MANUAL OF THE GRASSES OF THE UNITED STATES 



557 



3. Digitaria ischaemum (Schreb.) Muhl. Smooth crabgrass. 

 (Fig. 1162.) Erect or usually soon decumbent-spreading, resembling 

 D. sanguinalis but not so coarse or tall; foliage glabrous, more purple; 

 racemes mostly 2 to 6, 4 to 10 cm long, the rachis with thin wings 

 wider than the midrib; spikelets about 2 mm long; first glume hyaline, 

 obscure; second glume and sterile lemma as long as the dark fertile 

 lemma, pubescent with capitellate hairs, o (Syntherisma humi- 

 jusum Rydb.) — Waste places, often a troublesome weed in lawns, 

 Quebec to North Dakota, south to South Carolina, Tennessee, and 

 Arkansas, occasionally farther west (fig. 1163) ; introduced from Eurasia. 

 The first glume is so thin as to be apparently wanting. Digitaria 

 ischaemum var. mississippiensis (Gattinger) Fernald. Taller, the 

 racemes mostly 5 to 7, often 10 or even 15 cm long; first glume often 

 more easily seen, o — Maryland, Tennessee, and South Carolina. 



Figure 1161. — Digitaria horizontalis. Plant, X 1; 

 spikelet and floret, X 10. (Nash 996, Fla.) 



Figure 1162. — Digitaria inchaemum. Plant, X 1 ; 

 spikelet and floret, X 10. (Jones 1761, Vt.) 



4. Digitaria Iloridana Hitchc. (Fig. 1164.) Culms tufted, decum- 

 bent at base, 20 to 30 cm tall; foliage glabrous except for a few long 

 hairs around the mouth of the sheath ; blades 4 to 7 cm long, 3 to 6 nun 

 wide; racemes 3 or 4, rather distant on the axis, 3 to 6 cm long, the 

 rachis wings wider than the midrib; spikelets 1.5 to 1.7 mm long, 

 rather sparingly pubescent; first glume wanting; second glume and 

 sterile lemma about as long as the light brown fertile lemma. o — 

 Known only from sandy pine woods, Hernando County, Fla. The 

 inflorescence resembles that of D.jiliformis, but the rachis is winged; 

 the spikelets are smaller than those of D. ischaemum. 



5. Digitaria violascens Link. (Fig. 1165, B.) Annual or ap- 

 parently perennial; culms numerous in a tuft, spreading at base, 

 slender, 10 to 40 cm tall; leaves mostly clustered near the base, the 

 sheaths glabrous; blades flat, mostly less than 5 cm long, 3 to 6 mm 



