3 22 



CKHOKIACEAE. 



Vol. 111. 



18. LYGODESMIA 1). Don, Fdinb. Phil. J. mrn. 6: 311. 1829. 



Perennial or annual glabrous rigid branching herbs, with linear leaves, or the basal and 

 lower ones sometimes broader and pinnatifid, those of the stem very narrow and entire or 

 reduced to linear scales, and middle-sized 3-12-flowered heads of pink or purple flowers, 

 solitary and erect at the ends of the stem and branches, or sometimes racemose. Involucre 

 cylindric, its principal bracts 5-8, linear, scarious-margined, equal, slightly united at the base, 

 with several very short outer ones. Receptacle flat, naked. Rays truncate and 5-toothed at 

 the apex. Anthers sagittate at the base. Style-branches slender. Achenes linear, smooth 

 or striate. Pappus of copious somewhat unequal simple bristles. [Greek, twig-bundle, from 

 the numerous branches.] 



About 6 species, natives of western and southern North America. Type species: Prenanthes 

 junc e a Pursh. 



Heads solitary at the ends of the branches; leaves linear or subulate. i. L. juncea. 



Heads racemose along the branches; leaves elongated-linear. 2. L.rostrata. 



i. Lygodesmia juncea ( Pursh) D. 



Don. Rush-like Lygodesmia. 



Fig. 4079. 



Prenanthes juncea Pursh, Fl. Am. Sept. 498. 

 1814. 



Lygodesmia juncea D. Don; Hook. Fl. Bor. 

 Am. 1 : 295. 1833. 



Perennial by a thick woody root ; stems 

 stiff, striate, much branched. 8-18' high, 

 the branches erect. Lower leaves linear- 

 lanceolate, rigid, entire, acute or acuminate, 

 -2' long, I'-li" wide, the upper similar 

 but smaller, or reduced to subulate scales ; 

 heads 6"-8" broad, mostly 5-flowered, soli- 

 tary at the ends of the branches ; involucre 

 6"-8" high ; achenes narrowly columnar or 

 slightly tapering, truncate at the summit, 

 about 8-nerved or ribbed, 2h"-^i" long; 

 pappus light brown. 



Plains. Minnesota to Saskatchewan, Mon- 

 tana, Wisconsin, Missouri, Nebraska, Kansas 

 and Arizona. Often infested by a globose gall 

 2"-s" in diameter. June-Aug. 



2. Lygodesmia rostrata A. Gray. 

 Beaked Lygodesmia. Fig. 4080. 



/.. juncea var. rostrata A. Gray, Proc. Phil. 

 Acad. 1863: 69. 1863. 



Lygodesmia rostrata A. Gray, Proc. Am. Acad. 

 9; 217. 1874. 



Annual, less rigid;. stem striate, leafy, 

 paniculately branched, l-3 high. Leaves 

 elongated-linear, acuminate, entire. 3-nerved, 

 the lower 3'-7' long, i"-ii" wide, the upper- 

 most very small and subulate ; heads numer- 

 ous, 7-10-flowered, about broad, racemose 

 along the branches on scaly short erect pe- 

 duncles ; involucre S"-7" high ; achenes nar- 

 rowly fusiform, narrowed or somewhat 

 beaked at the summit, 5-8-ribbed or -striate, 

 4"-S" long, longer than the whitish pappus. 



Plains and canyons, South Dakota to Sas- 

 katchewan, Nebraska, Kansas, Colorado and 

 Wyoming. Aug.-Sept. 



