The Flora of the Cayuga Lake Basin 417 



e. Outer involucral bracts exceeding the disk, unequal, spreading, folia- 

 ceous ; rays twice the length of the disk or less ; chaff not reddish- 

 tipped ; achenes slightly dilated at summit, 4-angled, usually warty ; 

 awns 4; stems erect. 

 /. Heads large, cernuous, the disks 15-25 mm. wide; outer bracts of the 

 involucre 7-8; inner bracts about 8, 7-10 mm. long. 

 g. Leaves broadly linear or linear-lanceolate, only slightly contracted 

 below the middle, usually connate, unevenly and distantly serrate; 

 plants 2-7 dm. high, sparingly branched. 3. B. ccrnua 



g. Leaves elliptic-lanceolate or elliptical, narrowed to a scarcely con- 

 nate base, more evenly and closely serrate; plants taller, 5-15 

 dm. high, much branched and generally with more showy heads. 



3a. B. c.,var. elliptica 

 f. Heads small, usually solitary, obscurely cernuous, the disks 1.5-10 mm. 

 wide; outer bracts of the involucre 2-^6; inner bracts 3-6, 2-7 mm. 

 long. 3b. B. c, var. minima 



e. Outer involucral bracts rarely exceeding the disk, nearly equal, seldom 

 conspicuously foliaceous, slightly fleshy; rays two to four times the 

 length of the disk; chaff reddish-tipped; achenes not dilated above, 

 flat, 1-nerved on the outer face, rarely warty; awns 2-4; heads 

 scarcely cernuous, more helianthoid than in the preceding species ; 

 stems decumbent, often floating at base. 4. B. laevis 



d. Leaves pinnately divided ; achenes flat ; awns 2, short, upwardly barbed ; 

 heads not cernuous. \B. trichosperma \ 



c. Rays scarcely exceeding the disk, or wanting (see also no. 3). 

 d. Leaves clearly pinnatifid or ternatifid; margins of the achenes upwardly 

 barbed, except rarely toward the top. 

 e. Outer involucral bracts 4-8 ; inner bracts oblong, equaling the disk ; 

 ray ovaries, when present, hairy, minutely awned ; disk achenes nar- 

 row, hairy, the margins warty, upwardly barbed to base of awns ; 

 corolla orange, goblet-shaped. 

 /. Leaf divisions 3, long-acuminate ; achenes 4-5.5 mm. long ; awns 



upwardly barbed ; outer involucral bracts 4. 5. B. discoidca 

 f. Leaf divisions 3-5, pinnately arranged, acute or short-acuminate ; 

 achenes 6 mm. long ; awns downwardly barbed ; outer involucral 

 bracts 6-8. 

 g. Branches of the plant widespread ; leaf divisions green, all dis- 

 tinct ; heads short-peduncled ; outer involucre only slightly longer 

 than the disk ; corollas 2.5-3 mm. long, orange, 5-toothed. 



6. B. frondosa 

 g. Branches strongly ascending ; leaf divisions pale, those of the 

 upper leaves confluent; heads long-peduncled ; outer involucre very 

 foliaceous, two to four times the length of the disk; corollas 3-4 

 mm. long, more nearly yellow, often 4-toothed ; achenes larger and 

 smoother. 6a. B. f., var. pallida 



e. Outer involucral bracts 10-16, more ciliate ; inner bracts ovate-triangular, 

 short ; ray ovaries, when present, glabrous, awnless ; disk achenes 

 broad and flat (one-half as broad as long), nearly smooth and gla- 

 brous, the uppermost fourth of the margin downwardly barbed; corolla 

 stramineous, funnel-form. 7. B. vulgata 



d. Leaves simple or irregularly lobed ; margins of the achenes downwardly 

 barbed, or with mixed ascending and reflexed barbs. 

 e. Corolla stramineous, funnel-form, 4-toothed ; stamens included ; achenes 

 broad, flat, 8-11 mm. long, «3-awned, the margins downwardly barbed; 

 outer involucre very foliaceous, much exceeding the disk. 



8. B. comosa 



