No. 15. 

 ELIONURUS BARBICULMIS Hackel. 



Rootstock not seen, apparently creeping. Roots rather thick, mostly simple, 

 nnbranched, with a thin brown bark. 



Culms densely tufted, erect, 1 to 3 feet high, slender, rigid, below the nodes 

 pilose, a little lower scabrous, and lower yet glabrous; many short, producing only 

 leaves. 



Leaves of the stem 3 to 5; sheaths slender, usually not contiguous, glabrous, 

 sparingly long-ciliate on the margins above; blade 8 inches long or less, the up- 

 permost often entirely wanting, about ■£ line wide, closely involute, long-pilose 

 on the margins below, densely hairy for a short distance from the liglue within, 

 otherwise glabrous, rising erect from the sheath; ligule a dense row of stiff hairs. 

 Root leaves and those of the abortive stems similar to the last, but reaching 1 foot 

 in length, tips frequently flexuous. 



Inflorescence a more or less pedunculate terminal distichous spike, 2 to 4 

 inches long, about 3 lines thick, densely villous on both the rachis. pedicels, and 

 spikelets; rachis flat. 



Spikelets inserted 2 together on one side of the rachis at each joint; one ses- 

 sile, 3 to 4 lines long; other pedicelled, of about the same length, including the 

 pedicel. 



Glumes 4; first lanceolate, several-nerved, densely villous on the back, apex bifid 

 into two slender points; second lanceolate, 3-nerved, more or less villous in the 

 middle of the back, these two inclosing the rest of the spikelet; third thin, mem- 

 branaceous, laterally 2-nerved, ciliate on the inflexed margins; fourth (flowering) 

 lanceolate, membranaceous, 1- to 3-nerved, glabrous. 



Flower of sessile spikelet hermaphrodite; palet lanceolate, minute, membra- 

 naceous; lodicules 2, about £ line long, thick; stamens 3, linear, anthers 1-J- to 2 

 lines long; stigmas long, cylindrical. Flower of pedicelled spikelet staminate; 

 palet wanting, lodicules as in the hermaphrodite flower; stamens 3, shorter than 

 the others. 



Grain light-brown, obcompressed, elliptical-lanceolate, acute at each end; em- 

 bryo occupying half its length. Rachis of the spike finally disarticulating just 

 below the nodes, bearing the 2 spikelets, one containing the grain. 



Plate XV; a, portion of the rachis of the spike, showing the two spikelets at 

 a node, opened to show their parts. The palet of the lower spikelets is not shown. 



This species occurs on rocky hills in western Texas, southern New Mexico, 

 and Arizona, and the adjacent parts of Mexico. 



