1030 FLORA. 



imbricated in many series. Receptacle flat, densely bristly. Corollas tubular with 

 5-cleft limbs. Filaments glabrous. Anthers sagittate at the base. Achenes ob- 

 long, somewhat compressed and 3-angled, ribbed, truncate. Pappus of numerous 

 short serrulate scales. [Greek, bear, from the rough involucre.] About 6 species, 

 natives of Europe and Asia. 



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



Bracts of the involucre glabrous, or slightly woolly. 



Involucre 25 mm. broad or more; inner bracts equalling or exceeding the flowers. 



2. A. Lappa. 

 Involucre 12-20 mm. broad ; inner bracts not exceeding the flowers. 



3. A. minus. 



1. Arctium tomentosum (Lam.) Schk. WOOLLY OR COTTONY BURDOCK. 

 (I. F. f. 4055.) Similar to the following species. Heads 16-20 mm. broad, corym- 

 bose 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, N. B. to Mass, and southern N. Y. Adventive from Europe. July- 

 Aug. 



2. Arctium Lappa L. GREAT BUR, BURDOCK, OR CLOTBUR. (I. F. f. 4056.) 

 Stem much branched, 12-27 dm. high. Leaves thin, broadly ovate, pale and 

 tomentose-canescent beneath, obtuse, entire, repand or dentate, mostly cordate, 

 the lower often 4.5 dm. long; petioles solid, deeply furrowed; heads clustered or 

 subcorymbose, sometimes long-peduncled, 3-4 cm. broad; bracts of the involucre 

 glabrous or nearly so, their spines all spreading; corolla-tube longer than the limb. 

 In waste places, N. B. and Ont. to southern N. Y., and locally in the interior. 

 Nat. from Europe. July-Oct. 



3. Arctium minus Schk. COMMON BURDOCK. (I. F. f. 4057 ) Smaller 

 than the preceding species, seldom over 15 dm. high. Leaves similar, the lower 

 deeply cordate; petioles hollow, not deeply furrowed; heads numerous, racemose 

 on the branches, short-peduncled or sessile; bracts of the involucre glabrous or 

 slightly cottony, the spines of the outer ones spreading, those of the inner erect and 

 shorter than the flowers; corolla-tube about as long as the limb. In waste places, 

 common throughout our area. Nat. from Europe. July-Nov. 



98. CARDUUS L. 



Erect, branched or simple, prickly herbs, some species acaulescent, with alter- 

 nate or basal, sinuate-dentate lobed or pinnatifid, usually very spiny leaves, some- 

 times decurrent, and large many-flowered, solitary or clustered, discoid heads of 

 purple, yellow or white, tubular, perfect and fertile, or rarely dioecious flowers. 

 Involucre ovoid or globose, its bracts prickle-tipped or unarmed, imbricated in 

 many series. Receptacle flat or convex, bristly. Corolla tube slender, the limb 

 deeply 5-cleft. Filaments pilose, or rarely glabrous. Anthers sagittate at the 

 base. Style-branches short or elongated, obtuse. Achenes obovate or oblong, 

 compressed or obtusely 4-angled, glabrous, smooth or ribbed. Pappus of several 

 series of slender, plumose, minutely serrulate, or simple bristles, connate at the 

 base. [The ancient Latin name of these plants.] About 250 species, widely dis- 

 tributed in the northern hemisphere. Besides the following, some 35 others occur 

 in the southern and western parts of N. Am. 



* Pappus-bristles, at least those of the inner flowers, plumose. (Plumed Thistles.) 

 t Outer involucral bracts, or all of them, strongly prickly-pointed. 



i. Leaves glabrous or hispid above, tomentose beneath (tomentose on 



both sides in No. 3). 

 All the bracts of the involucre tipped with prickles ; naturalized weed. 



i. C. lanceolatus. 



Outer bracts prickle-tipped, the inner merely acuminate; native species. 

 Branches leafy up to the heads ; involucral bracts firm or rigid. 



Leaves undivided, lobed or dentate, rarely pinnatifid. 2. C. altissimus. 



Leaves deeply pinnatifid into lanceolate or 'linear segments. 



Leaves tomentose on both sides, strongly spiny ; stem white-tomentose. 



3. C. Flodmanii. 

 Leaves glabrate above, weakly spiny; stem green, glabrous. 



4. C. discolor. 

 Heads naked-peduncled, 25 mm. high; involucral bracts thin. 5. C. Virginianus, 



