1. [Ptelea trifoliata] L. Hop-tree. Wafer Ash.
Leaves rarely 5-foliolate on vigorous shoots; leaflets sessile, ovate or oblong, pointed, the terminal leaflet generally larger and more gradually contracted at base than the others, entire or finely serrate, covered at first with short close pubescence, becoming glabrous and rather coriaceous at maturity, dark green and lustrous above, pale below, 4′—6′ long, 2½′—3′ wide, with a prominent midrib and primary veins; turning clear yellow in the autumn before falling; petioles stout, thickened at base, 2½′—3′ in length. Flowers appearing in early spring on slender pubescent pedicels 1′—1½′ long, the pistillate and staminate flowers produced together, the staminate usually less numerous and falling soon after the opening of the anther-cells; calyx and petals pubescent; ovary puberulous. Fruit with a thin almost orbicular sometimes slightly obovate wing, nearly 1′ across, on a long slender reflexed pedicel, in dense drooping clusters remaining on the branches through the winter; seeds ⅓′ long, dark red-brown.
A round-headed tree, rarely 20°—25° high, with a straight slender trunk 6′—8′ in diameter, small spreading or erect branches, and slender branchlets covered at first with short fine pubescence, becoming glabrous, dark brown and lustrous, and marked by wart-like excrescences and by the conspicuous leaf-scars; more often a low spreading shrub. Winter-buds depressed, nearly round, pale or almost white. Wood heavy, hard, close-grained, yellow-brown, with thin hardly distinguishable sapwood of 6—8 layers of annual growth. The bitter bark of the roots is sometimes used in the form of tinctures and fluid extracts as a tonic, and the fruit is occasionally employed domestically as a substitute for hops in brewing beer.
Distribution. Generally on rocky slopes near the borders of the forest, often in the shade of other trees; Long Island, New York, Pennsylvania, and westward through southwestern Ontario (Point Pelee) and southern Michigan to southern Iowa, southeastern Nebraska, and southward to Georgia, Alabama, eastern Louisiana and through Missouri and Arkansas to southeastern Kansas, eastern Oklahoma and eastern Texas. A form with leaflets soft-pubescent on the lower surface (var. mollis T. & G.) occurs in the south Atlantic states from North Carolina to Florida.
Often planted as an ornament of parks and gardens.
4. AMYRIS L.
Glabrous glandular-punctate trees or shrubs, with balsamic resinous juices. Leaves opposite or rarely opposite and alternate, 3-foliolate, without stipules, persistent; leaflets opposite, petiolulate, entire or crenate. Flowers white, minute, on slender bibracteolate pedicels, usually in 3-flowered corymbs in terminal or axillary branched panicles; calyx 4-toothed, persistent; petals 4, hypogynous, much larger than the calyx-lobes, spreading at maturity; disk of the staminate flower inconspicuous, that of the pistillate and perfect flowers thickened and pulvinate; stamens 8, hypogynous, opposite and alternate with the petals; filaments filiform, exserted; anthers ovoid, attached on the back below the middle; ovary ellipsoid or ovoid, 1-celled, rudimentary in the staminate flower; style short, terminal, or wanting; stigma capitate; ovules collateral, suspended near the apex of the ovary, anatropous. Fruit a globose or ovoid aromatic drupe; stone 1-seeded by abortion, chartaceous. Seed pendulous, without albumen; seed-coat membranaceous; cotyledons plano-convex, fleshy, glandular-punctate.
Amyris is confined to tropical America and northern Mexico. Of the twelve or fourteen species which have been distinguished two extend into the territory of the United States; one of these is a small West Indian tree common on the shores of southern Florida, and the other, Amyris parvifolia A. Gray, a Mexican shrub, grows in Texas near Corpus Christi, Neuces County, and near the mouth of the Rio Grande. Amyris is fragrant and yields a balsamic aromatic and stimulant resin, and heavy hard close-grained wood valuable as fuel and sometimes used in cabinet-making.
The generic name, from μύῤῥα, relates to the balsamic properties of the plants of this genus.