Bidens.
In Family Asteraceae the Bidens genus has 222 species.
Most are native to Mexico and Africa but they are found worldwide.
They are annual or perennial herbs or shrubs with opposite leaves on petioles.
The blades can be entire or divided into 3 to 9 narrow or wide lobes.
The terminal inflorescences are a single head (capitulum) or a branched cluster.
There are 2 whorls of bracts or phyllaries in the involucre.
The outer green ones have 1 to 3 veins.
Coloured bracts in the inner whorl have a thin membranous edge.
The receptacle is flat to conical and has pale oblong membranous scales or paleae.
The neuter or female ray florets have a white, yellow or orange ligule.
The bisexual yellow or brown disk florets have a tubular base with 5 small lobes.
The 5 loosely fused brown anthers have an apical and basal appendage.
The ovary has a single style with 2 branches holding the linear stigmas.
The fruit are cypselae (loosely called achenes which come from a superior ovary.)
They can be flat, angled, ribbed or with narrow wings and there may be hairs.
The pappus is 2 to 4 bristles with downward pointing barbs.
J.F.
