PANICS^ 181 



species in particular, S. sanguinalis, is a well-known weed 

 under the name of crab-grass. This and S. ischcemum 

 are troublesome weeds in lawns. Being annuals, they die 

 out and leave unsightly brown patches. Crab-grass is 

 often utilized for hay in the southern states. (Digi- 

 taria Hall.) 



Syntherisma sanguinalis (L.) Dulac. (Fig. 20). Crab-grass. 

 Crop-grass. Annual; culms becoming much branched at base, 

 decumbent or prostrate and rooting at the nodes, the flowering 

 branches ascending, sometimes as much as 3 or 4 feet long ; sheaths 

 hirsute, with hairs arising from papillae, sometimes nearly glabrous 

 except near the nodes; hgule about 1 mm. long, thin and membra- 

 naceous, blades flat and thin, more or less hirsute like the sheaths, 2 

 to 6 inches long and as much as K inch wide; panicle consisting of 

 few to several slender spikes, 3 to 6 inches long, a few digitate at 

 the summit of the culm, with usually several others below in a more 

 or less distinct whorl; rachis flat, winged on the margins, about 1 

 mm. wide, bearing on one side the appressed crowded spikelets, 

 these in pairs, one nearly sessile, the other with a sharply triangular 

 pedicel about half as long as the spikelet; spikelets flattened dor- 

 sally, elliptical-lanceolate, about 3 mm. long, the first glume small, 

 nerveless, about 14 mm. long, the second glume lying next to the 

 axis^ narrow, about half as long as the spikelet, appressed-villous, 

 the sterile lemma distinctly 3-nerved, as long as the spikelet, the 

 lateral nerves more or less ciliate-fringed. The plant is often pur- 

 phsh tinged, and the species is variable in size and habit accord- 

 ingly as it grows in rich or poor soil, in the open or among other 

 plants. 



A related species, S. ischsemum (Schreb.) Nash {Digitaria 

 hu7nifusa Pers.; Syntherisma linearis Nash; S. glahrum Schrad.), 

 is common in the eastern United States. This species can be dis- 

 tinguished from the preceding by its being glabrous or nearly so, 

 by the smaller spikelets, and by the absence of the first glume. 



217. Panicum L. — This large genus of probably 400 

 species is distributed throughout all warm regions. The 

 spikelets are usually arranged in panicles. They consist of 



