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Ulmus
rubra Muhl. Standardized Common
Name: Slippery Elm
Family: Ulmaceae
Taxonomy: Ulmus
includes about 45 species of trees, widely distributed in North and Central
America and Eurasia. Ulmus rubra is native to North America. It is
genetically and morphologically distinct from the other New World species, but
hybridizes with U. pumila L., a cultivated and probably naturalized
Asian species. A commonly encountered synonym for U. rubra is U.
flava Michx.
Description: Tree to 35 m high,
with spreading branches and open flat crown; trunk to 75 (rarely 100) cm in
diameter, sometimes dividing near base; bark dark brown to reddish,
longitudinally furrowed; young twigs pubescent; buds red-scaled, pubescent with
reddish hairs. Leaves alternate, ovate to elliptical or obovate, 7–16(–20) cm
long; base conspicuously oblique; apex acute to acuminate; margins serrate in
basal portions, biserrate in apical portions, more or less ciliate; upper
surface pubescent with short stiff hairs, rough-textured; lower surface softly
pubescent. Flowers small, inconspicuous, in dense clusters <2.5 cm long;
calyx 5–9-lobed, pubescent with reddish hairs; corolla absent; anthers 5–9,
reddish; styles 2-lobed, pinkish. Fruit a winged achene (samara) with a papery,
broadly elliptical to suborbicular wing, 12–18 mm long.
Parts
in Commerce:
Older inner bark, with outer corky layers removed
Identification:
- Flattened
pieces, often 50–100 cm long
- 1–4 mm thick
- Outer surface
reddish-yellow, longitudinally striated, with occasional reddish or dark
brown patches consisting of remains of cork
- Inner surface
yellow to yellowish-white, longitudinally striated
- Fracture tough
and fibrous
- Odor
characteristic, resembling fenugreek
- Taste
mucilaginous
- Produces
mucilage when moistened
In
cross-section (transverse rather than vertical), narrow parenchyma rays
alternate with broader phloem rays that contain alternating bands of fibers and
mucilage cells, giving a checkered appearance. If a thin cross-section of the
bark is moistened for a few minutes, the large, clear mucilage-containing cells
swell and may be observable using a dissecting microscope at high
magnification. Powdered slippery elm bark swells and produces mucilage (in much
the same way as does Psyllium).
References:
Evans WC. Trease and Evans’ Pharmacognosy, 14th ed. London: WB Saunders
Company Ltd.; 1996:216.
Greenish HG. Materia Medica. Jodhpur: Scientific Publishers (India); 1920
reprinted 1999:281–282.
Sherman-Broyles SL. Ulmus. In: Flora of North
America Editorial Committee, eds. Flora of North America, vol. 3.
New York, NY: Oxford University Press; 1997:369–375.
Wiegrefe SJ. Phylogeny of elms (Ulmus,
Ulmaceae): Molecular evidence for a sectional classification. Syst Bot.
1994;19:590–612.
Youngken HW. Text-Book of Pharmacognosy, 5th ed. Philadelphia, PA: The
Blakiston Company; 1943:272.
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