Leaves broad-obovate, often abruptly dilated at the wide obscurely lobed apex. Leaves rounded or cordate at base. Lower surface of the leaves orange color or brownish, the upper scales of the cup forming with several rows a thick rim on its inner surface, often reflexed. 13. Q. marilandica (A, C). Lower surface of the leaves pale, the erect scales on the rim of the cup in a single row. 14. Q. arkansana (C). Leaves cuneate at base. Leaves oblong-obovate. 15. Q. nigra (C). Leaves rhombic. 16. Q. rhombica (C). Leaves lanceolate-oblong or lanceolate-obovate, usually entire, involute in the bud. Willow Oaks. Leaves glabrous. Leaves lanceolate to oblanceolate, deciduous in autumn. 17. Q. Phellos (A, C). Leaves elliptic or rarely oblong-obovate, deciduous in the late winter. 18. Q. laurifolia (C). Leaves tomentose or pubescent below, oblong-lanceolate to oblong-obovate. Leaves pale blue-green, hoary tomentose below. 19. Q. cinerea (C). Leaves dark green, pubescent below. 20. Q. imbricaria (A). Leaves not deciduous in the autumn, revolute in the bud (convolute in 23). Leaves mostly persistent until after the appearance of those of the following year. Leaves lanceolate, oblong-lanceolate or elliptic, pale and tomentose below. 21. Q. hypoleuca (E, H). Leaves oval, orbicular to oblong, green and pubescent below; fruit maturing at the end of the first season. 22. Q. agrifolia (G). Leaves persistent until their second summer or autumn. Leaves lanceolate to oval or oblong-lanceolate, entire or serrate; cup of the fruit turbinate or tubular. 23. Q. Wislizenii (G). Leaves oval to oblong-obovate; cup of the fruit saucer-shaped or turbinate. 24. Q. myrtifolia (C). Stamens usually 6—8; styles dilated; abortive ovules basal or lateral; leaves persistent until their third or fourth season, involute in the bud. Leaves oblong, entire, dentate, or sinuate-toothed,