GRAMINEAE (GRASS FAMILY) 



97 



larger, glumes many-nerved ; sterile lemma subrigid ; 

 fertile lemma and palea much indurated, acuminate, 

 margins of lemma neither hyaline nor inrolled. Erect 

 annuals or perennials with flat leaves. (Name from 

 dfj,<f>tKapiros, doubly fruit-bearing.} 



1. A. Purshii K until. Annual ; culms erect, branch- 

 ing, 3-6 dm. high; sheaths and blades coarsely hispid; 

 terminal panicle contracted ; spikelets about 4 mm. long ; 

 fertile spikelets solitary, about 6 mm. long, at the ends 

 of the slender subterranean branches. (Milium Amphi- 

 carpon Pursh ; A. Amphicarpon Nash.) Moist sandy 

 pine barrens, N. J. to Fla. Sept. FIG. 66. 



9. PASPALUM L. 



56. A. Purshii. 

 Sterile spikelet closed x 2. 

 Same wide open x 2. 

 Basal fertile spikelet, 

 partly open x 2. 



Spikelets 1 -flowered, plano-convex, nearly sessile, solitary or in pairs, in 2 

 rows on one side of a continuous narrow or dilated rhachis, forming simple spike- 

 like racemes ; spikelets placed with the back of the fertile lemma toward the 

 rhachis ; first glume obsolete (rarely present) ; lemma and palea chartaceous- 

 indurated, margins of the lemma inrolled. Perennials, with 1-several racemes 

 digitate or racemose at the summit of the culm and branches. (IIa<nrd\os, a 

 Greek name for millet.) 



a. Racemes 1-several, 1 terminal and often 1 or more lateral &. 

 6. Rhachis membranaceous, 2 mm. or mojfe broad. 



Spikelets 1.5 mm. long, elliptical, pubescent . . . . 1. P. mucronatum. 



Spikelets 2 mm. long, oval, glabrous 2. P. dissectum. 



b. Rhachis narrow, not membranaceous, less than 1 mm. broad 



(except in P. Boscianum) c. 

 c. Axillary peduncles 1 or more from uppermost sheath ; leaves 



ciliate on the margin d. 

 d. Spikelets 2 mm. long e. 



e. Leaves glabrous on both surfaces 



e. Leaves pubescent on one or both surfaces /. 

 /. Spikelets glabrous. 



Leaves densely long-pubescent. 



Culm hirsute below raceme 



Culm glabrous 



Leaves puberulent and sometimes sparsely villous . 

 /. Spikelets pubescent ; leaves short-pubescent. 



Culms erect 



Culms prostrate 



d. Spikelets 1.5 mm. long. 



Spikelets glabrous 



Spikelets pubescent 



c. Axillary peduncles none g. 

 g. Spikelets glabrous h. 



h. Spikelets singly disposed so as to appear in 1-2 rows. 

 Spikelets 2.5 mm. long. 

 Plants glabrous or sparingly pilose. 

 Leaf-blades of culm 1-2 dm. long ; racemes 3-5 



cm. long 



Leaf-blades of culm 2-4 dm. long; racemes 8-10 



cm. long 12. P. 



Plants with pubescent sheaths and blades . . . 13. P. plenipilum 

 Spikelets 3 mm. long; sheaths papillose-hirsute . . 14. P. circular e. 

 Spikelets 4 mm. long. 

 Leaf-blades less than 1.5 dm. long . . . . 16. P. difforme. 



Leaf-blades 2-4 dm. long 15. P. floridanum. 



h. Spikelets in pairs so as to appear in four rows. 



Spikelets stramineous at maturity 17. P. laemfflume. 



Spikelets dark brown at maturity 18. P. Bosciamim. 



g. Spikelets ciliate 19. P. dilatatum. 



Racemes a pair at the summit of the culm . . . . .20. P. distichum. 



5. P. ciliatifoUum. 



6. P. pubescens. 

 T. P. MuJilenbergii. 

 8. P. stramineum. 



9. P. Bushii. 



10. P. psammophilum. 



3. P. longipedunculatum. 



4. P. setaceum. 



11. P. laeve. 



** Racemes with a broad, thin-membranaceous, or foliaceous and keeled, rhachis, 



F" mm. wide or more, the incurved margins partly inclosing the small 2-rowed 

 oikelets. (Aquatic or nearly so, decumbent or floating.} 

 P. mucronatum Muhl. Sheaths papillose-hirsute or nearly smooth, in- 

 ; blades lanceolate, 2.5-15 cm. long, 6-14 mm. wide, scabrous ; racemes 

 , finally spreading ; rhachis extending beyond the spikelets, which are ellip- 



GRAY'S MANUAL 7 



