286 CAEDUACEAE. 



Tribe VIII. SENECIONEAE. 



Leaves opposite, sometimes mainly basal : pappus-bristles rigid. 43. Arnica. 

 Leaves alternate : pappus-bristles soft. 



Corollas white or pink : ray-flowers wanting. 



Heads with various flowers, the marginal pistillate, 



those of the disk perfect. 44. Erechtites. 



Heads with all flowers perfect. 



Involucre of about 5 main bracts. 45. Mesadenia. 



Involucre of 12-15 main bracts. 46. Stnosma. 



Corollas yellow : ray-flowers usually present. 47. Sbnecio. 



Tribe IX. CYNAREAE. 



Achenes inserted on the receptacle by their bases, not 

 oblique. 

 Receptacle not honeycombed, bristly. 



Achenes pubescent, without a rim at the top. 48. Xeranthemum. 



Achenes glabrous, with a rim at the top. 



Bracts of the involucre with hooked tips : leaves 



with unarmed blades, not bristly. 49. Arctium. 



Bracts of the involucre not hooked : leaves spine- 

 armed and often bristly. 

 Pappus-bristles plumose. 50. Cirsium. 



Pappus-bristles not plumose. 51. Cardods. 



Receptacle deeply honeycombed, not bristly. 52. Onopordon. 



Achenes obliquely inserted on the receptacle. 53. Centaurea. 



1. VEKNONIA Sehreb. Perennial caulescent herbs. Leaves alternate: 

 blades mostly toothed, often narrow. Heads not involucrate. Corolla-lobes 

 lanceolate. Anther-appendages lanceolate to oblong. Pappus double, the outer 

 series of scales or stout bristles, the inner of numerous capillary bristles. 



1. V. noveboracensis (L.) Willd. Stems 1-3 m. tall: leaf -blades linear- 

 lanceolate to elliptic-lanceolate, 8-20 cm. long, finely serrate or nearly entire: 

 involucres hemispheric, about 6 mm. high; bracts ovate to ovate-lanceolate, 

 with filiform tips arising abruptly from the body^ which in the inner bracts 

 about equal the tip in length: corolla about 10 mm. long: achenes 4-4.5 mm. 

 long. — Common, in low grounds and thickets. — Sum. — Iron-weed. 



2. ELEPHANTOPUS [Yaill.] L. Perennial scapose or caulescent herbs. 

 Leaves alternate: blades shallowly toothed. Heads involucrate. Corolla-lobea 

 linear-lanceolate. Anther-appendages deltoid to ovate. Pappus single, of 

 several rigid bristles terminating scale-like bases. 



1. E. carolinianus Willd. Stems 3-9 dm. tall, rather hirsute: leaf -blades 

 oblong, elliptic, or oval, 5-15 cm. long, crenate-serrate or repand: inner bracts 

 of the involucre 8-10 mm. long, acute: achenes 3.5-4 mm. long. — Lower 

 Susquehanna valley and adjacent parts. Frequent, in thickets. — Schists. — 

 Sum. — ■ Elephant 's-foot. 



3. EUPATORIUM [Tourn.] L. Perennial or rarely annual herbs, or 

 shrubs. Leaves alternate or opposite: blades entire^ toothed, or dissected. 

 Heads borne in corymbs. Involucres campanulate to cylindric. Corolla-lobea 

 ovate or triangular. Anther-appendages ovate. Aehene angled. Pappus of 

 capillary bristles. — Sum. — Thoroughwort. 



Leaves opposite or alternate, or rarely in 3's in 1 or 2 narrow-leaved species. 

 Leaf-blades manifestly petioled. 



Leaf -blades acuminate : corollas less than 3.5 mm. long. 



1. E. nrticaefolium. 

 Leaf-blades obtuse or abruptly acute : corollas over 



4 mm. long. 2. E. aromaticum. 



Leaf-blades sessile or essentially so, or connate-per- 

 foliate : heads less than 9-flowered. 

 Leaf-blades neither connate-perfoliate nor connate- 

 clasping. 



