CAKDUACEAE. 305 



4-angled, embraced by the bractlets. Pappus of 2 awns or scales, sometimes 

 accompanied by smaller awns, all deciduous. Fall. SUNFLOWER. 



Leaf-blades petioled or with petiole-like bases. 

 Main stem smooth and glabrous. 



Bracts of the involucre much surpassing the top of the disk. 



1. H. decapetalus. 

 Bracts of the involucre about equalling the top of the 



disk. 2. H. strumosus. 



Main stem pubescent. 



Leaf-blades prevailingly ovate or ovate-lanceolate. 3. H. tuberosus. 



Leaf-blades prevailingly lanceolate. 



Leaves mostly alternate ; blades narrowed at the 



base : achenes narrow, cuneate-oblong. 4. H. giganteus. 



Leaves mostly opposite ; blades obtuse at the base : 



achenes broad, obovoid. 5. H. ambiguus. 



Leaf-blades sessile and partly clasping. 6. H. divaricatus. 



1. H. decapetalus L. Stems 5-16 dm. tall, glabrous below the inflorescence: 

 leaf-blades membranous, ovate to oblong-lanceolate, 8-20 cm. long, coarsely 

 serrate: bracts of the involucres linear to linear-lanceolate, 1.5-2 cm. long: 

 ligules of the ray 2.5-3 cm. long : disk about 1.5 cm. broad. Common, in 

 moist thickets and along streams. 



2. H. strumosus L. Stems 6-18 dm. tall, glabrous or nearly so to the in- 

 florescence: leaf-blades ovate to lanceolate or oblong-lanceolate, 8-20 cm. long, 

 whitish beneath: bracts of the involucre lanceolate to oblong-lanceolate, the 

 inner ones scarcely dilated: ligules of the ray 2.5-4 cm. long: disk 1.5-2 cm. 

 broad. Common, on dry banks and in thickets. 



3. H. tuberosus L. Stems 6-30 dm. tall, scabrous to hirsute: leaf -blades 

 ovate to lanceolate, 8-20 cm. long, shallowly or coarsely toothed: bracts of the 

 involucres linear to linear-lanceolate, the inner 12-21 mm. long: ligules of the 

 ray 2.5-4 cm. long: disk 15-20 mm. broad. Common, in rich soil, waste places 

 and fence-rows. 



4. H. giganteus L. Stems 9-30 cm. long, scabrous and hispidulous at least 

 above: leaf-blades lanceolate to oblong-lanceolate or linear-lanceolate, 5-15 

 cm. long, toothed or nearly entire : bracts of the involucre lanceolate or elliptic- 

 lanceolate, the inner 13-18 mm. long: ligules of the ray 1.5-2 cm. long: disk 

 10-15 mm. broad: achenes cuneate-oblong, 1.5-2 mm. wide. Common, in low 

 grounds. JERUSALEM-ARTICHOKE. 



5. H. ambiguus (T. & G.) Britton. Similar to H. giganteus in habit, but less 

 harshly pubescent : leaves mostly opposite ; blades lanceolate, rounded at the 

 base : bracts of the involucre attenuate, reflexed at maturity : achenes obovoid, 

 2.5-3 mm. wide. S. Bare, in thickets near Pleasant Grove. Schists. 



6. H. divaricatus L. Stems 3-12 dm. tall, commonly smooth and glabrous: 

 leaf -blades lanceolate or ovate-lanceolate, sessile or nearly so : bracts of the 

 involucre lanceolate or oblong-lanceolate, 8-10 mm. long: disk 10-15 mm. 

 broad. N. S. Frequent, in thickets. Sandstones and shales, schists. 



34. RIDAN Adans. Perennial rather coarse tall herbs. Leaves alter- 

 nate or opposite : blades usually toothed and decurrent. Heads several or 

 numerous. Involucre narrow: bracts few, spreading or recurving, becoming 

 lax. Bay-flowers few: ligules yellow or white, or wanting. Disk-corollas with 

 a funnelform throat rather abruptly contracted into the shorter tube: lobes 

 lanceolate. Filaments slightly shorter than the anthers. Pappus of 2 more or 

 less spreading awns, accompanied by 2 or 3 smaller awns, or scales. 



1. R. alternifolia (L.) Britton. Plants 6-25 dm. tall: leaf -blades oblong or 

 elliptic, 9-30 cm. long: disk-corollas 5 mm. long: achene-body with ciliate 

 wings. Common, in moist thickets and on roadsides. 

 Lancaster County Flora 20. 



