This section is from the book "Wayside And Woodland Blossoms", by Edward Step. Also available from Amazon: Wayside And Woodland Blossoms: A Guide To British Wild-Flowers.
The Alder, of which we have but one species, is own cousin to the Birch, but we must not seek it in similar situations. The Birch loves the breezy hillside, the Alder prefers the swampy valley, the pond and river-side, its tastes being more thoroughly aquatic even than those of the Willows. Its bark has some resemblance to that of the Birch, especially when young, but in later lifeis more rugged, and very dark. The leaves are nearly round, doubly toothed, and with short stalks. When young they are sticky, as are the young shoots. The male catkins are long, produced, like those of the Hazel, late in autumn ; the round red scales each holding three flowers, consisting of three, four or five sepals, and as many stamens. The female spikes are not produced till spring: they are more globular, and resemble minute cedar cones. The scales are reddish-brown and fleshy, afterwards becoming hard and woody; there are two or three flowers in each, consisting of two sepals, an ovary and two styles. When ripe (October) the thick scales separate and set free the pale-brown nuts, which are very slightly winged.
Alnus glutinosa. - Cupuliferae. In suitable situations the Alder attains a stature of forty to sixty feet, and reaches maturity in about sixty years. The wood is soft and white, but turns orange by exposure after cutting. Under water it is very enduring, all but imperishable, and the Rialto at Venice is said to be built on Alder-piles. It is greatly used in the manufacture of gunpowder.
Ainus is the old Latin name for the tree, and for a boat.