37 - Ulmaceae

Summary

Monoecious trees. Leaves alternate, simple, serrate, usually asymmetrical at base, petiolate, with stipules when young. Flowers produced before the leaves in small axillary clusters, actinomorphic, hypogynous, bisexual. Perianth shortly (4–)5(–9)-lobed. Stamens the same number as the perianth lobes and opposite them, erect in bud. Styles 2; stigmas linear. Ovary 1-celled, with 1 ovule. Fruit a flattened samara, winged all around, or a small drupe. Contains about 15 genera and some 200 species.

Teeth of leaves usually of 2 sizes, the larger alternating with one or more smaller ones, not mucronate; fruit a winged samara, produced in late spring 1. Ulmus

Teeth of leaves uniform, mucronate; fruit a small drupe, produced in autumn 2. Zelkova

Ulmus L.

By J. V. Armstrong and P. D. S.

Deciduous, monoecious trees, often behaving as shrubs in hedgerows, where they frequently die from Dutch Elm Disease before fully grown, without latex. Trunk often large, erect and straight, sometimes with bosses and burrs, often with epicormic shoots, extending up to three-quarters of the way through the crown; suckers often present. Wood consisting of biseriate and multicellular rays and crystalliferous strands. Bark usually deeply longitudinally furrowed. Branches in mature trees often massive, unarmed, terete, sometimes with corky wings. Buds axillary, covered with brown, ovate, rounded, imbricate, glabrous or hairy scales, the inner ones accrescent and replacing the stipules. Leaves of short shoots alternate; lamina acute or acuminate at apex, serrate, biserrate or occasionally triserrate, with teeth of the length, breadth and depth shown in the drawings, mostly very unequal at the base; stipules lateral, linear-lanceolate to obovate, entire, free or connate at the base, scarious, enclosing the leaf in bud, caducous. Inflorescence a subsessile or pedicellate axillary cyme or raceme; flowers hypogynous, bisexual. Perianth campanulate, with (4–)5(–9) shallow to deep imbricate lobes. Stamens the same number as the perianth lobes; filaments filiform to flattened, straight in bud, exserted after anthesis. Styles 2, deeply 2-lobed, divergent; lobes papillate and stigmatic on the inner face. Ovary sessile or stipitate, compressed, glabrous or hairy, usually unilocular by abortion, rarely bilocular; ovule amphitropous; micropyle extrorse. Asia. If species are accepted as in this account there is no way of estimating the total number.