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 internodes: sessile spikelet 5-5.5 mm. long, the first scale with a 

 deep depression on the back above the middle, the fourth scale with ageniculate 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. SORGHASTRTJM 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 - i | 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: leaf -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 



