24 



This plant, lias been referred to the South American TrisUtdii/a leiostachya Nees, from 

 which it is readily distinguished by its more slender habit, plane, not involute 

 leaves, and shorter spikelets and awns. The spikelets of T. leiosiachya are 5 cm. 

 long and the awns are about 12 cm. long. In T. avenacea the spikelets are from 

 2 to 3.5 cm. long and the awns do not exceed 6 cm. in length. 

 Near Santa Teresa, Sierra ]Madre Mountains, Territorio de Tepic, 2229 J. N. Eose, 



August 13, 1897. 

 TRISTACHYA LAXA Scribn. & Merrill, sp. nov. (Fig. 7.) 



A stout, erect perennial, 15 to 20 dm. high, with long leaves, scabrous spikelets, and 



. very lax panicles 4 to 5 

 dm. in length. Culms 

 rigid, glabrous, al>out 

 1 cm. in diameter at the 

 base; nodes smooth; 

 sheaths striate, the 

 lower ones numerous, 

 imbricate, sparingly 



pubescent, the upper 

 scabrous ; ligule a dense 

 ciliate fringe of soft 

 liairs aljout 2 mm. long; 

 leaf-blades involute or 

 folded below, plane 

 aljove, 4 to 7 dm. long, 

 5 to 10 mm. wide, 

 glabrous beneath, sca- 

 brous on the upper sur- 

 face and margins, some- 

 what bearded at the 

 throat. Panicle very 

 lax, the lower portion 

 somewhat inclosed by 

 the upper sheath; rachis 

 smooth; branches alter- 

 nate, the lower ones in 

 clusters of twos at each 

 node, solitary above, 

 somewhat pubescent at 

 the axils, very slender, 

 the lower ones 2 dm. 

 long, simple or once 

 branched above the 

 middle. Spikelets 

 short-pedicellate, in 

 clusters of threes at the 

 end of the branches, 1.5 

 to 2 cm. long; empty glumes purple, 3-nerved, acute, the first slightly shorter 

 than the second, strongly scabrous on the keel and lateral nerves, slightly 

 scabrous on the margins; third glume nearly equaling and inclosed by the first 

 glume, 5-nerved, subtending a hyaline palea nearly its own length and a stami- 

 nate flower, flowering glume 8 to 9 mm. long, 9-nerved, pubescent throughout 

 with spreading white hairs, apex cleft, forming 2 acute teeth about 2 mm. long 

 and bearing between them a scabrous, geniculate awn 2 to 2.5 cm. in length, 

 which is twisted below the geniculation, straight above. 



Fig. 7 



-Tristachya la.ra Scribn. & Merrill: a. a grmip of spikelets; 

 6,' a single floret. 



