Sterile flowers in slender naked catkins; bracts caducous; calyx 2–8-parted or lobed; stamens 3–12; anthers 2-celled. Fertile flowers scattered or somewhat clustered, consisting of a nearly 3-celled and 6-ovuled ovary, with a 3-lobed stigma, enclosed by a scaly bud-like involucre which becomes an indurated cup (cupule) around the base of the rounded nut or acorn. Cotyledons remaining underground in germination; radicle very short, included.—Flowers greenish or yellowish. Sterile catkins single or often several from the same lateral scaly bud, filiform and hanging in all our species. (The classical Latin name.) All flower in spring, and shed their nuts in Oct. of the same or the next year.
§ 1. LEUCOBÁLANUS. Bark pale, often scaly; leaves and their lobes or teeth obtuse, never bristle-pointed; stamens 6–8; scales of the cup more or less knobby at base; stigmas sessile or nearly so; abortive ovules at the base of the perfect seed; inner surface of nut glabrous; fruit maturing the first year, often peduncled; kernel commonly sweetish; wood tough and dense.
[*] Leaves deciduous, lyrate or sinuate-pinnatifid, pale beneath.—White Oaks.
1. Q. álba, L. (White Oak.) Mature leaves smooth, pale or glaucous underneath, bright green above, obovate-oblong, obliquely cut into 3–9 oblong or linear and obtuse mostly entire lobes; cup hemispherical-saucer-shaped, rough or tubercled at maturity, naked, much shorter than the ovoid or oblong acorn (1´ long).—All soils, Maine to S. E. Minn., E. Kan., and south to the Gulf. A large and valuable tree; lobes of the leaves short and broad (3–5), or deep and narrow (5–9).
2. Q. stellàta, Wang. (Post Oak. Iron Oak.) Leaves grayish or yellowish-downy underneath, pale and rough above, thickish, sinuately cut into 5–7 rounded divergent lobes, the upper ones much larger and often 1–3-notched; cup deep saucer-shaped, naked, one third or half the length of the ovoid acorn (6–9´´ long). (Q. obtusiloba, Michx.)—Sandy or sterile soil, Martha's Vineyard to Mich. and E. Neb., south to Fla. and Tex.; common, especially southward. A small tree with very durable wood.
3. Q. macrocárpa, Michx. (Bur Oak. Over-cup or Mossy-cup Oak.) Leaves obovate or oblong, lyrately-pinnatifid or deeply sinuate-lobed, or nearly parted, sometimes nearly entire, irregular, downy or pale beneath; the lobes sparingly and obtusely toothed, or the smaller ones entire; cup deep, thick and woody (9´´–2´ across), conspicuously imbricated with hard and thick pointed scales, the upper ones awned, so as usually to make a mossy-fringed border; acorn broadly ovoid (1–1½´ long), half immersed in or entirely enclosed by the cup.—Rich soil, N. Scotia to W. Mass. and Penn., west to Minn., central Neb., and Kan. A large and valuable tree; extremely variable in the size and fringe of the acorns.—Var. olivæfórmis, Gray, is only a narrower-leaved form with unusually small oblong acorns.
4. Q. lyràta, Walt. (Over-cup Oak. Swamp Post Oak.) Leaves crowded at the end of the branchlets, obovate-oblong, acute at base, more or less deeply 7–9-lobed, white-tomentose beneath or at length smoothish, the lobes triangular to oblong, acute or obtuse, entire or sparingly toothed; fruit short-peduncled or sessile; cup round-ovate, thin, with rugged scales, almost covering the depressed-globose acorn (8–10´´long).—River swamps, S. E. Mo. to S. Ind., Tenn., N. C., and southward.—A large tree, with flaky bark; intermediate between n. 3 and n. 5.
[*][*] Leaves coarsely sinuate-toothed, but not lobed (except slightly in n. 5), whitish and more or less downy beneath; cup hoary, hemispherical or a little depressed, about half as long as the oblong-ovoid edible acorn.—Chestnut-Oaks.
5. Q. bícolor, Willd. (Swamp White Oak.) Leaves obovate or oblong-obovate, wedge-shaped at base, coarsely sinuate-crenate and often rather pinnatifid than toothed, usually soft-downy and white-hoary beneath, the main primary veins 6–8 pairs, lax and little prominent; fruiting peduncle much longer than the petiole; upper scales of the cup awn-pointed, sometimes forming a mossy-fringed margin; acorn scarcely 1´ long.—Borders of streams and swamps, S. Maine to Ont., Minn., and E. Kan., and south in the mountains to N. Ga.—A large tree, with flaky bark.
6. Q. Michaùxii, Nutt. (Basket-Oak. Cow-Oak.) Leaves (5–6´ long) oval or obovate, acute, obtuse or even cordate at base, regularly dentate (commonly not deeply), rather rigid, usually very tomentose beneath; stamens usually 10; fruit short-peduncled; cup shallow, tuberculate with hard and stout acute scales, without fringe; acorn 1½´ long. (Q. Prinus, var Michauxii, Chapm.)—Borders of streams and swamps, Del. to Fla., and in the west from S. Ind. to Mo., and south to the Gulf.—A large and valuable tree, with gray flaky bark and large sweet edible acorns. Intermediate forms appear to connect with n. 5, of which Dr. Engelmann considered it a sub-species.