| General Information |
|---|
|
| Distribution | A taxonomically difficult genus of about 340 species. The largest numbers are native to the Americas, Africa, and Polynesia, with a few in Europe and Asia. Several weedy species have become naturalized worldwide.
|
|
|
|
Habit
|
Annual or perennial herbs or shrubs, 0.1‒4 m tall.
|
Leaves
|
Leaves simple and serrate or pinnately to tripinnately compound, opposite, pubescent or glabrous, petiolate.
|
Flowers
|
Heads solitary on long peduncle or in simple to compound cymes terminating the main stem and lateral branches or only on lateral branches, radiate or discoid; involucral bracts in 2 series, outer ones green and herbaceous, inner ones membranous or chaffy, rarely green and connate; receptacle chaffy; bracts usually linear, flat or nearly so; ray florets absent or 3‒19 per head, sterile, rays yellow or white, rarely orange or red; disk florets perfect or pistillate (and then plants gynodioecious), corollas yellow or orange, (4)5-lobed; tubular or urceolate nectary present, surrounding base of style; anthers sagittate with small, smooth auricles or entire; style branches tipped with short, acute or longer subulate appendages; pappus of 0‒4(‒8) barbed or glabrous awns.
|
Fruit
|
Achenes obovate-oblong, cuneate, or linear, obcompressed or 3‒4-angled, straight, curved, twisted, or coiled, occasionally with lateral wings, setose or glabrous.
|
|
|
|
|
|
|
|
|
|
|
|
|
Notes
|
See Wagner et al. (2014) for a revision of the endemic Marquesas Bidens. The name is derived from the Latin bi, two, and dens, teeth, in refrence to the usually paired pappus awns.
|
Contributor
|
Nancy Khan
|
