ORDER LXVIII. — COMPOSITJE. 395 



Genus LIV.— BI'DENS. L. 



(From lidens, two teeth, from the two nwns of the fruit) 



Involucre double, tlie outer unequal ; ray florets neutral when 

 present, frequently wanting ; those of the disk perfect. Recep- 

 tacle flat, chaft'y ; pappus consisting of 4 retrorsely scabrous 

 awns. Seed quadrangular. 



1. B. chrysantuemoi'des, (MioJj.) Stem glabrous below, somewhat 

 pubescent toward the summit, with opposite branches. Leaves sessile, 

 opposite, oblong-lanceolate, serrate, ghibrous, somewhat connate ; invo- 

 lucre double, the exterior one consisting of about 8 unequal, foliaceous 

 leaves ; the interior of about the same number of equal, membranace- 

 ous leaves ; ray florets lanceolate, 8. Seed compressed, oblong ; pap- 

 pus consisting of 2 awns which are distinct, and 2 others very minute ; 

 receptacle convex. — Yellow. If. Oct, — Nov. In wet, cultivated 

 lands. 2—3 feet. 



2. B. conna'ta, (Muhl.) Stem glabrous, with opposite brandies. 

 Leaves opposite, lanceolate, toothed, glabrous, attenuate at the base ; 

 the lower ones ternute, the upper ones simple, all sessile. Flowers sol- 

 itary, on opposite peduncles; the exterior involucre foliaceous, the in- 

 terior chaffy; ray florets none. — Yellow. 2^. July — Oct. Middle 

 Car. and Geo. 2—3 feet. 



3. B. FRONDo'sA, (L.) Stem slightly pubescent, branching. Leaves 

 lanceolate ; the lower ones pinnate, the upper ternate and simple, 

 slightly pubescent. Flowers solitary, on opposite and terminal pedun- 

 cles ; exterior involucre with unequal, ciliate scales ; the exterior chaffy; 

 ray florets none. — Yellow. U- June— Sept. Damp soils. Common. 



4. B. bipinna'ta, (L.) Stem glabrous, obtusely angled, with opposite 

 branches. Leaves opposite, decussate, bipinnate ; leaflets lanceolate, 

 pinnatifid, slightly pubescent along the margin. Flowers on long, usu- 

 ally terminal, peduncles ; exterior involucre with linear-lanceolate 

 leaves ; interior leaves ciliate toward the summit. Seed slightly angled. 

 — Yellow. If. July — Oct. Common. 2—4 feet. 



Genus LV.— ACMEL'LA. L. {Spilanlhes, Jacq.) 

 (From akme, a point.) 



Involucre consisting of 12 leaves, arranged in a double series, 

 pubescent, equal ; florets of the ray pistillate, of the disk per- 

 fect. Seed quadrangular, compressed. Receptacle cliafty, with 

 yellow scales. 



1. A. re'pens, (Pers.) Stem procumbent, rooting at the lower joints, 

 pubescent. Leaves opposite, ovate-lanceolate, attenuate at the base, 

 slightly pubescent. Flowers solitary, on axillary and terminal pedun- 

 cles. Leaves of the involucre ovate-lanceolate, acute ; ray florets about 

 12. /S^erf oblong, naked, truncate at the summit. — Yellow. If. Sept 

 —Oct. Wet soils. 1—2 feet. 



2. A. NuTTALL'n, (T. & G.) Stem pubescent, diffusely branched. 

 Leaves ovate or oblong-ovate, coarsely serrate. Achcnia with ciliato 

 margins. — Lou. 



