928 



CXLTII. GE AMINES. 



Grain free but tightly enclosed by the hardened glume and palea, oblong, 

 ellipsoid or lanceolate. — Disteib. Species 200-250, chiefly in the warm 

 regions of the world. 



Spikelets dorsally compressed or subterete. 



Inflorescence racemose, of simple (rarely branched) spikes 

 or racemes bearing secund spikelets. 

 Rhachis of spikes broad, flattened. 

 Spikelets 2-seriate. 



Spikes shorter than the internodes 1. P.flavidum. 



Spikes longer than the internodes, 



Upper floral glume granulate 2. F. punctatum. 



Upper floral glume smooth 3. P. Jluitans. 



Spikelets S-o-seriate; lower floral glume cuspidate 

 or awned. 



Stems stout, reaching 5 ft. long ; lower floral 



glume awned 4. P. stagnimim. 



Stems slender, decumbent, 1-2 ft. long; lower 



floral glume cuspidate, not awned 5. P. colonum. 



Ehachis of spikes narrow and filiform, terete or 

 angular. 



Lower invol.-glume minute, not i as long as the 

 upper floral glume, nerveless. 



Leaf-base rounded ; lower invol.-glume 



triangular 6. P. Isachne. 



Leaf- base cordate - amplexicaul ; lower 



invol.-glume semilunate 7. P. prostratiim. 



Lower invol.-glume from ^-^ as long as the 

 upper floral glume, 3-5-nerved. 



Upper floral glume apiculate or awned. 

 Upper floral glume only apiculate. 

 Lower invol.-glume ovate, acute, ^ as 



long as the upper floral glume 8. P. ramosum. 



Lower invol.-glume orbicukr, about 



5 as long as the upper floral glume . 9. P. setigencm. 

 Upper floral glume abru2:itly awned ; 

 lower invol.-glume rather less than ^ 



the lower floral glume 10. P.javanicum. 



Inflorescence of spiciform or effuse panicles. 

 Panicles narrow, spiciform. 



Lower invol.-glume very minute ; spikelets 



lanceolate 11. P. interrwphim. 



Lower invol.-glume \ as long as the upper ; spikelets 



globosely ovoid 12. P . myosuroides. 



Panicles broad, effuse. 



Lower invol.-glume as long as the lower floral glume 



or nearly so 13. P. turgidum. 



Lower invol.-glume shorter than the lower floral 

 glume. 

 Annuals. 



Leaves ^ in. broad ; panicle 15 in. long 14. P. obscurant. 



Leaves ^-^ in. broad ; panicle 4-10 in. l»ng . 15. P. trypheron. 

 Perennials. 



Lower invol. -glumes very minute, 1 or rarely 



both often obsolete IG. P. subeglumc. 



Lower invol.-glumes distinctly evident. 



Spikelets laxly clustered on the branches... 17. P. antidotale. 

 Spikelets solitary (rarely 2-nate). 



Lower invol.-glume not \ the length of 



the upper, orbicular or reniform 18. P. proUferttm 



var. paludosum. 

 Lower invol.-glume ^ the length of the 



upper, ovale, subacute 19. P. moniaiiunt. 



Spikelets strongly laterally CDiupressed, gibbously ovuid ... 20. P. pa/ciia. 



