Description from Flora of China
Phaseolus max Linnaeus, Sp. Pl. 2: 725. 1753; Dolichos soja Linnaeus; Glycine angustifolia Miquel; G. hispida (Moench) Maximowicz; Soja angustifolia Miquel; S. hispida Moench; S. japonica Savi; S. max (Linnaeus) Piper; S. viridis Savi.
Herbs annual, 0.3-0.9 m tall. Stems robust, erect, sometimes ± twining at apex, ± ribbed, densely brown hirsute. Leaves usually pinnately 3-foliolate; stipules broadly ovate, 3-7 mm, acuminate, densely yellow villous; petiole 2-20 cm, sparsely pubescent or hirsute when young; stipels lanceolate, 1-2 mm; petiolules 1.5-4 mm, hirsute; leaflets papery, broadly ovate, almost circular, or elliptic-lanceolate, terminal one larger, 5-12 × 2.5-8 cm, base broadly cuneate or rounded, apex acuminate or ± rounded, mucronate; lateral leaflets smaller, obliquely ovate. Raceme short or long; peduncle 1-3.5 cm; bracts lanceolate, 2-3 mm, strigose. Flowers few to many, those on lower part of stem sometimes solitary or 1 pair between 2 axils; bracteoles lanceolate, 2-3 mm, hirsute. Calyx 4-6 mm, densely long hirsute and strigose, usually 2-lipped; lobes 5, lanceolate, upper 2 connate to above middle, lower 3 separate, all densely white villous. Corolla purple, light purple, or white, 4.5-8(-10) mm; standard obovate-suborbicular, base clawed, apex slightly emarginate and usually reflexed; wings crenate, base narrow, with claws and auricles; keels obliquely obovate, with short claws. Ovary with undeveloped glands at base, hairy. Legume succulent, oblong, slightly curved, pendulous, 40-75 × 8-15 mm, densely silky hairy. Seeds 2-5, elliptic, suborbicular, or ovate to oblong, ca. 10 × 5-8 mm, many colored; testa smooth; hilum obvious, elliptic. Fl. Jun-Jul, fr. Jul-Sep. 2n = 40.
It has been estimated that Glycine max, soybean, provides ca. 35% of human protein (X. Bao et al., FAO/IBPGR Plant Genetic Resources Newsletter 94/95: 1-3. 1993). It is also an important source of oil and used extensively industrially.
There seems very little doubt that Glycine max, not known as a wild plant, has been selected from the following species, G. soja. It has been confused nomenclaturally with that species.
Cultivated throughout China [now cultivated throughout temperate and tropical regions].