This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
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 juncea Pursh. Heads solitary at the ends of the branches; leaves linear or subulate.
1. L. juncea.
Heads racemose along the branches; leaves elongated-linear.
2. L. rostrata.
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, 1/2'-2' long, 1/2"-1 1/2" wide, the upper similar but smaller, or reduced to subulate scales; heads 6"-8" broad, mostly 5-flowered, solitary 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, 21/2"-31/2" long; pappus light brown.
Plains, Minnesota to Saskatchewan, Montana, Wisconsin. Missouri, Nebraska, Kansas and Arizona. Often infested by a globose gall 2"-5" in diameter. June-Aug.
Lygodesmia rostrata A. Gray, Proc. Am. Acad. 9: 217. 1874.
Annual, less rigid; stem striate, leafy, paniculately branched, 1°-3° high. Leaves elongated-linear, acuminate, entire, 3-nerved, the lower 3'-7' long, 1"-1 1/2" wide, the uppermost very small and subulate; heads numerous, 7-10-flowered, about i' broad, racemose along the branches on scaly short erect peduncles; involucre 5"-7" high; achenes narrowly fusiform, narrowed or somewhat beaked at the summit, 5-8-ribbed or -striate, 4"-5" long, longer than the whitish pappus.
Plains and canyons, South Dakota to Saskatchewan, Nebraska, Kansas, Colorado and Wyoming. Aug.-Sept.