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



times with one or more corms of previous years attached; sheaths 

 glabrous, or pilose toward the summit; blades 25 to 60 cm long, 3 to 

 12 mm wide, scabrous above, glabrous beneath; panicle 20 to 50 cm 

 long, open; spikelets 3.5 to 4.2 mm long. % — Moist places in can- 

 yons and valleys, western Texas to Arizona; Mexico (fig. 1508). 



Figure 1506. — Panicum plenum. Two 

 views of spikelet, and floret, X 10. 

 (Type.) 



Figure 1507.— Panicum bulbosum. Base of culm, 

 X Vi, two views of spikelet, and floret, X 10. (Lem- 

 mon 2914, Ariz.) 



Panicum bulbosum var. minus Vasey. Culms slender, mostly 

 less than 1 m tall, the corms smaller than in the species; blades mostly 

 2 to 4 mm wide; spikelets 2.8 to 3.2 mm long. % (P. bulbosum 

 var. sciaphilum Hitchc. and Chase.) — Same range as species and 

 more common with us. 



8. Virgata. — Perennials from stout rhizomes; culms mostly stout; 

 ligules membranaceous, ciliate; blades linear, mostly firm; 

 spikelets turgid, usually gaping, strongly 5- to 9-nerved, glabrous, 

 pointed; lower floret usually staminate; fruit smooth and shining. 



140. Panicum repens L. (Fig. 1509.) Culms rigid, 30 to 80 cm 

 tall, erect from the nodes of strong horizontal often extensively 

 creeping rhizomes, clothed at base with blade- 

 less sheaths; sheaths more or less pilose; blades 

 flat or folded, 2 to 5 mm wide, sparsely pilose 

 to glabrous; panicle open, 7 to 12 cm long, the 

 somewhat distant branches stiffly ascending; 

 spikelets 2.2 to 2.5 mm long, ovate; first 

 glume about one-fifth as long as the spikelet, 

 loose, truncate. % — Sea beaches along the 

 Gulf coast, Florida to Texas (fig. 1510); 

 tropical and subtropical coasts of both hemispheres, probably intro- 

 duced in America. 



141. Panicum gouini Fourn. (Fig. 1511.) Resembling P. repens, 

 but the culms usually less than 30 cm tall; sheaths and blades usually 

 glabrous; panicle smaller, more densely flowered; first glume longer. 

 ^ —Sea beaches, Alabama to Louisiana ; Gulf coast of Mexico 



142. Panicum virgatum L. Switchgrass. (Fig. 1512.) Plants 

 usually in large bunches, green or glaucous, with numerous scaly 

 creeping rhizomes; culms erect, tough and hard, 1 to 2 m tall; sheaths 

 glabrous; blades 10 to 60 cm long, 3 to 15 mm wide, flat, glabrous, or 

 sometimes pilose above near the base, rarely pilose all over; panicle 

 15 to 50 cm long, open, sometimes diffuse; spikelets 3.5 to 5 mm long, 



Figure 1508.— Distribution of 

 Panicum bulbosum. 



