14 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



bearing at the apex in a slight crateriform excavation a tuft of woolly hairs, 

 the palea concave below, gibbous above, the apex often free at maturity. 



All the species of Lasiacis have woody culms except L. procerrima. The 

 spikelets differ from those of Panicum in the bony obovoid fruit, pubescent at 

 the apex, the palea concave below and gibbous above. 



KEY TO THE SPECIES. 



Culms erect, simple, herbaceous ; blades as much as 40 cm. long and 5 cm. wide. 



deeply cordate-clasping 1. L. procerrima. 



Culms much branched, woody ; blades mostly less than 20 cm. long, narrowed 

 at base or somewhat cordate. 

 Main stem prostrate, the fertile shoots prostrate, ascending, or erect. 

 Blades lanceolate, mostly less than 5 cm. long; fertile shoots strongly 



dorsiventral, mostly prostrate 2. L. rugelii. 



Blades linear-lanceolate, about 10 to 12 cm. long ; fertile shoots ascending or 



erect from a decumbent base, not dorsiventral 3. L. grisebachii. 



Main stem clambering, or much branched and forming a tangled mass. 

 Ligule noticeable, brownish, about 2 mm. long. 

 Blades glabrous beneath, scabrous on both surfaces, elongate, more than 

 10 times as long as wide ; plants not forming a strong central 



clambering cane 4. L. oaxacensis. 



Blades puberulent beneath, glabrous or scabrous above, less than 10 

 times as long as wide; plants forming a strong central clambering 



cane 5. L. ligulata. 



Ligule inconspicuous, hidden within the mouth of the sheath, rarely as 

 much as 1 mm. long. 

 Plants not high-climbing, decumbent and rooting at base, forming a 

 tangled mass, with no strong central cane ; spikelets clustered toward 



the ends of the branches 6. L. rhizophora. 



Plants high-climbing, forming a strong central cane; spikelets not clus- 

 tered toward the ends of the branches. 

 Blades glabrous on both surfaces, often more or less scabrous. (See 

 L. rusci folia, this rarely with glabrous ovate-lanceolate blades.) 

 Main culm papillose-hispid; lateral flowering branches glabrous; 



panicles small and narrow 7. L. leptostachya. 



Main culm (except sometimes the young shoots) glabrous. 

 Blades narrow, usually 3 to 4 mm., sometimes 5 mm., wide, 8 to 



10 cm. long 8. L. harrisii. 



Blades more than 5 mm. wide, if as much as 10 cm. long. 



Panicle few-flowered, 5 to 10 cm. long ; branches strongly zigzag. 

 the branchlets strongly divaricate or reflexed; blades nar- 

 rowly lanceolate, firm, mostly less than 1 cm. wide (some- 

 times wider on vigorous shoots) 9. L. divaricata. 



Panicles many-flowered, usually 15 to 25 cm. long or more on 

 the primary branches; branches straight or arcuate, not 

 zigzag; blades mostly over 1.5 cm. wide. 



Spikelets globose, about 3 mm. long 10. L. globosa. 



Spikelets lanceolate-ellipsoidal, 3.5 to 5 mm. long. 



Spikelets 4.5 to 5 mm. long, on short stiff appressed pedi- 

 cels ; blades oblong-ovate or elliptic-lanceolate. 



11. L. sloanei. 

 Spikelets 3.5 to 4 mm. long, on flexuous spreading pedicels ; 

 blades lanceolate or nari-owly-lanceolate. 



12. L. patentiflora. 



