MANUAL OF THE GRASSES OF THE UNITED STATES 



2. Trichachne californica (Benth.) 

 Chase. Cottontop. (Fig. 824.) Culms 

 erect from a knotty swollen felty- 

 pubescent base, 40 to 100 cm. tall; 

 leaves numerous, the sheaths gla- 

 brous to sparsely pilose ; blades mostly 

 less than 12 cm. long, 3 to 5 mm. 

 wide, from nearly glabrous to densely 

 puberulent; panicle mostly 5 to 10 

 cm. long, the few racemes usually 3 

 to 5 cm. long, occasionally longer, 

 erect or nearly so; spikelets approxi- 

 mate, excluding the hairs 3 to 4 mm. 

 long, the white to purplish hairs much 

 exceeding them, often spreading, the 

 middle internerves of the sterile 

 lemma glabrous. % (T. saccharata 

 Nash.) — Plains and dry open ground, 

 Texas and Oklahoma to Colorado, 

 Arizona, and Mexico; South America. 



3. Trichachne patens Swallen. (Fig. 

 825.) Culms tufted, erect, 40 to 90 

 cm. tall; sheaths more or less papil- 

 lose-pilose, the lowermost densely 

 f elty-pubescent ; blades 5 to 15 cm. 

 long, 1 to 4 mm. wide, scabrous; pan- 

 icle 10 to 18 cm. long, the racemes 

 stiffly ascending or spreading; spike- 

 lets remote, 4 mm. long, densely silky, 

 the hairs exceeding the spikelet; fruit 

 3 mm. long, acute. % — Dry fields, 

 prairies, and roadsides, Texas. 



4. Trichachne hitchcockii (Chase) 

 Chase. (Fig. 826.) Culms tufted and 

 branching at base, leafy below, slen- 

 der, 30 to 50 cm. tall; sheaths and 



573 



Figure 824. — Trichachne californica, X 1. (Hitchcock 

 13608, Tex.) 



blades nearly glabrous to puberulent, 

 sometimes densely so toward base, 

 the blades 2 to 5 cm. long, 2 to 3 mm. 

 wide; panicle long-exserted, 6 to 10 

 cm. long, the few racemes 3 to 4 cm. 

 long, mostly rather remote and erect ; 

 spikelets 2.5 to 3 mm. long, densely 

 silky-villous, the prominent nerves not 

 hidden, the grayish hairs not exceed- 

 ing the spikelet. % — Dry plains, 

 Texas; northern Mexico. 



129. DIGITlRIA Heister. Crabgrass 



{Syniherisma Walt.) 



Spikelets in twos or threes, rarely solitary, subsessile or short-pediceled, 

 alternate in 2 rows on one side of a 3-angled winged or wingless rachis; spikelets 

 lanceolate or elliptic, nearly planoconvex; first glume minute or wanting; 

 second glume equaling the sterile lemma or shorter; fertile lemma carti- 

 laginous, the hyaline margins pale. Annual or perennial, erect to prostrate, 

 often weedy grasses, the slender racemes digitate or approximate on a short 

 axis. Type species, Digitaria sanguinalis. Name from Latin digitus, finger, 

 alluding to the digitate inflorescence of the type species. 



The species are in the main good forage grasses. Digitaria sanguinalis, the 

 common crabgrass, is a weed in cultivated soil. In the Southern States, where 

 it produces an abundant growth in late summer on fields from which crops 

 have been gathered, it is utilized for forage and is sometimes cut for ha}^ 

 This species and D. ischaemum are common weeds in lawns. They form a fine 

 green growth at first but start late and die in the fall. 



