Alder, the English name of the small genus Alnus, shrubs or trees belonging, with the birches, to the order Betulaceae, native to the North Temperate and Arctic zones and to the Andes into Chili. They are characterised by the scales of the female catkin becoming woody, so as to form a permanent fir-cone-like structure. Our one British species, A. glutinosa, has roundish, short-stalked leaves, with wedge-shaped base and slightly-toothed margin, hairy and glutinous when young, dark green and glossy when older. It may reach seventy feet in height and nine in girth, but seldom exceeds forty in height, and is commonly treated as coppice. It grows well by water, its roots binding together the banks. The bark of the shoots (which are generally somewhat triangular in section, as is also their pith) is used in tanning and dyeing leather red, brown, yellow, or, with copperas, black. The wood is durable under water, and is said by Virgil to have been the first wood used by man for boats. It was used for piles at Ravenna and for the Rialto at Venice, and is still so employed in Holland. It is also used for herring-barrels, for sabots and turnery generally, and, of late, for paper-making; but its chief use is for gunpowder-charcoal. For this purpose shoots five or six years old, or about four inches across, are employed.