1. Testa epidermis showing thickened polygonal cells (sv).

2. Outer portion of the testa showing epidermal cells and thickened subepidermal cells (ts).

3. Inner portion of the testa showing thinner walled cells (ts).

4. Parenchyma from a cotyledon, with oil droplets (ts).

5. Starch granules.

Akebia trifoliata (Thunb.) Koidz.

Akebia Stem

Caulis Akebiae

Pinyin: Mu tong, san ye mu tong Lardizabalaceae

Akebia is predominantly used in traditional Chinese medicine, where it is classified among herbs that drain dampness. This is partly due the ability of akebia to promote diuresis. According to the Chinese pharmacopoeia (2005), Caulis Akebiae may consist of the stems of either Akebia quinata (Thunb.) Decne. or Akebia tri-foliata (Thunb.) Koidz. There has been a long history of substitution of Akebia spp. with Clematis armandii and Clematis montana (both called chuan mu tong) and Aristolochia manshuriensis (guan mu tong). This confusion continues today. The Clematis species are non-toxic and do not pose a danger in cases of substitution, whereas A. manshuriensis contains toxic aristolochic acids and is no longer included in China's pharmacopoeia or permitted to be sold raw or in products in the United States or European Union. Nonetheless, A. manshuriensis may still be encountered in commerce, potentially as an adulterant of Akebia spp. For the microscopic differentiation of Akebia trifoliata, Aristolochia manshuriensis, Clematis armandii, and Clematis chinensis, see the entry for C. armandii stem. For a complete discussion of AA-containing plants and plants that may be substituted with those containing AA, see AHP (2006a).

Transverse section: The bark may be partially or completely separated from the rest of the stem; narrow, reddish brown cork; primary cortex is composed of thickened parenchyma cells, some with considerably thickened walls and filled with one or several calcium oxalate prisms up to 20 ^m long; between the cortex and secondary phloem, a characteristic, undulating, scalloped ring of fibers occurs, with the convex portions of the ring capping regions of secondary phloem and the concave portions projecting in toward a medullary ray; fibers have a narrow cell lumen and are usually filled with small calcium oxalate prisms up to 10 ^m long; at each medullary ray, the fiber ring is extended into the ray by a narrow radial bundle of somewhat radially elongated sclereids containing prisms; secondary xylem consists of vessels and tracheids arranged in numerous compact, more or less rectangular, regions separated by narrow medullary rays a few cells wide; vessels are up to 150 ^m diameter; rays consist of radially elongated cells that have thin walls in the outer portions and thick walls toward the interior; large pith, with outer cells considerably thickened and pitted, partly filled with several calcium oxalate prisms, and with inner cells of thin-walled parenchyma.

Longitudinal section: Septate fibers; vessel and trac-heid walls are pitted and textured with very fine oblique lines; outer pith cells are somewhat axially elongated.

Starch: Infrequent in cortex and pith; mostly simple, elliptical or rounded polygonal granules are small, up to 14 ^m diameter.

Powder: Fragments of brown or colorless cork are very frequent; large calcium oxalate prism sheaths are around fibers; partially thickened and pitted parenchyma contains compact tabular groups of large calcium oxalate prisms; many fibers are filled with small prisms; few fragments of colorless parenchyma; thickened and pitted parenchyma; narrow tracheids and few bordered-pitted vessels.

Chinese Herbs

Chinese Herbs

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