576 



MISC. PUBLICATION 200, U. S. DEPT. OF AGRICULTURE 



(Fig. 829.) Erect or usually soon 

 decumbent-spreading, resembling D. 

 sanguinalis but not so coarse or tall; 

 foliage glabrous, bluish or purplish; 

 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, ob- 

 scure; second glume and sterile lem- 

 ma as long as the dark fertile lemma, 

 pubescent with capitellate hairs. O 

 (Syntherisma humifusum Rydb.) — 

 Waste places, often a troublesome 

 weed in lawns. Quebec to Georgia, 

 west to Washington and California; 

 introduced from Eurasia. The first 

 glume is so thin as to be apparently 

 wanting. Digitaeia ischaemtjm 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, Indiana, Illinois, Vir- 

 ginia, Tennessee, South Carolina, 

 and Georgia. 



4. Digitaria floridana Hitchc. (Fig. 

 830.) Culms tufted, decumbent at 

 base, 20 to 30 cm. tall; foliage gla- 

 brous except for a few long hairs 

 around the mouth of the sheath; 

 blades 4 to 7 cm. long, 3 to 6 mm. 

 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 want- 

 ing; second glume and sterile lemma 

 about as long as the light-brown 

 fertile lemma. — Sandy pine 

 woods, Florida (Hernando County). 

 The inflorescence resembles that of 

 D. filiformis, but the rachis is winged; 

 the spikelets are smaller than those 

 of D. ischaemum. 



5. Digitaria violascens Link. (Fig. 

 831.) Annual or apparently 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. wide, the upper culm blade 

 distant, reduced; racemes slender, 2 

 to 5, usually 2 or 3, digitate or some- 



Figure 826. — Trichachne hitchcockii. Plant, X 1 ; 

 spikelet and floret, X 10. (Type.) 



Tracy in Mississippi, said to be in- 

 troduced, has been erroneously re- 

 ferred to Syntherisma barbatum 

 (Willd.) Nash (Digitaria barbata 

 Willd.). 



Digitaria sanguinalis var. cili- 

 aris (Retz.) Pari. Sterile lemma, 

 pectinate-ciliate, the stiff cilia 1.5 

 mm. long. Along railroad, Berks 

 County, Pa. Waif from Asia. 



2. Digitaria horizontals Willd. 

 (Fig. 828.) Resembling D. sanguina- 

 lis, the culms more slender, the 

 racemes mostly subracemose, very 

 slender, lax, the rachis scarcely winged, 

 bearing scattered long fine spreading 

 hairs (these rarely wanting); spike- 

 lets narrow, about 2 mm. long; first 

 glume minute or obsolete; second 

 glume half as long as the spikelet. 

 O (Syntherisma setosum Nash; S. 

 digitatum Hitchc.) — Waste places, 

 southern and central Florida; ballast, 

 Mobile, Ala.; tropical regions of 

 North America and South America. 



3. Digitaria ischaemum (Schreb.) 

 Schreb. ex Muhl. Smooth crabgrass. 



