S. DISCOLOR ARIAEFOLIA (_syn S. ariaefolia_).--White Beam-leaved Spiraea. North-west America, 1827. This forms a dense, erect shrub about 6 feet high, with elliptic-oblong leaves, and clothed beneath with a whitish tomentum. The flowers are in large, terminal, slender-stalked panicles, and white or yellowish-white. It is one of the handsomest species in cultivation, the neat and yet not stiff habit, and pretty, plume-like tufts of flowers making it a general favourite with the cultivators of hardy shrubs. Flowers about mid-summer. In rich soils, and where partially shaded from cold winds, it thrives best. S. DOUGLASII.--Douglas's Spiraea. North-west America. This has long, obovate-lanceolate leaves, that are white with down on the under surface, and bears dense, oblong, terminal panicles of rosy flowers. S. Douglasii Nobleana (Noble's Spiraea) is a variety of great beauty, growing about a yard high, with large leaves often 4 inches long, and looser panicles of purple-red flowers. Flowering in July. The variety was introduced from California in 1859. S. FISSA.--Split-leaved Spiraea. Mexico, 1839. A stout, erect-growing shrub, about 8 feet high, with rather small leaves, angular, downy branches, and long, loose, terminal panicles of small and greenish-white flowers. The leaves are wedge-shaped at the base, and when young have the lateral incisions split into a pair of unequal and very sharp teeth. Flowering in May and June. In the south and west of England it thrives best. S. HYPERICIFOLIA (_syn S. flagellata_).--Asia Minor, 1640. A wiry twiggy shrub, fully 4 feet high, with entire leaves, and small, white flowers produced in umbels at the tips of the last year's shoots. It is a pretty and desirable species. S. JAPONICA (_syns S. callosa_ and _S. Fortunei_).--Japanese Spiraea. China and Japan, 1859. This is a robust species about a yard high, with large lanceolate leaves, and small, rosy-red flowers arranged in corymbose heads. Flowering at mid-summer. There are several fine varieties of this species, including S. japonica alba, a compact bush about a foot high with white flowers; S. japonica rubra differs from the type in having dark red flowers; S. japonica splendens, is a free-flowering dwarf plant, with peach-coloured flowers and suitable for forcing; and S. japonica superba, has dark rose-red flowers. S. Bumalda is a closely allied form, if not a mere variety of S. japonica. It is of dwarf habit, with dark reddish-purple flowers. S. LAEVIGATA (_syns S. altaicensis_ and _S. altaica_).--Smooth Spiraea. Siberia, 1774. A stout, spreading shrub about a yard high, with large, oblong-lanceolate, smooth, and stalkless leaves. The white flowers are arranged in racemose panicles, and produced in May.