CHIEFLY quick-growing, water-loving trees and shrubs, with slender, supple twigs, and buds with a single protective cap or scale of two coats. Wood light, soft. Leaves simple, alter nate, narrow and pointed, deciduous. Flowers dicecious, in loose catkins, each flower subtended by a bract having an entire hairy margin. Fruit a 2-valved pod with papery walls; seeds minute, in copious hairy floats.