A Taxonomic Study on Dioscorea of Taiwan － Dioscorea batatas

山羊百科，林文智老師的植物、山岳、攝影紀錄

A Taxonomic Study on Dioscorea L. ( Dioscoreaceae ) of Taiwan

Chun Kuei Liao　chunkuei.liao@gmail.com 2000/06

2. Dioscorea batatas Decne. in Rev. Hort. Ser. 4, 3:243. 1854; Bentham, Fl. Hongkong 368. 1861; Prain & Burkill in Journ. Asiat. Soc. Bengal n.s. 10:27. 1914; Knuth in Engl. Pflanzenr. 87(4-43):261,f.55. 1924; Sasaki, List Pl. Form. 113. 1928; Hand.-Mazz., Symb. Sin. 7:1240. 1936; Nemoto, Fl. Jap. Suppl. 1083. 1936; Prain & Burkill, Ann. Bot. Gard. Callcutta 14(2):243. 1939; Ohwi, Fl. Jap. 314. 1965; Liu, T. S. & T. C. Huang in Bot. Bull. Acad. Sin. 3(2):142. 1962; Liu, T. S. & T. C. Huang in Fl. Taiwan 5:101. 1978.

－Dioscorea opposita auct. non Thunb.: Ting, C. T., M. C. Chang & P. P. Ling. in Fl. China 16(1):103, f.33. 1985p. p.

－Dioscorea opposita Knuth, Enum. Pl. 5:390. 1850; Kawakami. List Pl. Form. 122. 1910.

－Dioscorea polystachya Turcz. in Bull. Soc. Nat. Mosc. 8:158. 1837.

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HABIT　DESCRIBE

　A glabrous, scandent vine from annual tuber; underground tuber cylindrical, growing down vertically to 1m long; epidermis greyish or brown; flesh white, edible, never poisonous; aerial stems annual, dextrorse, terete, herbaceous, ridged, green or violet; axillary aerial tubers globose and somewhat irregular branched, 5-15 mm long, 5-10 mm in diameter, greyish, glabrous, with reticulate lines and warts on surface. Leaves opposite or alternate near the base of stem, occasionally whorled, thick chartaceous, ovate-triangular, 3-10(16) cm long, 4-6(14) wide, 3-lobed, acuminate at apex, cordat or hastate or auricalate at base, warped inward, glabrous, green on both surfaces; nerves 7-9, concave at upper surface and convex at lower surface; petioles violet, 1.5-2 cm long, 2-3 mm thick, twisted and dilated at base, sulcate above.

　Staminate inflorescence axillary, spicate, 1-3 together; spikes with 25 flowers, 2-3 cm long; rachis zigzag, greenish, rigid. Male flowers alternate on rachis, globose, 1.5-2 mm in diameter, 2-bracted; outer bract widely ovate, ca. 2.2 mm long, ca. 1.1 mm wide, acuminate at apex; inner bract widely depressed ovate, ca. 1.5 mm long, ca. 1.2 mm wide, acute at apex, round at base; perianths 6, yellow-green with black- brown short-line spots; outer 3 perianths ovate, ca. 1.7 mm long, ca. 1.1 mm wide, obtuse at apex; inner 3 perianths ovate, ca. 1.5 mm long, ca. 1.2 mm wide, acute and thickened at apex; stamens 6, subequal; filament ca. 1.2 mm long, terete; anthers oblong, ca. 0.8 mm long, ca. 0.4 mm wide, dorsifixed, longitudinally dehiscent; pistillodium rudimentary, conicus, ca. 0.5 mm tall; stigmatiform 3-lobed. Pistillate inflorescence spicate, axillary, pendulous. Fruit capsulate, pendulous, tripterous. Seeds orbicular, broadly membranously winged around.

This introduced species has been cultivated for a long time. It has never been collected in the field of Taiwan.

The species is flowering from June to September, fruiting from July to November.

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