LEITNERIALES

order of dicotyledonous flowering plants comprising the single rare species Leitneria floridana, the North American corkwood. It is a shrub or small tree found in swampy and riverside localities from southern Missouri to Texas and Florida. Leitneria is characterized by soft, lightweight, close-grained, pale-yellow wood with resin canals; simple, smooth-margined leaves arranged alternately on the stems and lacking stipules (basal appendages); and separate male and female flowers borne on different plants. The flowers are in distinctive clusters called catkins. The male catkins are lax and dangling; those of the female are stiffly erect. The male flowers, which lack petals or sepals, consist of 3 to 12 stamens (male pollen-producing structures) set in the angle of a large, hairy, leaflike bract; 40 to 50 such overlapping bracts make up the male catkin. The female flowers have three to eight small petallike structures at the base of a one-chambered ovary, which encloses one ovule and is prolonged above into a stout elongated upper extension (style). The style is characteristically constricted at the point of union with the ovary and bears the pollen-receptive area (stigma) along one side of the curved upper end. Pollination is by wind. As the corkwood tree is isolated taxonomically, its evolutionary relationships are largely unknown, but it is thought to have ancestors in the witch hazel order (Hamamelidales) or one of its precursors. Leitneria is of little economic importance except for occasional ornamental use.