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FOC | Family List | FOC Vol. 5 | Ulmaceae

1. Ulmus Linnaeus, Sp. Pl. 1: 225. 1753.

榆属 yu shu

Trees or shrubs, deciduous or evergreen. Branchlets never spinose, sometimes with a thick and irregularly longitudinally fissured corky layer or with 2 flat opposite corky wings. Bud scales imbricate, glabrous or pubescent. Stipules 2, lanceolate-ovate to linear, membranous, caducous, leaving a short transverse scar on each side of leaf base. Leaves distichous, blade base ± oblique, margin doubly or simply serrate; venation pinnate; secondary veins extending to margin, each ending in a tooth. Bracteoles at base of pedicels, membranous. Pedicel shorter than to almost as long as perianth, pubescent or rarely glabrous. Flowers bisexual or polygamous, appearing in spring before leaves, rarely in autumn or winter. Perianth 4-9-lobed, usually campanulate; tepals membranous, usually persistent, apex usually lacinulate. Stamens equal in number to tepals; filaments flat; anthers extrorse. Ovary flat; ovule pendulous, amphitropous. Style very short or rarely slightly elongate and bifid; stigmas 2, linear, pubescent. Samara flat, orbicular, obovate, oblong, elliptic, or rarely shuttle-shaped, wings membranous, apex with notch and persistent stigmas. Seed at center or toward apex of samara, compressed or ± convex, without endosperm; embryo erect; cotyledon flat or ± convex.

About 40 species: Asia, Europe, North America; 21 species (14 endemic) in China.

Many species yield fine woods, edible fruit, and medicinal products.

Many Chinese Ulmus species are cultivated in areas beyond their native range. In addition, the non-native species Ulmus americana Linnaeus, U. densa Litvinov, and U. laevis Pallas are grown as cultivated plants in China.

1 Evergreen trees; samaras strongly asymmetric, orange-brown.   20 U. lanceifolia
+ Deciduous trees; samaras symmetric or weakly asymmetric, tan, light brown, pale green, or whitish (rarely slightly orange- or red-brown in U. macrocarpa and U. parvifolia).   (2)
2 (1) Flowers and fruit appearing late summer to early autumn.   21 U. parvifolia
+ Flowers and fruit appearing in spring.   (3)
3 (2) Inflorescences racemose cymes or short cymes; peduncle slightly elongated to very noticeably elongated, pendulous; pedicel 2-4 × as long as perianth.   1 U. elongata
+ Inflorescences fascicled cymes or fasciculate; peduncle extremely short, not pendulous; pedicel almost as long as or rarely longer than perianth.   (4)
4 (3) Seed at center or toward apex of samara; seed apex reaching notch (apex sometimes only nearly to notch in U. glaucescens).   (5)
+ Seed at center or slightly toward base of samara; seed apex not reaching notch (apex sometimes near to notch in U. pumila).   (12)
5 (4) Flowers developed from mixed buds thus samaras usually on short shoots with one or a few leaves; leaves 1-3 cm wide, both surfaces pubescent or subglabrous, often with tufts of hairs abaxially in forkings of secondary veins (never in vein axils); samara wings relatively thick; seed broader than wings.   12 U. glaucescens
+ Flowers developed from floral buds thus no leaves attached within each cluster of samaras; leaves 1.5-10 cm wide, variously pubescent or glabrous but often with tufts of hairs abaxially in vein axils (never in forkings of secondary veins); samara wings thin; seed narrower than wings.   (6)
6 (5) Samara ± pubescent.   13 U. chenmoui
+ Samara glabrous except for notch or pubescent only on seed.   (7)
7 (6) Leaf blade abaxially densely pubescent.   19 U. castaneifolia
+ Leaf blade abaxially glabrous or sparsely pubescent.   (8)
8 (7) Branchlets densely pubescent.   18 U. androssowii var. subhirsuta
+ Branchlets glabrous or sparsely pubescent.   (9)
9 (8) Samara obovate to ± obovate or oblong-elliptic to oblong-obovate.   (10)
+ Samara ± orbicular to ovate-orbicular.   (11)
10 (9) Samara obovate to ± obovate; branchlets sometimes with a corky layer.   14 U. davidiana
+ Samara oblong-elliptic to oblong-obovate; branchlets without a corky layer.   15 U. prunifolia
11 (9) Samara 7-8 × 7-8 mm; leaf blade 8.5-17 cm; petiole ca. 5 mm.   16 U. microcarpa
+ Samara 11-16 × 9-13 mm; leaf blade 2-9 cm; petiole 5-12 mm.   17 U. szechuanica
12 (4) Samara pubescent.   (13)
+ Samara glabrous or pubescent only on stigmatic surface.   (16)
13 (12) Leaf blade abaxially glabrous and ± scabrous, adaxially sparsely pubescent when young but glabrescent, margin serrate with acute teeth; bud scales glabrous.   5 U. changii
+ Leaf blade abaxially ± pubescent and scabrous or not, adaxially scabrous and densely hirsute, margin rounded serrate; bud scales ± pubescent.   (14)
14 (13) Flowers developed from mixed buds; bark irregularly exfoliating, gray to grayish white.   4 U. lamellosa
+ Flowers developed from floral buds or mixed buds; bark longitudinally fissured, gray to blackish gray.   (15)
15 (14) Branchlets pubescent; leaf blade apex obtuse-acuminate to acute; samara 1.8-2.8 × 1.7-2.7 cm.   2 U. gaussenii
+ Branchlets glabrous or sparsely pubescent; leaf blade apex acuminate or shortly caudate; samara 1.5-4.7 × 1-3.9 cm.   3 U. macrocarpa
16 (12) Leaf blade apically 3-7-lobed; pedicel glabrous.   6 U. laciniata
+ Leaf blade apically not lobed; pedicel pubescent.   (17)
17 (16) Leaf blade 5-18 × 3-8.5 cm, apically narrowly acuminate to caudate; winter buds glabrous or variously pubescent.   (18)
+ Leaf blade 2-8 × 1.2-3.5 cm, apically acuminate to cuspidate; winter bud scale margin usually white-ciliate.   (20)
18 (17) Winter buds ± pubescent, margin of bud scales prominently long ciliate; twigs sometimes conspicuously winged; samaras 1.5-4.7 × 1-3.9 cm.   3 U. macrocarpa
+ Winter buds finely and inconspicuously puberulent, margin of bud scales entire or inconspicuously short-ciliate; twigs never winged; samaras 1-1.8 × 0.8-1.6 cm.   (19)
19 (18) Leaf blade 5-11 × 3-4.5 cm, abaxially pubescent, base ± oblique to ± symmetric; secondary veins 11-20 on each side of midvein; samara 8-10 mm wide.   8 U. uyematsui
+ Leaf blade 6-18 × 3-8.5 cm, abaxially glabrous or pubescent, base distinctly oblique; secondary veins 17-26 on each side of midvein; samara 10-16 mm wide.   7 U. bergmanniana
20 (17) Leaf blade pubescent; petiole pubescent; samara wings relatively thick.   11 U. pseudopropinqua
+ Leaf blade smooth and glabrous or with tufts of hair in vein axils; petiole glabrous or pubescent; samara wings relatively thin.   (21)
21 (20) Leaf blade margin simply serrate or sparsely doubly serrate; base symmetric to ± oblique.   9 U. pumila
+ Leaf blade margin doubly serrate; base oblique.   10 U. harbinensis

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