46 



July 2, 1897) ; near Jeffersou City, Mont. (No. 340, F. Lamsou-Scribuer, June 27, 

 1883). Named for Thomas A. Williams, assistant agrostolojiist. 

 This species has been confounded with Stipa riridiila, from which it is readily dis- 

 tinguished by its longer and more acute callus and pubescent culms and sheaths. 

 It is more nearly allied to iilipa virhJiiht var. puhescenti ^^asey, from Washington State, 

 which i)os8esses the same character of pubescence. In that species, however, the 

 awns are pubescent to the second bend. Slipa viridulu var. pitbesccns Vasey is eciually 

 distinct from S. riridtila and may be classed as a distinct siiecies and named S. elmeri 

 I'iper & Brodie, under which name it has recently been distributed by Mr. Elmer. 

 There is a Siqxi iiKhcaccns R. Br. 



STIPA NELSONI 8cribn., sp. n. 



A rather stout, glabrous, ca-spitose perennial, 7 to 9 dm. high, with long, narrow 

 culm leaves, and strict panicles 15 to ^5 cm. long. Culms smooth; sheaths stri- 

 ate, smooth, the overlapping margins pilose with soft hairs. Ligule very short 

 (less than 1 mm.), n-ud minutely fringed on the edge, slightly auricled and pubes- 

 cent on the sides. Panicle branches appressed, 4 to 5 cm. long, all excepting the 

 longer ones liower-bearing to the base; lowermost branches sometimes 10 cm. 

 long. Enqity glumes slightly unequal, the first to 10 ram. long, 3-nerved, the 

 second a little longer and narrower, 5-nerved near the base, both glumes long 

 acuminate-pointed, very thin and hyaline excepting the nerves, which are quite 

 conspicuous. Flowering glumes, including the rather acute callus, 7 mm. long, 

 clothed with soft, silky hairs, which are longest at the shortly two-toothed apex. 

 Palea rather broad, half as long as the glume, jjilose on the back, truncate at 

 the apex or irregularly toothed. Awn about 3.5 cm. long, minutely scabrouB. 

 Anthers beardless. 



Woods Landing, Albany County, Wyo., altitude 2,{>00 meters (No. 3963, A. Nelson, 

 August 9, 1897); rich soil. Sheep Mountain, "common and attords consider- 

 able forage," altitude 2,400 meters (No. 2269, Thomas A. Williams, July 2, 1897.) 

 Named for Prof. Aven Nelson. 



This grass has been confounded with Stipa viridula, from which it is readily distin- 

 guished b)' its longer and more pointed callus to the flowering glume, and espe- 

 cially by tlie silvery, comose appearance of the iianicle. Tlie silvery appearance 

 is duo to the hyaline character of the outer glumes. The details of the spike- 

 lets arc more nearly those of Stipa vaseyi Scribn., new name (Siipxt viridula 

 robusta Vasey, not S. rohusta Nutt.), but in that species the outer glumes are 

 quite iirm in texture, and minutely but distinctly scabrous all over the back. 

 In this species the glumes are perfectly smooth on the back, and the awns are 

 more than twice as long as in Stipa raseyi. 



STIPA MINOR (Vasey) Scribn. {S. riridula var. minor Vasey Contr. V. S. National 

 Herbarium 3 : page 50.) 



A densely c,isi)itose, erect, glabrous perennial, 4 to 6 dm. high, with narrow leaves 

 and densely flowered, usually ])uri)lish ]>anicles5 to 12 cm. long. Culms smooth 

 or very minutely pubescent below the nodes. Sheaths smooth. Ligule very 

 short, slightlj^ auricled, broader than the base of the leaf-blade. Leaf-blade 

 10 to 30 cm. long, 2 to 3 mm. wide, with very long attenuate-involute tips, scab- 

 rous on the margins, otlierwisc smooth. Leaves of the innovations involute and 

 ahnost filiform, at least when dry. Spikelets 6 to 7 mm. long. Hnijjty glumes 

 lanceolate, sharply acuminate-pointed, 3-nerved near the base, the first slightly 

 broader and longer than the second and less distinctly nerved. Flowering glume, 

 including the short callus, iibout 4 mm. long, thinly i)iloseall over with a crown 

 of hairs at the distinctly 2-toothod apex. Palea about three-fourths as long as 

 the glume. Awn once or twice geniculate, about 18 mm. long, very minutely 

 scabrous. 



