Tm; (iKAssKs ok Tknnksskk. 29 



nearly so, and usually as lon-^ as the cartilaginous third ^liune 

 whicli encloses a i)alea of similar texture and a hermaphrodite 

 tlower. (irain oblonjj. enclosed with the indurated fruitinj^ j^lume 

 and i)alea. 



Perennials, very variable in habit, usually j^rowinj^ in moist 

 j^^rounds. Species about one hundred and sixty, widely distrib- 

 uted, especially abundant in the tropical rei^ions of America. 

 There are about forty species and varieties in the United States, 

 chiefly in the Southern districts. The following have been found 

 within the wState. 



KF.V TO THE SPECIKS. 



I. Rachis of the racemes thin and membranous, the mar- 

 gins nearly covering the small, two-rowed spikelets . . 2 



1. Rachis firm, narrower than the two to four-rowed spikelets 3 



2. Rachis projecting beyond the spikelets 1. P. mucronatum. 



2. Rachis not extending l)eyond the spikelets 



2. P. MEMr.RANACEUM. 



3. Plants extensively creeping, racemes digitate 4 



3. Plants not extensively creeping, racemes solitary or scat- 



tered along the main axis 5 



4. Racemes in pairs at the apex of the culm, widely spreading, 



spikelets i )4 lines long acute .... 3. P. distichum. 



4. Racemes 2 to 6, very slender, erect or ascending, spikelets i 



line long 4. P. compressum. 



5. Spikelets acute, the margins of the lower glume conspicu- 



ously hairy 5- P- imlatatum 



5. Spikelets obtuse, outer glumes smooth or nearly so .... 6 



6. Rachis flat on the back, about a line wide, its margins 



nearly straight, spikelets mostly four-rowed 7 



6. Rachis narrower, undulating or flexuose, spikelets for the 



most part two-rowed 8 



7. Culms branching only near the base, racemes 3 to 7, spike- 



lets 1^4 lines long, flowering glume green 



6. P. PUBIFLORUM. Var. GLABRUM. 



7. Culms branched above, racemes three to twelve, spikelets one 



line long, flowering glume dark brown and punctate-dot- 

 ted 7. P. BOSCIANUM. 



8. Racemes 2 to 6, rather stout, spikelets one and one-half to 



two lines long 9 



8. Racemes often solitary, very slender, on long-exserted ter- 



minal and frequently lateral peduncles, spikelets one 

 line or less long 10 



9. Culms 3 to 5 feet high, racemes erect or ascending, spikelets 



two lines long 8. P. Floridanum. 



9. Culms I to 3 feet high, racemes spreading, spikelets one and 



one-half lines long 9. P. l.eve. 



10. Leaves 5 to 12 inches long, spikelets one line long, floral 



glumes with a distinct depression on the back near the 



base 10. P. CILIATIFOLIUM. 



