The leaves are pale green, and pinnate, somewhat resembling those of the Rowan Tree. Flowers five petalled, creamy white, sometimes very slightly tinged with flesh colour, with a coppery red or violet-purple centre, and disposed in racemes. When fully expanded they are an inch across, and somewhat reflexed. It flowers early in April, with the appearance of the leaves, the blooms being produced in great abundance, in spike-like clusters fully seven inches long, and succeeded by a small green Pear-like fruit. This is one of the most distinct and handsome of recently introduced shrubs, and will, when more widely disseminated, be largely planted for purely ornamental purposes. It grows from 10 feet to about 15 feet high. XANTHORHIZA. XANTHORHIZA APIIFOLIA.--Yellow-root. Pennsylvania, 1776. A small growing shrub, with yellow creeping roots, from which suckers are thrown up profusely. The leaves are irregularly pinnate, and the minute flowers, which are borne in large, branching spikes, are of a peculiar dark purple colour. It prefers a cool, moist situation. YUCCA. YUCCA FILAMENTOSA.--Silk Grass. North America, 1675. A well-known and beautiful plant, with numerous leaves arranged in a dense rosette, and from 1 foot to 2 feet long by 2 inches broad. Flower scape rising to 5 feet or 6 feet in height, and bearing numerous flowers that are each about 2 inches deep. There is a beautiful variegated form of this species named Y. filamentosa variegata, and one with much narrower leaves than the typical species, and known as Y. filamentosa angustifolia. Y. GLORIOSA.--The Mound Lily. United States, 1596. This is another well-known hardy species, with long, sharp-pointed leaves, and a handsome, much branched scape, of flowers that are each about 2 inches deep. There are several varieties, differing in colour of foliage, including Y. gloriosa glaucescens, with decidedly glaucous foliage; Y. gloriosa superba, with rigid leaves and a shorter and denser flower scape; and another with variegated leaves. Y. gloriosa recurvifolia is usually dwarfer in the stem than the type, and more inclined to branch than the other species, and less rigid, with recurving leaves that are not so sharp-pointed, The flower panicle is large and very much branched. The Yuccas all do well if planted in light loam of good quality. ZELKOVA. ZELKOVA ACUMINATA (_syns Z. japonica_ and _Planera acuminata_).--Japan. This resembles very nearly our common Elm in appearance, and being perfectly hardy is to be recommended for planting in this country. Z. CRENATA (_syns Planera crenata_ and _P. Richardi_).--Zelkova Tree. Western Asia to Mount Caucasus, 1760. This is a handsome, large growing tree, with oblong deeply-crenated leaves, and small and inconspicuous flowers. For avenue planting or as a standard specimen this is a valuable tree, being quite hardy, and of free and quick growth. P. crenata pendula is a good weeping form, and worthy of culture.