, 
and H. melanocarpus (Ell.) Benth., an annual, 4 to 7 feet tall and 
often much branched, the first glume of the staminate spikelets bear- 
ing a row of glands along the back. The first species is found in 
rocky places from Texas to Arizona. The second is found in Florida, 
Georgia, and Alabama ; also in Arizona. The oil glands on the in- 
florescence of the latter give the plant an oclor like that of citronella 
oil. 
Heteropogon contortus is an important forage grass but does not 
extend far into the United States. In the Hawaiian Islands, where 
it is called pili, it is an important range grass on the drier areas. It 
was used by the natives to thatch their grass huts. The mature fruits 
are injurious to sheep. 
97769°— 19— Bull. 772 18 
