Monographs Details: Piaropus crassipes (Mart.) Raf.
Authority: Britton, Nathaniel L. Flora Borinqueña.
Description:Species Description - Often floating and covering large areas of fresh-water lakes, ponds or slowly flowing streams, thus locally impeding navigation, this showy-flowered plant grows nearly throughout tropical and subtropical America, from Florida, northern Mexico and Bermuda to Uruguay. In its northern range it has been introduced and naturalized, and there is now difficulty in determining what the original natural distribution actually was. We regard it as native in Porto Rico, where it is occasional, in some places plentiful. The plant is frequently grown in garden pools for ornament and interest. Piaropus (Greek, thick foot, referring to the characteristic, swollen, leaf-stalk of this species) was proposed as a genus by Rafinesque in 1837, who first recognized the differences of these plants from the species of Pontederia; about 5 species, all natives of tropical America are now included. They are perennial, aquatic herbs, their floating or emersed leaves broad, the immersed leaves narrow and grass-like in some species. The clustered or solitary flowers are subtended by narrow, leaf-like bracts (technically spathe); the perianth is oblique, composed of 6 segments united below into a tube; there are 6 stamens, borne on the tube of the perianth, in 2 unequal sets of 3; the 3-celled ovary contains many ovules, the style is slender, the stigma terminal. The fruit is a many-seeded capsule, enclosed in the withering perianth. Piaropus crassipes (Latin, thick foot) floats free, or roots in mud. Its leaves are in a basal tuft, nearly orbicular, or broader than long, firm in texture, smooth, from 3.5 to 16 centimeters in diameter, faintly many-nerved, their stout stalks from 5 to 40 centimeters long, usually much inflated, especially on floating plants. The showy flowers are clustered on a leafless stem from 10 to 35 centimeters long; the usually 2, clasping bracts are from 3 to about 6 centimeters long; the tube of the perianth is curved, glandular-hairy, from 1.5 to 2 centimeters long, its broad segments violet, 3.5 or 4 centimeters long, the upper one somewhat longer than the others, with a blue patch surrounding a bright yellow spot near the middle. Another species, Piaropus diversifolius (diverse leaved), inhabits Porto Rico streams and those of Santo Domingo, Cuba and South America; this has leaves of 2 kinds, one kind broad and floating, from 1.5 to 3.5 centimeters long, the other submersed, narrow, from 3 to 7 centimeters long; its few, small flowers are subtended by a single spathe. This plant is very different in aspect from its relative.

Discussion:Flor de agua Water Hyacinth Pickerel-weed Family Pontederia crassipes Martius, Nova Genera et Species Plantarum 1:9.1824. Piaropus mesomelas Rafinesque, Flora Telluriana 2: 81. 1837. Eichhornia crassipes Solms ; De Candolle, Monographiae Phanerogamarum 4: 527. 1883.