Description from Flora of China
Quercus stenophylloides Hayata, Icon. Pl. Formosan. 4: 21. 1914; Cyclobalanopsis stenophylla (Blume) Schottky var. stenophylloides (Hayata) J. C. Liao; Q. salicina Blume var. stenophylloides (Hayata) S. S. Ying; Q. stenophylla (Blume) Makino var. stenophylloides (Hayata) A. Camus.
Trees to 17 m tall. Branchlets slender, gray, glabrous. Petiole 1.5-2 cm, glabrous; leaf blade oblong-elliptic to lanceolate, 7-12 × 1.5-3.5 cm, leathery, abaxially farinose and with prostrate simple hairs but usually glabrescent, adaxially green, base narrowly acute to rounded, margin with short, awnlike serrations, apex acuminate to caudate; secondary veins 11-13 on each side of midvein, extending into serration; tertiary veins abaxially inconspicuous to obscure. Female inflorescences 2-2.5 cm, cupules 6 or 7. Cupule cupular, 1-1.5 × ca. 1.2 cm, enclosing ca. 1/2 or less of nut, outside and inside grayish velutinous, wall less than 1 mm thick; bracts in 6 or 8 rings, margin dentate. Nut ellipsoid, 1.7-2 × ca. 1.5 cm, glabrous; scar ca. 5 mm in diam., flat; stylopodium persistent, conspicuous, 3-ringed. Fl. Apr-May, fr. Sep-Oct of following year.
The Japanese Cyclobalanopsis salicina (Blume) Oersted has been reported in Taiwan (J. C. Liao, Fl. Taiwan, ed. 2, 2: 84. 1996). Cyclobalanopsis salicina and C. stenophylloides are very closely related, but the plants in Taiwan are apparently populations of C. stenophylloides growing on sandstone ridges at lower elevations than is typical for this species.
* Broad-leaved evergreen forests in mountains; (500-)1100-2600 m. C to N Taiwan