RAGWEED FAMILY 831 



Leaves pinnately 3-5-parted or entire; divisions or blades merely serrulate or 

 entire. 7. jp. tomentosa. 



Fruit villous; plant shrubby. 8. F. eriocentra. 



1. F. albicaulis Torr. Low shrub, often spinescent, divaricately branched, 

 with white bark, 3-10 dm. high; leaves pinnate or bipinnate, silvery white; seg- 

 ments small, obovate, usually toothed ; spike sohtary ; pistillate heads often mixed 

 with the staminate ones, the latter about 4 mm. broad; involucres canescent, 

 lobed to the middle; fruit about 8 mm. long; spines flattened, subulate, spreading 

 or recurved in age. Desert regions: s Utah — Nev. — Calif. — Ariz.; n Mex. L. 

 Son. Mr-My. 



2. F. acanthocarpa (Hook.) CoviUe. Annual;stemerect, diffusely branched, 

 3-6 dm. liigh, hirsute or hispid, with white hairs; leaves petioled or the upper 

 sessile, bi- or tri-pinnatifid; divisions or their lobes oblong, elliptic or linear, 

 hispid-strigose on both sides or glabrate above; staminate heads nodding, about 

 3 mm. broad; involucres dark brown with 3 blackish ribs, cleft beyond the middle 

 into 6-7 oval lobes; fertile heads 1-flowered; fruit 12-20 mm. long, with 7-12 

 flattened lance-subulate divergent spines. F. Hookeriana Nutt. Gaertneria 

 acanthocarpa Britton. Plains and sandy valleys: Sask. — Mo. — Tex. — Calif. — 

 B.C. Son.—Submont. Jl-0. 



3. F. montana Nutt. Annual; stem 3-6 dm. high, strigose or hispidulous, 

 angled, branched; leaves petioled, ovate in outUne, pinnate!}' 3-5-divided, his- 

 pidulous-strigose on both sides; divisions ovate or obovate, or the terminal one 

 rhombic, often 2-3-cleft and roxmd-lobed; staminate heads similar to those of 

 the preceding, but the involucres scarcely cleft to the middle; fruit similar but 

 1 cm. long or less, and spines more crowded. Sandy places: Utah — Ore. — se 

 Calif. Son. Au-0. 



4. F. tenuifolia Harv. & Gray. Perennial; stem 3-15 dm. high, pubescent 

 or nearly glabrous; leaves bi- or tri-pirmatifid into oblong or Unear divisions, 

 strigose; staminate heads about 4 mm. broad; involucre pilose, lobed to near the 

 middle; bur 1-2-flowered, but with a single beak, glandular-puberulent and 

 with a depression above each hooked spine. Valleys: Tex. — Colo. — s Calif.; 

 Mex. Son. My-N. 



6. F. linearis Rydb. Perennial, shrubby at base; stems about 2 dm. high, 

 sparingly hirsute, branched; leaves once or twice pinnate, 3-4 cm. long, strigose 

 above, minutely tomentulose beneath; lobes hnear, obtuse, 3-5 mm. long; stam- 

 inate heads nodding, 3-4 mm. wide; involucre strigose, cleft scarcely half-ways 

 into rounded-ovate lobes; pistillate involucre with few hooked slender spines. 

 G. linearis Rydb. Dry plains: Colo. Submont. Jl. 



6. F. discolor Nutt. Perennial with a rootstock; stem 2-4 dm. high, spar- 

 ingly pubescent; leaves petioled, interruptedly pinnatifid, strigose above, white- 

 tomentose beneath ; larger division oblanceolate, cleft and with triangular teeth; 

 staminate racemes usually soUtary; heads about 5 mm. wide; involucre finely 

 pubescent, with 5-8 short, lobes; pistillate heads 2-flowered; fruit ovoid, 4—5 mm. 

 long; spines short, with conic bases and usually sUghtly curved tips; beaks 2, 

 short, hooked at the apex. Gaertneria tomentosa (Nutt.) Heller. Dry soil: S.D. — 

 Kans. — Ariz. — Wyo. Plain— Submont. Jl-Au. 



7. F. tomentosa A. Gray. Perennial; stem 3-10 dm. high, strict, purpUsh, 

 somewhat tomentose or glabrate below; leaves pinnately 3-5-parted or entire, 

 white-tomentose on both sides or grayish above; blades or divisions lanceolate- 

 serrate; staminate racemes paniculate; heads about 4-5 mm. broad; involucre 

 tomentose, round-lobed; bur 6-8 mm. long, glandular-puberulent, 2-flowered, 

 2-beaked, with terete hooked spines. Gaertneria Grayi A. Nels. River bottoms: 

 Neb. — Kans.— Colo. Plain. Au-S. 



8. F. eriocentra A. Gray. Low shrub, with gray bark, minutely tomentose; 

 leaves 2-4 cm. long, oblanceolate or cuneate-oblong, soon glabrate above, white- 

 tomentulose beneath, coarsely sinuately toothed or lobed; staminate heads few, 

 in short, terminal racemes, 6-7 mm. broad; involucre canescent, with triangular 

 lobes; fruit about 1 cm. long, the beak equalling the body; spines slender, shghtly 



