Ge.vvs 95.] 



THISTLE FAMILY. 



22. Senecio viscosus L. Fetid or Viscous 

 Groundsel. (Fig. 4054.) 



Senecio viscosus L. Sp. PI. S6S. 1753. 



Annual, viscid-pubescent, strong-scented; stem usually 

 much branched, i°-2° high. Leaves 1-2-pinnatifid, 1%'- 

 3' long, oblong or somewhat spatulate in outline, the seg- 

 ments oblong or cuneate, dentate or incised; lower leaves 

 petioled; heads few in the corymbs, 3"-4" broad, mostly 

 slender-peduncled; involucre nearly cylindric, 4"-5" 

 high, its bracts linear, acute, usuallj* with 1-3 shorter 

 outer ones; ra)s commonlj' about 20, very short, recurved 

 and inconspicuous; achenes glabrous; pappus bright 

 white, about one-third longer than the involucre. 



In waste places and on balla.st near the coast, New Bruns- 

 wick to North Carolina. July-Sept. 



96. ARCTIUM L. Sp. PI. S16. 1753. 



Large coarse branching, rough or canescent, mostly biennial herbs, with broad alternate 

 petioled leaves, and rather large heads of purple or white perfect tubular flowers, racemose, 

 corymbose or paniculate at the ends of the branches. Involucre subglobose, its bracts rigid, 

 lanceolate, tipped with spreading or erect hooked bristles, imbricated in many series. Recep- 

 tacle flat, densely bristly. Corollas tubular with 5-cleft limbs. Filaments glabrous. Anthers 

 sagittate at the base. Achenes oblong, somewhat compressed and 3-angled, ribbed, truncate. 

 Pappus of numerous short serrulate scales. [Greek, bear, from the rough involucre.] 



.•^bout 6 species, natives of Europe and .A.sia. 

 Bracts densely cottony; heads corymbose. i. A. tomentosum. 



Bracts of the involucre glabrous, or slightlj' woolly. 



Involucre i' broad or more; inner bracts equalling or e.^ceeding the flowers. 2. A. Lappa. 



Involucre 6"-9" broad; inner bracts not exceeding the flowers. 3. A. minus. 



I. Arctium tomentdsum (Lam.) Schk. 

 Woolly or Cottony Burdock. (Fig. 4055.) 



Lappa lomentosa Lam. Encj-cl. i: 377. 1783. 

 Arctiiini lomenlosiim Schk. Bot. Handb. 3: 49. 1803. 

 Arctium Lappa var. tomenlosnm A. Gray, Syn. Fl. i: 

 Part 2, 397. 1884. 



Similar to the following species. Heads 8"- 

 10" broad, corymbose at the ends of the branches, 

 mostly long-peduncled; bracts of the involucre 

 densely cottony, the inner ones erect and somewhat 

 shorter than the flowers. 



In waste places. New Brunswick to Massachusetts 

 and southern New York. ,\dventive from Europe. 

 ]uly-Aug. 



2. Arctium Lappa L. Great Bur, Burdock, 

 or Clotbur. (Fig. 4056. ) ^,._ ; ^ 



Arctium Lappa L. Sp. PI. 8i6. 1753. 



Lappa wo/'cr Gaertn. Fruct. & Sem. 2: 379. pi. 162. 1802. 



Stem much branched, 4°-9^ high. Leaves thin, 

 broadly ovate, pale and tomentosecanescent beneath, 

 obtuse, entire, repand or dentate, mostly cordate, the 

 lower often 18' long; petioles solid, deeply furrowed ; 

 heads clustered or subcorjmbose, sometimes long-pe- 

 duncled, l'-il4' broad; bracts of the involucre gla- 

 brous or nearly so, their spines all spreading, the inner 

 ones equalling or exceeding the flowers; corolla-tube 

 longer than the limb. 



