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



Figure 1585.— Pennisetvm 

 villosum, X H. (Eastwood 172, 

 Calif.) 



Figure 1586. 

 pelii, X Vi. 



—Pennisetum rup. 

 (Hitchcock, D.C.) 



gate, scabrous; panicle 15 to 35 cm long, nodding, pink or purple; 



fascicles peduncled, rather loosely arranged, containing 1 to 3 spike- 

 lets; bristles plumose toward base, unequal, 

 the longer 3 to 4 cm long. % — Cultivated 

 for ornament, especially as a border plant or 

 around fountains. Introduced from Africa. 

 Referred by some to P. setaceum (Forsk.) 

 Chiov., a dubious name. 



Pennisetum macrosta- 



chyum (Brongn.) Trin. 



Resembling P. ruppelii; 



blades as much as 2.5 cm 



wide; panicle denser, brown- 

 ish purple, fascicles smaller; 



bristles not plumose. 21 



— Cultivated sparingly for 



ornament. East Indies. 

 Pennisetum alopecu- 



roides (L.) Spreng. Peren- 

 nial; culms tufted, slender, 



60 to 120 cm tall, pubescent 



below the panicle; blades 



long, narrow; panicle 5 to 



20 cm long, tawny to purple; 



bristles prominent, often 



purple, scabrous. % (P. 

 japonicum of gardens.) — Occasionally cultivated for 

 ornament. China. 



Pennisetum latifolium Spreng. Perennial; culms 100 to 150 cm tall, the 

 nodes appressed-pubescent; blades 2 to 3 cm wide, tapering to a long point; 

 panicles terminal and axillary, nodding, 5 to 8 cm long, the bristles prominent. 

 21 — Occasionally cultivated for ornament. South America. 



137. CENCHRUS L. Sandbur 



Spikelets solitary or few together, surrounded and enclosed by a 

 spiny bur composed of numerous coalescing bristles (sterile branch- 

 lets), the bur subglobular, the peduncle short and thick, articulate at 

 base, falling with the spikelets and permanently enclosing them, the 

 seed germinating within the old involucre, the spines usually retrorsely 

 barbed. Annuals or sometimes perennials, commonly low and 

 branching, with flat blades and racemes of burs, the burs readily 

 deciduous. Type species, Cenchrus echinatus. Name from Greek 

 kegchros, a kind of millet. 



The species are excellent forage grasses before the burs are formed. 

 Several species are weeds and become especially troublesome after 

 the maturity of the burs. 

 Involucral lobes united at the base only. Racemes dense; plants perennial. 



1. C. MYOSUROIDES. 



Involucral lobes united above the base. 



Involucre with e ring of slender bristles at base. Plants annual. 



Burs, excluding the bristles, not more than 4 mm wide, numerous, crowded 

 in a long raceme; lobes of the involucre interlocking, not spinelike. 



2. C. VIRIDIS. 

 Burs, excluding the bristles, 5 to 7 mm wide, not densely crowded; lobes of 

 the involucre erect or nearly so or rarely one or two lobes loosely inter- 

 locking, the tips spinelike 3. C. echinatus. 



Involucre with flattened spreading spines, no ring of slender bristles at base. 

 Body of bur ovate, usually not more than 3.5 mm wide, tapering at base; 

 plants perennial. 



Burs glabrous; spines 4 to 6 mm long 4. C. gracillimus. 



Burs pubescent; spines rarely more than 4 mm long, usually shorter. 



5. C. INCERTUS. 



