Gleditsia aquatica Marsh.

A tree described by Sargent as 50 to 60 ft high, with a trunk 2 to 21⁄2 ft in diameter, but in this country inclined to be shrubby, and to form several stems; spines ultimately about 4 in. long, branched; young shoots not downy, but marked with conspicuous lenticels. Leaves up to 8 in. long, simply or doubly pinnate; leaflets of the pinnate leaf (or of each division of the bipinnate ones) twelve to twenty-four. Each leaflet is lanceolate-oblong, 1 to 11⁄2 in. long, 1⁄4 to 1⁄2 in. wide, rounded, bluntish, or somewhat pointed at the apex, margins wavy, glossy and glabrous except for the down on the short stalk of the leaflet, on the upper side of the main-stalk, and scattered hairs on the margins of the leaflets. Flowers borne on slender racemes 3 or 4 in. long. Pods obliquely diamond-shaped, 13⁄4 in. long, nearly 1 in. wide, not pulpy inside; seeds solitary (rarely two).

Native of the south-eastern United States; introduced in 1723, according to Aiton, but now extremely rare. It is hardy at Kew, but grows slowly. Its small, one-seeded pod well distinguishes it, but so far as is known this has not been borne in cultivation here. The example now at Kew, about 35 ft high and branching at 4 ft, came from the Arnold Arboretum in 1892.