15.
Bidens aristosa
(Michaux) Britton, Bull Torrey Bot. Club. 20: 281. 1893.
Coreopsis aristosa
Michaux, Fl. Bor.-Amer. 2: 140. 1803;
Bidens aristosa
var.
fritcheyi
Fernald;
B. aristosa
var.
mutica
(A. Gray) Gattinger ex Fernald
Annuals,
(15—)30—60(—150) cm.
Leaves:
petioles 10—30 mm; blades lanceolate to lance-linear overall, 30—80(—150) × 10—30(—50) mm, usually laciniately pinnatisect, primary lobes 3—7+, 15—60+ × 2—20 mm, bases cuneate, ultimate margins laciniate to serrate, ciliate, apices acuminate, faces glabrous or sparsely scabrellous.
Heads
in ± corymbiform arrays.
Peduncles
(10—)30—80+ mm.
Calyculi
of 8—12(—16) usually spreading to reflexed, linear, seldom foliaceous bractlets (4—)5—7(—12) mm, margins entire, ciliate, abaxial faces glabrous or ± scabrellous.
Involucres
± hemispheric or broader, 6—8(—12) × 10—15 mm.
Phyllaries
7—8(—13), lance-ovate to lance-linear, 6—8(—12) mm.
Ray florets
(5—)8—10+; laminae yellow, 10—25 mm.
Disc florets
(12—)20—40+; corollas yellowish, 2—3+ mm.
Cypselae
red-brown to blackish, ± flattened (unequally 3—4-angled), broadly cuneate, outer (4—)5—6 mm, inner 5—7 mm (lengths mostly 1.5—2.5 times widths), margins (± corky-winged) patently to antrorsely barbed, apices truncate to concave, faces weakly striate, sometimes tuberculate, glabrous or sparsely strigillose;
pappi
0, or of 2(—4) spreading to divergent, antrorsely or retrorsely barbed awns (0.5—)2—4(—6) mm.
Flowering Aug—Oct(—Nov). Marshes, meadows, pine forests, disturbed sites; 0—300 m; Ont.; Ala., Ark., D.C., Ill., Ind., Ky., La., Md., Mich., Minn., Mo., N.C., S.C., Tenn., Tex., Va.
