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FOC | Family List | FOC Vol. 5 | Ulmaceae

7. Trema Loureiro, Fl. Cochinch. 2: 539, 562. 1790.

山黄麻属 shan huang ma shu

Trees or large shrubs, evergreen. Branchlets never spinose, never corky or winged. Stipules 2, free, caducous, leaving a short transverse scar on each side of leaf base. Leaves alternate in several ranks; leaf blade ovate to narrowly lanceolate, margin denticulate; usually 3(-5)-veined from base (venation pinnate in T. levigata); secondary veins anastomosing before reaching margin. Inflorescences subsessile. Flowers unisexual or polygamous, shortly pedicellate. Male flowers: (4 or)5-lobed; tepals incurved, valvate, or ± imbricate. Stamens equal in number to tepals. Ovary rudimentary, basally with perigynous pubescence. Female flowers: (4 or)5-lobed. Ovary sessile, basally with perigynous pubescence. Drupes 1.5-5 mm in diam., erect, elliptic to ± globose; tepals and stigmas persistent or rarely perianth caducous; exocarp ± fleshy, endocarp bony. Endosperm fleshy; embryo curved or involute; cotyledons narrow.

About 15 species: tropical and subtropical areas; six species (two endemic) in China.

Trema species are often found in E and SW China, particularly in disturbed and degraded habitats.

1 Leaf blade abaxially glabrous except for appressed hairs on major veins.   (2)
+ Leaf blade abaxially pubescent over its whole surface.   (3)
2 (1) Perianth caducous in fruit; leaf blade elliptic-lanceolate to narrowly lanceolate, rarely 3-veined from base.   1 T. levigata
+ Perianth persistent in fruit; leaf blade ovate, ovate-oblong, or rarely lanceolate (in T. cannabina var. cannabina), strongly 3-veined from base.   6 T. cannabina
3 (1) Leaf blade 3-7 × 1-2 cm, abaxially densely white-tomentose, with inconspicuous rust-colored glandular hairs on veins, adaxially very scabrous; petiole 2-5 mm; male flower tepals densely hirsute inside.   5 T. angustifolia
+ Leaf blade (5-)7-22 × 1.5-9(-11) cm, adaxially ± smooth to ± scabrous, without rust-colored glandular hairs on veins; petiole 4-20 mm; male flower tepals not hirsute inside.   (4)
4 (3) Leaf blade abaxially sparsely pubescent, usually with crowded minute dark red sessile glands; petiole 4-8 mm (in T. cannabina var. dielsiana).   6 T. cannabina
+ Leaf blade abaxially densely pubescent, not glandular; petiole 7-20 mm.   (5)
5 (4) Leaf blade lanceolate to narrowly lanceolate, 1.5-4.5 cm wide; inflorescences shorter than petiole.   4 T. nitida
+ Leaf blade ovate, ovate-oblong, or rarely broadly lanceolate, 3-9(-11) cm wide; inflorescences as long as or longer than petiole.   (6)
6 (5) Plant to 10 m tall; fruit rounded-ovoid, 2-3 mm in diam.; leaf blade ± concolor, abaxially with grayish brown pubescence, surface of blade visible between hairs under magnification, adaxially very scabrous with erect bristles.   2 T. tomentosa
+ Plant to 20 m tall; fruit ovoid-globose to ± globose, 3-5 mm in diam.; leaf blade grayish white to grayish green abaxially much paler than adaxially and pubescent, surface completely hidden by hairs, adaxially ± scabrous and usually rugate.   3 T. orientalis

Lower Taxa


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