CAEDUACEAE. 



401 



the tube short, the limb 5-lobed. Anthers entire, or minutely 2-toothecl 

 at the base. Style-branches tipped with hirsute appendages. Achenes thick, 

 oblong or obovate, compressed, or somewhat 4-angled. Pappus of 2 scales or 

 awns, or sometimes with 2-4 additional shorter ones, deciduous. [Greek, pun- 

 flower.] About 60 species, natives of the New World. Type species: Heli- 

 anthus annuus L. 



1. Helianthus debilis Nutt. Low 

 Sunflower. (Fig. 441.) Annual, sca- 

 brous, branched, l°-3° high, the branches 

 mostly spreading or decumbent. Leaves 

 alternate, or the lower opposite, slender- 

 petioled, triangular-ovate to hastate, 11'- 

 3V long, acute or acuminate at the apex, 

 broadly cuneate to subcordate at the base, 

 repand-dentate or coarsely toothed; 

 heads about 2' broad, long-peduncled; 

 bracts of the involucre linear-lanceolate, 

 i' long or less, acuminate; rays 8-15, 

 bright yellow; disk purple, 7"-10" broad; 

 receptacle nearly flat. 



In a field, Middle Road, 1913, collected 

 by F. S. Collins. Introduced. Native of 

 the southeastern United States^ Flowers 

 in summer. 



Helianthus annuus L., Sunflov^^er, North American, a tall broad-leaved 

 annual herb, with rough stems and foliage, large heads at the ends of branches, 

 the disk-flowers purplish, the bright yellow rays often 6' long, is often grown 

 in gardens for ornament. 



Helianthus tuberosus L., Jerusalem Artichoke, North American, a tall 

 perennial, with rough ovate leaves, the rootstocks bearing edible tubers, the 

 heads '2'-3' broad, both disk-flowers and rays yellow, is occasionally grown in 

 gardens. 



16. BIDENS [Tourn.] L. 



Annual or perennial herbs, with opposite serrate lobed divided or dis- 

 sected leaves, or the uppermost alternate, and mostly large heads of both 

 tubular and radiate flowers, or the rays none, or rudimentary. Involucre cam- 

 panulate or hemispheric, its bracts in 2 series, distinct or slightly united at the 

 base; the outer often foliaceous. Receptacle flat or nearly so, chaffy, the chaff 

 subtending the disk-flowers. Rays, when present, neutral. Disk-flowers per- 

 fect, fertile, their corollas tubular, 5-toothed. Anthers entire, or minutely 

 sagittate at the base. Style-branches with short or subulate tips. Achenes flat, 

 quadrangular or nearly terete, cuneate, oblong, or linear. Pappus of 2-6 teeth 

 or subulate awns, upwardly or downwardly barbed or hispid. [Latin, two- 

 toothed, referring to the achenes.] About 75 species of wide geographic dis- 

 tribution. Type species: Bidens hipartita L. 



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