=Búxus sempérvirens=, L. (BOXWOOD.) Leaves ovate, smooth, dark green; leaf-stems hairy at edge. This plant is a native of Europe, and in its tree form furnishes the white wood used for wood-engraving. Var. _subfruticosa_ (dwarf boxwood) grows only a foot or two high, and is extensively used for edgings in gardens. The tree form is more rare in cultivation, and is of slow growth, but forms a round-topped tree. ORDER =XXXVI. URTICÀCEÆ.= (NETTLE FAMILY.) A large order of herbs, shrubs and trees, mainly tropical. GENUS =74. ÚLMUS.= Tall umbrella-shaped trees with watery juice and alternate, 2-ranked, simple, deciduous, obliquely ovate to obliquely heart-shaped, strongly straight-veined, serrate leaves, harsh to the touch, often rough. Flowers insignificant, appearing before the leaves. Fruit a flattened, round-winged samara; ripe in the spring and dropping early from the trees. Bark rough with longitudinal ridges. * Leaves very rough on the upper side. (=A.=) =A.= Leaves 4 to 8 in. long; buds rusty-downy; inner bark very mucilaginous 1. =A.= Leaves smaller; buds not downy; cultivated. (=B.=) =B.= Wide-spreading tree; twigs drooping; fruit slightly notched 2. =B.= Tree rather pyramidal; twigs not usually drooping; fruit deeply notched 3. * Leaves not very rough on the upper side. (=C.=) =C.= Buds and branchlets pubescent; twigs often with corky ridges 4. =C.= Buds and branchlets free from hairs, or very nearly so. (=D.=) =D.= Twigs with corky wings 5. =D.= Twigs often with corky ridges; cultivated 2, 3. =D.= Branchlets never corky 6. [Illustration: U. fúlva.] 1. =Úlmus fúlva=, Michx. (SLIPPERY OR RED ELM.) Leaves large, 4 to 8 in., very rough above, ovate-oblong, taper-pointed, doubly serrate, soft-downy beneath; branchlets downy; inner bark very mucilaginous; leaves sweet-scented in drying; buds in spring soft and downy with rusty hairs. Fruit with a shallow notch in the wing not nearly reaching the rounded nut. A medium-sized tree, 45 to 60 ft. high, with tough and very durable reddish wood; wild in rich soils throughout. [Illustration: U. montàna.]