The smallest flowering plant in existence is Wolffia microscopica, a native of India. It belongs to the natural order Lemnaceae, or the Duckweed Family. It is almost microscopic in size, destitute of proper stem, leaves and roots, but having these organs merged in one, forming a frond. There is, however, a prolongation of the lower surface into a kind of rhizoid, the purpose of which seems to be to enable the plant to float upright in the water. The fronds multiply asexually by sending out other fronds from a basilar slit, or concavity, and with such rapidity does this take place that a few days often suffices to produce from a few individuals enough similar ones to cover many square rods of pond surface with the minute green granules.

But small as these plants are, and simple in their structure, they yet produce flowers. Two flowers are produced on a plant, each of them very simple, one consisting of a single stamen, and the other of a single pistil, both of which burst through the upper surface of the frond. There are two species of this genus growing in the Eastern United States, one of them, Wolffia Columbiana, about 1.25 of an inch in diameter and the other, W. Brasiliensis, somewhat smaller in size. The American species has been collected near Philadelphia.