Quercus mcvaughii Spellenb.

Mexico (Chihuahua, Durango, Sonora, San Luis Potosi) ; 1500-3100 m;

reaches more than 20 m tall; sometimes shrubby;

6-15 cm long, 4-10 wide; broadly oboval or rounded; leathery; thick; convex; apex obtuse or rounded, seldom acute or acuminate, bristle-tipped; base progressively attenuate, abruptly rounded or slightly cordate, sometimes truncate; margin thick, revolute, cartilaginous, with 3-7 pairs of small teeth, ending in 2 mm long bristle, seldom margin subentire; dark green, lustrous, nearly hairless above, except fascicled and glandular hairs along midrib; dense tomentum beneath, yellowish white, made of numerous 4-10 rayed, sinuous, tangled stipited fascicled trichomes (stalk to 0.05 mm , with a lot of white and yellow glandular hairs; 6-10 vein pairs slightly curved, strongly impressed adaxially; epidermis slightly bullate and papillose, invisible under tomentum; petiole 1-3.5 cm long, persistently tomentose;

in April-May; male catkins 3-8 cm long, few-flowered; female ones bearing 1 or 2 flowers;

acorn 1-2 cm long; subsessile or on a 0.5-1 cm long peduncle; singly or paired; cup pubescent, margin not rolled under, 9-11 mm in diameter, 6-8 mm high, enclosing 1/3 of nut; maturing in 2 years between July and September;

– Sub-genus Quercus, section Lobatae, Series Erythromexicanae; – Related to Q.crassifolia, of which it is a variety for Zavala-Chavez, 2003; – Possible confusion with Q. crassifolia, Q. fulva and Q. conzattii ; Q. crassifolia differs in having the stalk of abaxial fasciculate trichomes longer (0.2 mm); Q. conzattii differs in the annual maturation of acorn, the cupule peduncle longer (10-15 mm), and more acorns on the same peduncle (to 5 or more); Q. fulva has a cupule 13-18 mm in diameter with margin rolled inside, and the abaxial foliar trichomes with 10-25 rays, 0.4-0.7 mm long;