Which is the smallest flower in the world?

The smallest individual flowering plant is watermeal, a member of the duckweed family. The plant itself is 1/32 of an inch in width, or about the size of a pinhead. The light green free-floating, rootless plant grows in lakes and ponds, and weighs about 1/190,000 of an ounce, equivalent to two grains of table salt. They are very hard to see; in fact, you would need about 5,000 plants to fill up one thimble. However, because they grow in colonies, these plants look like algae spreading across the water. Their capacity to reproduce very quickly can cause a pond to be completely covered in the green plants in just a few weeks.