PANICEJE 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; ligule 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 }/% 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 % 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-f ringed. The plant is often pur- 

 plish 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. isch&mum (Schreb.) Nash (Digitaria 

 humifusa Pers.; Syntherisma linearis Nash; S. glabrum 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 



