126 



GRAMINEAE. 



Vol. I. 



P. mucronatum. 

 P. dissectum. 



of the outermost, the outer ones membranous, the inner one indurated and subtending a 

 palet and perfect flower. Stamens 3. Styles separate ; stigmas plumose. Grain ovoid or 

 oblong, free. [Greek name for some grass, used by Hippocrates.] 



About 160 species, widely distributed in tropical and temperate regions, most abundant in 

 America. Type species : Panicum dissectum L. 



Wings of the rachis broad, membranous, inrolled on the spikelets. 



Racemes 20 or more; spikelets elliptic, acute, about yi," long, pubescent. 

 Racemes less than 10; spikelets oval, obtuse, 1" long or more, glabrous. 2. 

 Wings of the rachis narrow, not membranous nor inrolled on the spikelets. 



Racemes i-many, never conjugate at the summit of the culm, always distant one from the other. 

 One to several raceme-bearing naked branches arising from the uppermost leaf-sheath. 

 Leaf-blades glabrous on the lower surface, midnerve sometimes sparsely pubescent. 

 Spikelets about 54" long ; leaves more numerous at the base of the stem. 



3. P. longipedunculatum. 

 Spikelets 1" long or more; leaves scattered. 



Blades firm, appressed-pubescent on the upper surface with short hairs. 



4. P. stramineum. 

 Blades thin, membranous, glabrous on the upper surface. 



Leaf-blades densely pubescent on both surfaces. 

 Pubescence of copious soft short appressed hairs. 

 Stems prostrate ; lower leaf-blades 4' long or less. 

 Stems erect ; lower leaf-blades 6' long or more. 

 Pubescence of long stiff spreading hairs. 

 Culms long-hirsute below the racemes. 

 Culms glabrous. 



Spikelets less than 1" long. 

 Spikelets over 1" long. 



Racemes on the main culm 1, or sometimes 



not thick. 

 Racemes on the main culm 2 or 3 ; 

 blades thick. 

 No branches arising from the uppermost leaf-sheath. 



Spikelets rounded or obtuse at the apex ; not ciliate on the margins. 

 Spikelets ij4" long or less. 



Fruiting scale white to yellowish. 

 Spikelets singly disposed. 



Spikelets oval, l /i as thick as broad or more, the outer scales firm. 



Leaf-sheaths glabrous, or sometimes ciliate on the margins ; blades glabrous, or 



sparingly hirsute on the upper surface. 12. P. laeve. 



Leaf-sheaths as well as the blades hirsute. 13. P. plenipilum. 



Spikelets circular or nearly so, 'J-$ as thick as broad, the outer scales thin and 



5. P. ciliatifolium. 



6. P. psammophilum. 



7. P. Bushii. 



8. P. pubescens. 



9. P. setaceum. 



spikelets glabrous ; leaf-blades 

 10. P. Muhlenbergii. 

 spikelets usually more or less pubescent ; leaf- 

 P. debile. 



usually wrinkled. 

 Spikelets in pairs. 

 Fruiting scale deep seal brown. 

 Spikelets more than 1^" long. 



Leaf-blades short, the larger ones usually 6' 



Leaf-blades long, exceeding 8' ; racemes long. 

 Spikelets acute, ciliate with very long hairs. 

 Racemes conjugate at the summit of the culm, rarely 

 distance below. 



14. P. circulare. 



15. P. laeviglume. 



16. P. Boscianum. 



long or less ; racemes short. 



17. P. difforme. 



18. P. floridanum. 



19. P. dilatatum. 

 3's or with an additional one ; 



20. P. distichum. 



short 



i. Paspalum mucronatum Muhl. Water Paspalum. Fig. 288. 



Paspalum paniculatum Walt Fl. Car. 75. 1788. Not L. 



1759- 

 Paspalum mucronatum Muhl. Cat. 8. 181 3. 

 Cercsia fluitans Ell. Bot. S. C. & Ga. 1 : 109. 1817. 

 Paspalum fluitans Kunth, Rev. Gram. 24. 1829.. 



Culms ascending, 6'-$° long, from a floating or creep- 

 ing base, branched. Sheaths very loose or inflated, 

 smooth or scabrous, glabrous or pubescent ; blades 3'- 

 12' long, \'-\' wide, acuminate, scabrous ; racemes 20- 

 100, J'-s' long, alternate or whorled, slender; rachis 

 flat, thin, exceeding the spikelets, long-acuminate, 

 scabrous, its margins nearly enclosing the spikelets; 

 spikelets in two rows, V-\" long, elliptic, pubescent; 

 outer scales very thin, 2-nerved, the first one usually a 

 little the longer. 



In water or on mud. Virginia to southern Illinois and 

 Missouri, south to Florida and Texas. Also in tropical 

 America. Sept. 



