146 POACEAK 



dry, the uppermost one much exceeding the inflorescence : inflorescence included at the 

 base, the exserted portion 12 cm. long or less, its branches erect, the larger 5-7 cm. long : 

 spikelets about 1 cm. long ; scales 8-10, the lower empty ones acuminate, usually awned or 

 awn-pointed, the flowering scales, exclusive of the awn, 4.5-5 mm. long, acuminate at the 

 2-toothed apex, the nerves pilose below the middle, the lateral ones usually slightly excur- 

 rent, the awn as long as the scale-body or more. [Leptochloa polystachya Chapm.] 

 In brackish marshes, New York to South Carolina. Summer and fall. 



5. Diplachne Halei Nash. Stems 6-10 dm. tall, finally branched: leaf-sheaths 

 smooth ; blades erect or ascending, 1.5-4 dm. long, 6-12 mm. wide, flat, very rough : in- 

 florescence finally exserted, 2-3 dm. long, 4-10 cm. wide, its numerous branches ascending, 

 4-7 cm. long : spikelets 4-6 mm. long, about 2 mm. wide ; scales 7-10, the lower empty 

 ones rough, the first scale acute, the second obtuse, the flowering scales about 3 mm. long, 

 slightly and usually obtusely 2-toothed at the obtuse apex, the lateral nerves pilose toward 

 the base, not excurrent, the midnerve glabrous or pilose toward the base, excurrent in an 

 awn 0.2 mm. long or less. 



In marshes, Louisiana to Texas. Summer and fall. 



6. Diplachne dubla (H.B.K.) Benth. Stems tufted, 3-10 dm. tall, simple: leaf- 

 sheaths smooth ; blades erect, smooth or rough, 2-8 mm. wide, the uppermost one 1.5-8 

 cm. long, the lower 1.5-4 dm. long : inflorescence usually finally exserted, 1-2 dm. long, 

 the 5-20 racemes erect to spreading, the larger 5-11 cm. long : spikelets 5-9 mm. long ; 

 scales 5-10, the lower empty ones acuminate, the flowering scales about 4.5 mm. long, ob- 

 long, rough at the 2-lobed apex, the lobes rounded at the summit, the nerves glabrous, the 

 lateral ones vanishing considerably below the apex of the lobes, the midnerve at the cleft 

 or rarely extending into a short awn, the margins of the scale pilose below the middle. 



In woods anil rocky places, Florida to Texas, Arizona and Mexico. Summer and fall. 



102. RHOMBOLYTRUM Link. 



Perennial grasses, with usually flat leaf-blades and a narrow contracted spike-like 

 panicle. Spikelets numerous, several-flowered. Scales several ; 2 lower empty, 1 -nerved ; 

 flowering scales broad, rounded at the summit, 3-nerved, the nerves glabrous, the lateral 

 ones disappearing below the margin, the midnerve at the margin or sometimes excurren 

 as a short projection. Stamens 3. Styles short, distinct. Stigmas plumose. 



1. Rhombolytrum albescens (Munro) Nash. Stems 2-6 dm. tall : leaf-sheaths 

 shorter than the internodes ; blades ascending, 0.5-2 dm. long, 2-5 mm. wide, smooth : 

 panicle contracted, spike-like, 6-15 cm. long, 8-15 mm. broad, its branches short and 

 appressed : spikelets 4.5-5 mm. long, about 2.5 mm. wide, oval ; scales 8-10, the 2 outer 

 empty ones rather broad, 1-nerved, the flowering scales about 3 mm. long, nearly orbicular 

 when spread out, rounded at the erose and sometimes acuminately 2-toothed apex, 3- 

 nerved, the nerves glabrous, the lateral ones vanishing below the margin, the midnerve at 

 the margin or sometimes excurrent as a short projection . 



In dry gravelly soil, Texas to Arixona. Summer. 



103. ERAGROSTIS Beauv. 



Low or tall annual or perennial tufted rarely dioecious grasses, the stems sometimes 

 prostrate or creeping, with flat or convolute leaf-blades and open or contracted panicles. 

 Spikelets numerous, arranged singly or in fascicles, 2 -many-flowered, the flowers perfect or 

 unisexual. Scales 4- many, membranous, compressed, keeled, the 2 lower empty, unequal, 

 the remaining scales larger, 3-nerved, obtuse or acute at the apex ; palet shorter than the 

 scale, prominently 2-nerved or 2-keeled, often incurved and persistent on the rachilla after 

 the fall of the scale. Stamens 2 or 3. Styles distinct, short. Stigmas plumose. 



A. Stems not creeping : flowers perfect. 



a. Palet of the spikelets glabrous on the keels or merely hispidulous. 

 * Annuals. 



Spikelets 2-5-flowered. 



Pedicels and branches of the panicle short : stems usually branched 



above. 1. E. Frankii. 



Pedicels and branches of the diffuse panicle long and capillary : stems 



branched only at the base. 

 Stems slender, rarely equalling 5dm. in height : leaf-blades usually 



1.5 dm. long or less. 2. E. capillaris. 



Stems stout, 8-12 dm. tall : leaf-blades elongated, 4-6 dm. long. 3. E. fiirsuta. 



Spikelets more than 5-flowered. 



Panicle narrow, elongated, 2.5-5 dm . long, its branches erect or nearly 



so: spikelets crowded. 4. E. glomcrata. 



