THISTLE FAMILY 935 



beneath, 3-7 cm. long; heads few, paniculate; involucres scarcely 1 cm. high, 

 1.5 cm. broad; ligules orange, 12-15 mm. long. Verbesina encelioides exauriculata 

 Robins. & Greenm. Mountain valleys: Mont. Tex. Ariz. Son. Mont. Je-O. 



78. COREOPSIS L. TICKSEED. 



Annual or perennial herbs. Leaves various. Heads on long peduncles, 

 radiate. Involucres campanulate, their bracts in two series, all more or less 

 united at the base, the outer ones usually narrow and foliaceous, the inner broad, 

 variously colored, in ours orange or brown, scarious or with scarious margins. 

 Ray-flowers neutral; ligules yellow. Disk-flowers fertile. Receptacle flat or 

 slightly convex. Achenes flat or more or less convex on the back. Pappus of 

 two fimbriate squamellae, two awns or minute teeth, or none. 



Leaves pinnatifld. 



Acfienes winged. 1. C. Atkinsoniana. 



Achenes wingless. 2. C. tinctoria. 



Leaves simple. 3. C. lanceolata. 



1. C. Atkinsoniana Dougl. Annual or perennial (?), with a taproot; stem 

 4-10 dm. high, glabrous; leaves opposite, pinnately or bipinnately divided into 

 linear divisions, glabrous; involucres about 6 mm. high, 15 mm. broad; outer 

 bracts oblong, obtuse, the inner broadly ovate; ligules orange, 12-15 mm. long. 

 River banks: B.C. N.D. Ore. Plain. Jl-Au. 



2. C. tinctoria Nutt. Annual, with a taproot; stem 4-10 dm. high, glabrous; 

 lower leaves bipinnately, the upper ones pinnately divided into linear divisions, 

 glabrous; involucres about 7 mm. high, 10-15 mm. wide; outer bracts oblong, 

 in fruit reflexed; inner bracts ovate or lance-ovate, acute; ligules 8-12 mm. long, 

 orange, with or without purple base. Low ground: Man. Va. Tex. Ariz. 

 e B.C. Plain. Je-Au. 



3. C. lanceolata L. Perennial, with a short rootstock; stem 2-5 dm. high, 

 glabrous; leaves opposite, the lower spatulate or oblanceolate, petioled, the upper 

 linear-lanceolate or linear, obtuse; involucres 8 mm. high and 12-15 mm. broad; 

 outer bracts lanceolate, only slightly shorter than the ovate-lanceolate inner 

 ones; ligules orange, 12-25 mm. long, coarsely toothed; achenes broadly wing- 

 margined; pappus obsolete. Rich soil: Ont. Fla. La. N.M. Colo. Plain. 

 My-Au. 



79. BIDENS L. BEGGAR-TICKS, BUR-MARIGOLD. 



Caulescent herbs, ours all annual. Leaves mostly opposite, simple or pinna- 

 tifid. Heads numerous, radiate or discoid. Involucres campanulate or tur- 

 binate, of two series of bracts, distinct or united only at the very base, the outer 

 foliaceous, the inner scarious and appressed. Receptacle flat, chaffy. Ray- 

 flowers neutral; ligules yellow or white, or none. Disk-flowers hermaphrodite 

 and fertile. Achenes flat, 4-angled, or rarely almost terete, beakless. Pappus 

 of 1-A (in ours retrorsely) barbed awns or teeth, rarely none. 



Achenes flat, obovate or cuneate; leaves or segments broad. 

 Leaves pinnately 3-5-foliolate. 



Outer bracts 4-8; achenes nearly black. 1. B. frondosa. 



Outer bracts 10-16; achenes brown. 2. B. vulgata. 



Leaves simple. 



Heads discoid, erect; corolla 4-toothed; achenes not tubercled. 3. B. comosa. 

 Heads usually radiate, nodding; corolla 5-toothed. 



Outer bracts not much longer than the inner; achenes not corky on the angles. 



4. B. prionophylla. 

 Outer bracts surpassing the rays; achenes with corky angles. 



5. B. glaucescens. 

 Achenes linear, tetragonal; leaf-segments small. 



Divisions of the leaves oblong or lanceolate. 6. B. Bigelovii. 



Divisions of the leaves linear. 7. B. tenuisecta. 



1. B. frondosa L. Annual; stem 3-10 dm. high; leaves pinnately 3-5-folio- 

 late, glabrous or nearly so, scabrous on the margins; leaflets 3-8 cm. long, lanceo- 

 late or oblong-lanceolate, sharply serrate, acuminate; involucres 10-15 mm. 

 high and broad; outer bracts 4-8, spatulate-linear, entire, ciliate; ligules usually 



