Deciduous shrubs or small trees with petiolate venose leaves and pure white flowers on slender drooping pedicels, solitary or in small clusters from the buds of the preceding year. Calyx-tube adherent to the ovary, surmounted by 4 small teeth. Petals 4, united to about the middle in a bell-shaped corolla. Stamens 8 to 16, united in a ring at the base of the corolla. Fruit dry, 2- to 4-winged, with 1 to 4 bony 1-seeded cells. There are only three or four species, all limited to North America. This genus commemorates the celebrated Dr. Hales, author of ' Vegetable Statics,' etc.

1. H. tetroptera. Common Snowdrop Tree. - This is the species commonly cultivated. It is distinguished by its 4-winged fruit, which is from 1 to 2 inches long. The flowers somewhat resemble in size and outward appearance those of the common Snowdrop. They are produced in April or May before the leaves have attained their full development. This and the other species are popularly known under the name of Silver-bell trees. II. diptera, as the name indicates, has usually a 2-winged fruit; and H. parviflora is a species with smaller flowers.

Styrax officinalis, which furnishes the Storax of the shops, is a native of Asia Minor and South of Europe, and is occasionally' seen in English gardens, but being rather tender it is comparatively rare. It is a small deciduous shrub in this country, with ovate leaves shaggy beneath, and racemes of white flowers about an inch or a little more in diameter. The fruit is spherical, usually 1-celled by abortion, and enclosed within the calyx-tube. There are besides the above three or four hardy North American species very desirable on account of the profusion of their showy white flowers, but they are almost unknown in this country. The foliage is more or less clothed with a stellate or scurfy indumentum.

The genus Symplocos comprises many species, chiefly from the tropical and warmer parts of Asia and America. It is characterised by having a 5-lobed calyx adhering to the base of the ovary, 5 petals slightly combined at the base, and very many stamens in several series. The flowers too are yellow, and the pubescence not stellate. S. Japonica is a Japanese shrubby species of recent introduction; and 8. tinctoria is a very fragrant North American species known under the names of Sweet-leaf and Horse-sugar, from the fondness evinced by animals for browsing upon its sweet foliage.