66 POACEAE 



4. Amphilophis perforatus (Hack.) Nash. Stems tufted, 8-10 dm. tall, the nodes 

 barbed : leaf-sheaths and blades smooth and glabrous, or the latter with the upper sur- 

 face pubescent with long scattered hairs ; blades 2 dm. long or less, 2-4 mm. wide : panicle 

 6-8 cm. long, fan-shaped, much exserted : racemes 5-8^ 5-6 cm. long, the terminal hairs 

 about as long as the interned es : sessile spikelet 5-5.5 mm. long, the first scale with a 

 deep depression on the back above the middle, the fourth scale with a geniculate awn 2-2.5 

 cm. long, the column tightly spiral and much exserted ; pedicellate spikelet of a single 

 awnless scale about 3 mm. long. 



In dry soil, Texas and Mexico. Fall. 



11. SORGHUM Pers. 



Tall grasses, with usually broad flat leaf -blades and large terminal panicles, its primary 

 branches verticillate. Spikelets of 4 scales, in pairs, or in 3's at the end of the branches, 

 one sessile and perfect, the rest pedicellate and staminate, dorsally compressed, pubescent or 

 glabrous. Sessile spikelets with the outer 2 scales indurated, the third and fourth hya- 

 line, the latter awned or awnless. Pedicellate spikelets with the outer 2 scales firm -mem- 

 branous, or rarely reduced to 1 or 2 scales and sterile. Lodicules ciliate. Stamens 3. 

 Styles distinct. Stigmas plumose. 



1. Sorghum Halepfense (L. ) Pers. Smooth and glabrous. Stems 5-15 dm. tall, 

 from a long rootstock : leaf-blades 5 dm. long or less, 0.5-3 cm. wide : panicle 1.5-5 dm. 

 long, oblong to oval, its branches ascending, the longer ones 7-14 cm. long : sessile spike- 

 let 4.5-5.5 mm. long, ovate, the outer 2 scales densely appressed-pubescent with silky hairs 

 and indurated at maturity, the first scale 3-toothed at the apex, the readily deciduous awn 

 of the fourth scale 1-1.5 cm. long, geniculate, spiral below, the column much exserted ; 

 pedicellate spikelet 5-7 mm. long, lanceolate, the 2 outer scales sparingly pubescent. 



In fields and waste places, Pennsylvania to Kansas, Florida and Texas. Summer and fall- 

 JOHNSON-GRASS. 



12. SORGHASTRUM Nash. 



Usually tall perennial grasses, with flat leaf -blades and terminal panicles with the prim- 

 ary branches usually solitary and branched from the base, hence appearing as if whorled. 

 Sessile spikelets dorsally compressed, of 4 scales, the outer 2 indurated, often hairy, the 

 third and fourth scales hyaline, the latter long-awned, the awn spiral at the base. Pedi- 

 cellate spikelets wanting, or very rarely present as a minute rudiment, usually only the 

 hairy pedicels present, a single one at the side of each sessile spikelet, or 2, one on each 

 side, at the end of the branches. Lodicules glabrous. Stamens 3. . Styles distinct. 

 Stigmas plumose. 



Awn but once bent, 1-1.5 cm. long, the closely spiral portion but little exserted be- 

 yond the scales. 1. S. nutans. 

 Awn twice bent, 2-3 cm. long, the closely spiral portion extending to the second 



bend and much exserted beyond the scales. 



Branches of the panicle much exceeding the internodes of the axis, the ulti- 

 mate divisions of its branches straight. 2. S. Linnaeanum. 

 Branches of the one-sided panicle shorter than the internodes of the axis, the 

 ultimate divisions of the branches much curved, the spikelets hence re- 

 flexed. 3. S. secundum. 



1. Sorghastrum nutans (L. ) Nash. Stems 1-2.5 m. tall: leaf-sheaths usually 

 smooth and glabrous, or the lowermost ones sometimes pubescent ; blades 6 dm. long or 

 less, 13 mm. wide or less, very rough : panicle 2-5 dm. long, loose, the apex usually nod- 

 ding, its branches erect or nearly so, at least the lower ones much exceeding the internodes 

 of the axis, 7-10 cm. long, the ultimate divisions straight : spikelet 6-8 mm. long, lance- 

 olate, the 2 outer scales golden brown and indurated at maturity, the first one densely 

 pubescent with long erect hairs, the awn of the fourth scale geniculate, 1-1.5 cm. long, 

 closely spiral to the bend, thence loosely twisted, the column more or less exserted ; ped- 

 icel from 5 f as long as the spikelet. [Sorghum avenaceum (Michx. ) Chapm. ] 



In dry or moist soil, Ontario to Manitoba, Rhode Island, Florida, Texas and Arizona. Late sum- 

 mer and fall. INDIAN GRASS. 



2. Sorghastrum Linnaeanum (Hack.) Nash. Stems 1-1.5 m. tall: Jeaf -sheaths 

 smooth and glabrous ; blades 4 dm. long or less, 1 cm. wide or less, very rough : panicle 

 1.5-3 dm. long, the apex usually nodding, its branches erect or nearly so, at least the 

 lower ones much exceeding the internodes of the axis, 6-8 cm. long, the ultimate divisions 

 straight : spikelet 5.5-7.5 mm. long, lanceolate, the 2 outer scales blackish brown and in- 

 durated at maturity, the first one densely pubescent with long erect hairs, the awn of the 



