Quercus sect. Protobalanus
Chênes 1: 157. 1938.
Trees or shrubs, evergreen. Bark grayish white to reddish brown, scaly to smooth with furrows. Leaf blade never lobed, margins entire or toothed, teeth if present usually spinose. Staminate flowers: calyx 5-6-lobed; anthers attenuate-apiculate. Pistillate flowers: calyx adnate to ovary, not forming flange; styles short and dilated to long and abruptly enlarged. Acorns: maturation biennial; cup pedunculate, cup scales distinct or laterally connate, base thickened and corky (tuberculate); nut with inner wall densely to sparsely tomentose, abortive ovules apical to lateral or basal, sometimes variable within individual plants, seed coats adhering to seed, sometimes to fruit wall at maturity. Cotyledons distinct.
sw North America and nw Mexico.
Quercus Linneaus subg. Protobalanus Trelease in P. C. Standley, Contr. U.S. Natl. Herb. 23: 176. 1922
Measurements for the cup of the acorn in the next two sections is for depth of cup, not height.
Species 5 (4 in the flora).
|1||Twigs rigid, 1.5–3 mm diam., branching at 65–90° angles; cup scales obscured, laterally connate into concentric rings; nut oblong to fusiform.||Quercus palmeri|
|1||Twigs flexible, if stiff 3–4 mm diam., branching at less than 60° angles; cup scales often laterally connate and embedded in tomentum, not in noticeable concentric rings; nut ovoid.||> 2|
|2||Leaf blade glossy dark green, brittle, margins entire to mucronately toothed, often strongly revolute; surfaces abaxially densely tomentose.||Quercus tomentella|
|2||Leaf blade dull gray-green to yellowish green, leathery, margins entire to spinescent or mucronately toothed, usually flat; surfaces abaxially glabrous or pubescent, not tomentose.||> 3|
|3||Shrubs; leaf margins entire to mucronately toothed, surfaces glabrous or pubescent with sparse cover of minute stellate hairs, glandular hairs absent; nut 8–17 mm, cup thin, 10–15 mm wide; nut scar to 3 mm diam.||Quercus vacciniifolia|
|3||Trees or large shrubs; leaf margins entire to spinescent, surfaces glabrate to pubescent with golden glandular and multiradiate hairs; nut 15–30 mm, cup thick, 15–40 mm wide; nut scar 4–10 mm diam.||Quercus chrysolepis|