72 FLORA. 



unexplained.] A monotypic genus, native of tropical and temperate regions of 

 the Old World. 



i. Nazia racemosa (L.) Kuntze. PRICKLE-GRASS. (I. F. f. 226.) Culms 

 5-35 cm. tall, pubescent above. Leaves 2.5-7.5 cm. long, rather strongly ciliate; 

 spike 2.5-10 cm. long, sometimes partially included in the somewhat inflated upper 

 sheath; second scale coriaceous, 3 mm. long, 5-nerved; third scale 2 mm. long, 

 I -nerved. Occasional in ballast and waste places about the seaports. July-Sept. 



9. PA3PALUM L. (See Appendix.) 



Perennial grasses, various in habit, with generally flat leaves and I -flowered 

 spikelets, borne singly or in pairs in 2 rows on i-sided spikes, which are single, in 

 pairs or panicled. Spikelets oblong to orbicular, flat on the outer surface, convex 

 on the inner. Scales 3, 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. [An ancient Greek name for some grass, 

 used by Hippocrates.] About 160 species, of wide distribution in tropical and 

 temperate regions, most abundant in America. 



Rachis of the racemes very broad, twice the width of the spikelets, or nearly so, which 



are partially concealed by its inrolled margins. 

 Rachis extending beyond the spikelets, long-acuminate; spikelets about i mm. long. 



1. P. mucronatum. 

 Rachis not extending beyond the spikelets, acute ; spikelets 2 mm. long. 



2. P. membranaceum. 

 Rachis of the racemes narrower than the spikelets, not inrolled on the margins. 



Racemes 2, approximately in a pair at the summit of the culm ; rootstocks exten- 

 sively creeping ; culms not tufted. 3. P. distichum. 

 Racemes i-several, alternate ; culms tufted. 



Culms simple, no branches from the upper sheath ; racemes stout. 

 Spikelets obtuse, glabrous. 



Spikelets 3 mm. or less long. 



Leaves very hirsute on both surfaces ; the hairs on the sheaths very 



dense and long. 4. P, plenipilum. 



Leaves glabrous beneath, or nearly so. 



Spikelets elliptic, hence longer than broad, decidedly convex 

 on the inner side ; sheaths glabrous or nearly so. 



5. P. laeve. 



Spikelets orbicular, or nearly so, hence as broad as long, but 

 little convex on the inner side ; sheaths hirsute. 



6. P. circulare. 

 Spikelets 4 mm. or more long. 7. P. glabrattim. 



Spikelets acute, long villous-ciliate on the margins. 



8. P. dilatatum. 

 Culms branched, the upper sheath containing from 1-3 branches; racemes 



slender. 

 Leaves glabrous on both surfaces, or the midnerve sometimes pubescent 



beneath. 



Sheath margins glabrous. 9. P. ciliatifolium, 



Sheath margins pubescent. 



Spikelets orbicular, hence as broad as long, straw-color, 2 mm. in 



diameter. 10. P. stramineum. 



Spikelets broadly obovate to oval, longer than broad, green, 1.5 mm. 

 long. n. P. longipedunculatum. 



Leaves pubescent on both surfaces. 



Pubescence of copious soft short -appressed hairs. 



Culms prostrate, the lower leaves i dm. or less long. 



12. P. prostraturn. 

 Culms erect, the lower leaves 1.5 dm. or more long. 



13. P. Bus /tit. 

 Pubescence of more or less spreading and usually rather long stout hairs. 



Culm densely pilose below the racemes ; lower sheaths usually 



glabrous or nearly so. 14. P. pubescens. 



Culm glabrous ; lower sheaths generally hirsute. 



Spikelets 1-1.5 mm. long. 15. P. setaceunt. 



Spikelets 2-2.25 mm. long. 



Racemes on the main culm i, or sometimes 2 ; spikelets 



glabrous ; leaves rather thin. 16. P. Muhlenbergii. 

 Racemes on the main culm 2 or 3 ; spikelets pubescent; 

 leaves thick. 17. P. dasyphyllum. 



