112 



POACEAE 



8. PANICUM L. Sp. PL 55. 1753. 



Spikelets more or less compressed dorsally, arranged in open or compact panicles, rarely 

 in racemes ; glumes 2, herbaceous, nerved, usually very vmequal, the first often minute, the 

 second typically equaling the sterile lemma, the latter of the same texture and simulating a 

 third glume, bearing in its axil a membranaceous or hyaline palea and sometimes a staminate 

 flower, the palea rarely wanting ; fertile lemma chartaceous-indurated, typically obtuse, the 

 nerves obsolete, the margins inrolled over an inclosed palea of the same texture. Annual 

 or perennial grasses of various habit. [An ancient Latin name for the Italian millet, Cliaeto- 

 chloa italica.] 



Species probably about 500, confined to the warmer regions of Iiotli hemispheres. Type species, Panicum 

 miliaceum L. 



Plants annual. 



Fruit (mature fertile lemma) transversely rugose. 1. P. ariconiciim. 



Fruit smooth. 



First glume not over one-fourth the length of the spikelet, tnmcate or broadly triangular; sheaths 



smooth. 2. P. dicliotomiflorum. 



First glume as much as half the length of the spikelet, acute or acuminate; sheaths hispid. 

 Panicle erect. 



Panicle more than half the length of the entire plant. 



Spikelets 2-2.5 mm. long. 3. P. capillare. 



Spikelets about 3 mm. long. 4. P. barbipulvinaium. 



Panicle not more than one-third the entire height of plant; spikelets 2.7-3.3 mm. long. 



5. P. hirticaule. 

 Panicle drooping. 

 Plants perennial. 



Spikelets 6-7 mm. long. 

 Spikelets less than 4 mm. long. 



Spikelets not turgid nor strongly nerved, pubescent, not over 2.6 mm. long. 

 Spikelets not over 2 nun. long. 



Blades glabrous on both surfaces. 

 Blades pubescent, at least below. 



Plants more or less pubescent but not velvety. 

 Vernal blades pubescent above. 



Upper surface of blades appressed-pubescent; autumnal form erect or ascending 



9. P. huachucae. 

 Upper surface of blades pilose; autumnal form decumbent-spreading. 



10. P. pacificum. 

 Vernal blades glabrous above. 11. P. occideiitale. 



Plants velvety-pubescent. 12. P. thermale. 



Spikelets about 3 mm. long. 13. P. shastense. 



Spikelets turgid, strongly nerved, sparsely hispid, spikelets 3.2-3.3 mm. long. 



14. P. scribneriannm. 



1. Panicum arizonicum Scribn. & Merr. 



6. P. rniiiacenm. 



7. P. iirvilleannm. 



8. P. lindheimeri. 



Arizona Panicum. 



Fig. 229. 



Panicmu arizonicum Scribn. S: Merr. U. S. Dept. Agr. Div. 



Agrost. Circ. 32: 2. 1901. 



Annual ; culms usually branching from the base, 

 glabrous except below the panicle, 20-60 cm. tall ; 

 nodes sometimes slightly pubescent ; sheaths glabrous 

 to strongly papillose-pubescent; blades 5-15 cm. long. 

 6-12 mm. wide, glabrous or papillose-hispid beneath ; 

 panicles long-exserted, finely pubescent and copiously 

 papillose-hirsute, 7-20 cm. long, the branches soli- 

 tary, ascending, few-flowered ; spikelets nearly 4 mm. 

 long, obovate-elliptical, abruptly pointed, densely hirsute 

 to glabrous, borne on very short appressed branchlets. 



Open ground, Sonoran Zones; Jamacha, California, to western 

 Texas and south to Oaxaca. July. Type locality: Arizona. 



2. Panicum dichotomiflorum Alichx. 

 Smooth Witch-grass. Fig. 230. 



Panicum dicliotomiflorum Michx.'Fl. Bor. Am. 1: 48. 1803. 

 Annual, usually much-branched from a geniculate 

 l)ase, smooth throughout; culms rather succulent, 

 60-90 cm. tall ; blades 10-50 cm. long, about 1 cm. 

 wide; panicles 10-30 cm. long, finally spreading; 

 spikelets 2.5 mm. long, narrowly oblong-ovate, 

 acute, faintly 7-nerved, the first glume short, 

 truncate, about one-fourth the length of the spikelet. 



Low ground and cultivated soil. Fresno (Bioletti). Com- 

 mon in eastern United States. Tyiie locality: Allegheny 

 Mountains. 



