270 BULLETIN 772, U. S. DEPARTMENT OF AGRICULTURE. 
The commonest species of the genus in the United States is Sor- _ 
ghastrum nutans (L.) Nash (fig. 163), sometimes called Indian reed 
or Indian grass. This is a tall, erect grass with handsome bronze- 
colored panicles as much as a foot long, the awns about half an inch 
long, the anthers brilliant yellow. The species is found in prairies 
and open woods throughout the eastern United States and south- 
westward to Arizona and Mexico. It is a common constituent of 
prairie hay in the eastern part of the Great Plains region. 
Two other species are found in the Southern States, both with 
awns about an inch long, Sorghastrum elliottit (C. Mohr) Nash, with 
pedicels villous only at the very tip, and S. secundum (Chapm.) Nash, 
with a one-sided panicle and pedicels villous along the upper portion. 
185. RHAapPHIS Lour. 
Spikelets in threes, one sessile and perfect, the other two pedicellate 
and sterile, or sometimes a pair below, one fertile and one sterile; 
fertile spikelet terete, the glumes coriaceous; sterile and fertile 
lemmas thin and hyaline, the latter long-awned. 
Perennial grasses, or our species annual, with open panicles, the 
three spikelets (reduced racemes) borne at the ends of long, slender, 
naked branches. Species about 20, all in the tropical regions of the 
Eastern Hemisphere except the 1 found in the southern United States. 
Type species: Rhaphis trivialis Lour. 
Rhaphis Lour., Fl. Cochinch. 558. 1790. Only one species described, which 
is the same as Andropogon aciculatus Retz. Some authors have thought the 
name Rhaphis was invalidated by the earlier Rhapis L. f. (1789), a genus of 
palms. The names have a different derivation and a different pronunciation, 
and the one does not invalidate the other. 
Pollinia Spreng., Pugill. 2: 10, 1815, not Pollinia Trin., 1832. Type species, 
P, gryllus Spreng. (Andropogon gryllus L.). Several species are described, 
but the generic characters are given under the first species. 
Centrophorum Trin., Fund. Agrost. 106, pl. 5. 1820. Type species, C. chinense 
Trin. (Andropogon aciculatus Retz.), the only one described. 
Chrysopogon Trin., Fund. Agrost. 187. 1820. Type species, Andropogon 
gryllus L. Two species are mentioned, C. gryllus and C. aciculatus, but an 
illustration of the first is cited. 
The only species occurring in the United States is Rhaphis pauci- 
flora (Chapm.) Nash (fig. 164), an annual found in Florida and 
Cuba. This has the aspect of a species of Stipa, the spikelets with 
their long awns and barbed callus resembling the fruit of Stipa 
spartea. ‘The long slender branches of the few-flowered panicle bear 
a terete, brown, sessile fertile spikelet and two slender sterile pedicels, 
each with a slender glume. The peduncle disarticulates by a long 
oblique line through the thickened villous end, the portion separating 
with the spikelet being densely brown-villous, this forming a long 
sharp callus. The glumes are coriaceous and at maturity separate 
somewhat, the spikelet gaping at the apex. The palea is present, but 
