The principal experience with the tough, light, workable, elastic wood has been in Europe. The ancients used it for shields, because it was one of the woods that would indent without breaking. Lazlett states that it is used for cart-linings because it will not splinter when struck by stones. It has been used for lap-boards, cricket-bats, keels, paddles, and water-wheels. It resists heat and friction and is therefore used for lining friction-brakes. Willow charcoal ignites readily and is highly esteemed in the manufacture of the finer kinds of gunpowder. The bark is used in tanning. The little branches have long been associated with baskets and woven work. American trees are seldom cut up into lumber, but are valued for shade and appearance, and are often planted along the banks of streams to prevent erosion. Willows grow very rapidly and have a characteristic and attractive appearance. They usually prefer low moist places. There are so many hybrids and peculiar species as to render classification in all cases difficult.[50] Black willow is the native species, oftenest attaining to tree size in North America. The White, Crack, Bedford, and Goat Willows (_Salix alba_, _S. fragilis_, _S. russeliana_, and _S. caprea_) are said to afford good wood. _Salix_ is said to be from the Celtic _sal_, meaning near, and _lis_, water. Salicylic acid is abundantly present in the bark of some species. [p089] FOOTNOTE [Footnote 50: About 140 species and varieties of the willow family have been enumerated.] [Illustration: PLATE 17. BLACK WILLOW (_Salix nigra_).] BLACK WILLOW. _Salix nigra Marsh._ Nomenclature. (Sudworth.) Black Willow (local and common name). Swamp Willow (N. C., S. C.). Willow (N. Y., Pa., N. C., S. C., Miss., Tex., Cal., Ky., Mo., Neb.). Locality. New Brunswick to Florida, westward intermittently to Dakota, Arizona, and California, Mexico. Features of Tree. Forty to fifty feet in height, two to four feet in diameter. Long narrow leaf, characteristic appearance. Color, Appearance, or Grain of Wood. Heartwood brown, sapwood nearly white, close-grained. Structural Qualities of Wood. Soft, light, weak, checks badly in drying, readily worked. Dents without splitting. Representative Uses of Wood. Lap-boards, basket-making, fuel, charcoal. Weight of Seasoned Wood in Pounds per Cubic Foot. 27. Modulus of Elasticity. 550,000. Modulus of Rupture. 6000. Remarks. Prefers borders of rivers and bottom lands. Many varieties of willow grow in the United States. No one is used to any extent in construction. [p090] CATALPA. (_Catalpa_.) Many kinds of wood that were formerly plentiful are now much less so. Attention is being turned to trees that give best results under artificial conditions. Catalpa, formerly but little known, now bids fair to become of some importance in this connection.