1.
Bidens beckii
Torrey ex Sprengel, Neue Entd. 2: 135. 1821.
Bident de Beck
Megalodonta beckii
(Torrey ex Sprengel) Greene
Perennials
(perhaps flowering first year) to 200+ cm (aquatics).
Leaves
sessile; submersed blades multifid (2—3+-pinnatisect), ultimate lobes filiform, mostly 0.1—0.3 mm diam.; aerial blades ovate to lanceolate, 10—45+ × 5—20+ mm, bases cuneate, margins pectinately incised to serrate or entire, not ciliate, apices obtuse to acuminate or attenuate, faces glabrous.
Heads
usually borne singly.
Peduncles
(10—)20—100 mm.
Calyculi
of 5—6 usually spreading, oblong to obovate bractlets 5—8 mm, margins entire, not ciliate, abaxial faces usually glabrous.
Involucres
± hemispheric, 7—12 × 12—15 mm.
Phyllaries
7—8+, ovate, 7—10 mm.
Ray florets
8; laminae yellow, 10—15 mm.
Disc florets
10—30+; corollas pale yellow, 5—6 mm.
Cypselae
(outer and inner ± alike) yellowish to greenish brown, nearly terete or weakly 4-angled, ± linear, 10—15 mm, margins not barbed or ciliate, apices truncate, faces smooth or ± striate, glabrous;
pappi
of 2(—6) divergent to patent, retrorsely barbed (on distal
1
/4 or so) awns 13—25(—40) mm.
2
n
= 26.
Flowering Jul—Sep. Still or slow-moving waters; 0—300+ m; B.C., Man., N.B., N.S., Ont., Que., Sask.; Conn., Idaho, Ill., Ind., Iowa, Maine, Mass., Mich., Minn., Mo., Mont., N.H., N.J., N.Y., Ohio, Oreg., Pa., R.I., Vt., Wash., Wis.
M. L. Roberts (1985) presented a strong case for treating
Bidens beckii
as
Megalodonta beckii
.
SELECTED REFERENCE
Roberts, M. L. 1985. The cytology, biology and systematics of
Megalodonta beckii
(Compositae). Aquat. Bot. 21: 99—110.
