GENERA OF GRASSES OF THE UNITED STATES. 269° 
has narrower blades than plants of sorghum of the same height. 
The characteriscic difference is the presence of the creeping rhizomes 
in the former. Johnson grass is a native of the Mediterranean 
region, but is now widely distributed in the warmer parts of 
America. In the United States it is common throughout the 
South, where it is often a troublesome weed. It is an ex- 
cellent and much-used forage grass, but. the difficulty of eradicating 
it from ground that it has once occupied offsets its forage value. 
Johnson grass has become an especially pernicious weed on the 
Black Lands of Alabama and Texas.' 
The sorghums and Johnson grass sometimes produce hydrocyanic 
acid in sufficient abundance, especially in second growth, to poison 
grazing animals. : 
134. SoreHastrum Nash. 
Spikelets in pairs, one nearly terete, sessile, and fertile, the other 
wanting, only the hairy pedicel being present; glumes coriaceous, 
brown or yellowish, the first hirsute, the edges inflexed over the 
second; sterile and fertile lemmas thin and hyaline, the latter ex- 
tending into a usually well-developed bent and twisted awn. 
Perennial, erect, rather tall grasses, with narrow flat blades and 
narrow terminal panicles of one to few jointed racemes. Species 
about 10 in the warmer parts of the Western Hemisphere, and a 
few in Africa; 3 species in the United States east of the Rocky 
Mountains. 
Type species: Andropogon avenaceus Michx. 
Poranthera Raf., Bull. Bot. Seringe 1: 221, 1830, not Rudge, 1811. “Andro- 
pogon nutans [L.] et ciliatus [Ell.])” are cited. These names apply to the 
same species, Sorghastrum nutans (L.) Nash. 
Sorghastrum Nash, in Britton, Man, 71. 1901. Only one species described. 
S. avenaceum (Michx.) Nash. 
Chalcoelytrum Lunell, Amer. Mid], Nat. 4: 212. 1915. The name proposed to 
replace Sorghastrum Nash, which, being built on Sorghum, is considered unde- 
sirable. 
The units of the inflorescence are racemes reduced‘to one or two 
joints, or in Sorghastrwm nutans sometimes four or five. The slen- 
der, villous rachis disarticulates at the top of each joint, the spikelets 
falling with two villous stalks attached, one the rachis joint, the 
other the pedicel of the obsolete sterile spikelet. The articulation is 
more or less oblique, leaving a bearded blunt callus or, in some South 
American species, a long, sharp callus. In S. nutans the racemes not 
infrequently occur in pairs with a sessile spikelet in the fork, that 
is, the pedicel of the sterile spikelet of the lowest joint has been re- 
placed by a short raceme of one or two joints. 
1For methods of eradication, see Cates and Spillman, U. §. Dept. Agr., Farmers’ Bull, 
279. 1907. 
