MANUAL OF THE GRASSES OF THE UNITED STATES 575 



la. Rachis winged or flat-margined, the margin as wide as the central rib; plants annual, 

 creeping at least at base. 

 Rachis bearing scattered long fine hairs (these rarely wanting) ; spikelets narrow, acumi- 

 nate, nearly glabrous 2. D. horizontals. 



Rachis not bearing hairs; spikelets elliptic, acute, pubescent. 



Plants perennial, stoloniferous 7. D. longiflora. 



Plants annual. Culms erect or decumbent spreading. 

 Sheaths glabrous; fertile lemma brown. 



Spikelets 2 mm. long, 1 mm. wide, the hairs or most of them capitellate. 



3. D. ISCHAEMUM. 

 Spikelets 1.5 to 1.7 mm. long, about 0.6 mm. wide, the hairs not capitellate. 

 Sterile lemma with 5 distinct nerves; spikelets sparingly pubescent, 1.7 mm. long; 

 fertile lemma light brown; racemes, if more than 2, not digitate. 



4. D. FLORIDANA. 



Sterile lemma with 3 distinct nerves; spikelets distinctly pubescent, 1 .5 mm. long, 

 fertile lemma dark brown, racemes usually all digitate. 



5. D. VIOLASCENS. 



Sheaths pilose or villous; fertile lemma pale. 



Spikelets 1.5 to 1.7 mm. long; pedicels terete, glabrous 6. D. serotina. 



Spikelets 2.5 to 3.5 mm. long; pedicels angled, scabrous 1. D. sanguinalis. 



lb. Rachis wingless or with a very narrow margin (see also D. horizontalis), triangular; 

 plants not creeping (except in D. texana), annual or perennial. 

 2a. Fertile lemma pale or gray. 



Plants annual, decumbent and rooting at base. Spikelets 3 mm. long, glabrous or nearly 



so 8. D. SIMPSONI. 



Plants perennial. 



Spikelets densely or sparsely villous; racemes 5 to 10. 



Spikelets 2.8 to 3.5 mm. long, sparsely to densely villous 14. D. runyoni. 



Spikelets 2 to 2.5 mm. long, rather sparsely villous 13. D. texana. 



Spikelets glabrous to obscurely appressed-pubescent on the internerves: racemes 2 to 

 5, some of them naked at base for 1 to 1.5 cm. 

 First glume broad, hyaline, minute but obvious; spikelets 3.2 mm. long, glabrous. 



15. D. PAUCIFLORA. 



First glume obsolete or nearly so; spikelets 2.5 to 2.8 mm. long, obscurely to obvi- 

 ously appressed-pubescent. 

 Racemes 2 to 4; culms ascending from a curved base; sheaths papillose-pilose. 



16. D. SUBCALVA. 



Racemes 5 to 10; culms erect; sheaths conspicuously villous. 



17. D. ALBICOMA. 



2b. Fertile lemma dark brown. Plants erect or at least not rooting at the decumbent base; 

 annual or sometimes apparently perennial. 

 Second glume and sterile lemma glabrous (see also D. laeviglumis under D. filiformis). 



12. D. GRACILLIMA. 



Second glume and sterile lemma capitellate-pubescent. 



Spikelets 2 to 2.5 mm. long 10. D. villosa. 



Spikelets 1.5 to 1.7 mm. long. 



Blades folded or involute, flexuous 11. D. dolichophylla. 



Blades flat 9. D. filiformis. 



1. Digitaria sanguinalis (L.) Scop. 

 Crabgrass. (Fig. 827.) Plant branch- row, ciliate; sterile lemma strongly 

 ing and spreading, often purplish, nerved, the lateral internerves ap- 

 rooting at the decumbent base, the pressed-pubescent, the hairs some- 

 culms sometimes as much as 1 m. times spreading at maturity (D. fim- 

 long, the flowering shoots ascending ; briata Link) ; fertile lemma pale. 

 sheaths, at least the lower, papillose- — Fields, gardens, and waste places, 

 pilose ; blades 5 to 10 mm. wide, pu- a troublesome weed in lawns and cul- 

 bescent to scaberulous ; racemes few tivated ground throughout the United 

 to several, 5 to 15 cm. long, rarely States at low and medium altitudes, 

 longer, digitate, with usually 1 or 2 more common in the East and South ; 

 whorls a short distance below; spike- temperate and tropical regions of the 

 lets about 3 mm. long; first glume world. Native of Europe. A specimen 

 minute but evident; second glume with nearly glabrous sheaths and in- 

 about half as long as the spikelet, nar- florescences of 2 racemes collected by 



