The genus of tiny flowering plants that includes the world’s smallest flower is Wolffia.
Wolffia is a genus of free-floating freshwater plants commonly called watermeal or rootless duckweed. The plants look like tiny green grains or specks of cornmeal on ponds, lakes, and marshes. They have no roots, stems, or conventional leaves; instead, each plant consists largely of a small floating body called a frond.
Their flowers are exceptionally easy to miss. A flower develops in a cavity on the upper surface of the frond and contains just one stamen and one pistil. Wolffia usually spreads vegetatively, with a parent frond producing daughter fronds, although the plants can also reproduce by seed.
The species Wolffia globosa is often identified as the smallest flowering plant, but the quiz asks for the genus, making Wolffia the canonical answer. The plants are more than botanical curiosities: some species grow rapidly, and Wolffia microscopica has recorded doubling times of about 29.3 hours. Wolffia has also been eaten as a vegetable in parts of Asia and studied as a high-protein food source.