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 False Acacia, Common Acacia, Robinia, or Locust-tree, as it is variously styled, is a native of mountain forests in North America, attaining its greatest perfection in Kentucky and Tennessee, where it attains the height of ninety feet and a diameter of four feet. It has been grown in this country for two hundred and fifty years, it being one of the earliest trees introduced from the New World, its graceful habit and light pinnate leaves commending it as an ornamental tree for the plantation. In the United States it is in great repute as an ornament, a shade or a timber-tree; it grows with great rapidity, and its timber is of great durability, so that our cousins use it largely for ship-building, railway sleepers, and fences. When William Cobbett visited the States he was greatly struck with the useful nature of this tree, and on his return to England spared no pains to make its virtues known to his countrymen, even starting a nursery for the purpose of supplying the young trees, and creating quite a rage for Locust-planting for several years.
The leaves are long, compound, the leaflets being arranged in a pinnate manner, with an odd leaflet. The stipules are in the form of prickles at the base of the leaf-stalk. It is a Leguminous plant, and its flowers greatly resemble those of the pea. They are white, sweet-scented, and gathered into a long, pendulous raceme, like that of the laburnum: May and June. The tree is sensitive, and on a branch being touched the leaves will all incline towards the branch, whilst each leaflet advances half-way towards its opposite fellow. The same movements occur at sunset, the leaflets then remaining folded face to face until dawn. The fruit (shown in figure) is that form of pod called a lomentum, in which the valves are constricted between the seeds.