9. Quercus tardifolia C. H. Muller, Bull. Torrey Bot. Club. 63: 154. 1936.
Trees , evergreen. Bark gray, furrowed. Twigs dark reddish brown, 1.5-2.5 mm diam., densely pubescent. Terminal buds brown or reddish brown, ellipsoid or ovoid, 3.5-5.5 mm, apex hairy, scales with ciliate margins. Leaves: petiole 10-20 mm, pubescent or glabrate. Leaf blade broadly elliptic or obovate, widest at or distal to middle, planar, 50-100 × 20-70 mm, base cordate or occasionally rounded, margins with 3-4 lobes with shallow sinuses, 6-12 awns, apex acute or obtuse; surfaces abaxially conspicuously tomentose, primary and secondary veins raised, adaxially somewhat rugose, glabrate. Acorns biennial, immature acorns in pairs, mature acorns not known.
Flowering spring. Wooded arroyos; of conservation concern; 2000 m; Tex.
Quercus tardifolia was reported from Mexico (Coahuila) (A. M. Powell 1988), but I have not seen the specimens. It should be expected in the ranges (e.g., Sierra del Carmen) adjacent to the Big Bend area.
This distinctive species is apparently quite infrequent, only two small clumps being known from the Chisos Mountains (C. H. Muller 1951). Recent efforts to locate Quercus tardifolia have not been successful (M. Powell, pers. comm.). Its status is also in question; Muller and K. C. Nixon (pers. comm.) think that it might be a hybrid between Quercus gravesii and Q . hypoxantha .