4. Corylus heterophylla Fischer ex Trautvetter, Pl. Imag. Descr. 10. 1844.
Shrubs or small trees, to 7 m tall; bark gray. Branchlets pubescent and stipitate glandular, with white lenticels. Petiole slender, 1-2(-3) cm, sparsely pubescent; leaf blade oblong, elliptic, elliptic-obovate, broadly ovate, or obovate to suborbicular, 4-13 × 2.5-10 cm, papery, abaxially pilose along veins, adaxially glabrous, base cordate, margin irregularly and doubly serrate, usually lobed, apex mucronate to caudate; lateral veins 3-7 on each side of midvein. Male inflorescences 2-5 in a cluster, pendulous, slender, ca. 4 cm; bracts reddish brown, obovate, densely pubescent, apex acuminate from nearly truncate, apical portion of leaf. Female flowers 2-6 in a cluster; bracts campanulate, 1.5-2.5 cm, striate, densely pubescent and stipitate glandular near base, with triangular-ovate, entire or dentate lobes. Nut ovoid-globose, ca. as long as bracts, 0.7-1.5 cm in diam., apex villous. Fl. May-Jul, fr. Jul-Aug. 2n = 22.
Temperate broad-leaved forests, thickets on mountain slopes; 400-2500 m. Anhui, E and S Gansu, Guizhou, Hebei, Heilongjiang, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, E Nei Mongol, Ningxia, Shaanxi, Shandong, Shanxi, NE Sichuan, Zhejiang [Japan, Korea, Russia (E Siberia)]
The hazelnut of commerce.