4(3). Mature acorns nearly enclosed in the cups, the orifice usually less than 

 half the diameter of the acorn; petioles to 2 cm. long, sparsely 

 pubescent 2. Q. lyrata. 



4. Mature acorns rarely more than half-enclosed in the cups, with orifice as 



great as the diameter of the acorn; petioles 1 cm. long or less, 

 gray-puberulent to velvety-tomentulose 3. Q. similis. 



5(2). Mature leaves with a rounded to broadly cuneate base, cinereous-tomentu- 

 lose beneath 4. Q. falcata. 



5. Mature leaves with a subtruncate base, glabrous beneath except for tufts of 



hair in the vein axils 5. Q. palustris. 



6(1). Leaves narrowly elliptic to linear-lanceolate, fully 5 times as long as 

 broad, markedly revolute and awl-shaped upon issuing from the 

 buds 6. Q. Phellos. 



6. Leaves elliptic to oblanceolate or clavate, scarcely more than 3 times as long 



as broad, flat when issuing from the buds, never awl-shaped (7) 



7(6). Leaves typically narrowly oblong to oblanceolate, glossy beneath 



7. Q. laurifolia. 



7. Leaves typically cuneiform to clavate or broadly obovate, occasionally shal- 



lowly 3-lobed at apex, dull green beneath 8. Q. nigra. 



1. Quercus macrocarpa Michx. Bur oak. 



Large trees; twigs very coarse, 3-5 mm. thick or rarely somewhat more slender, 

 fluted, yellowish or gray, from villous to pubescent or both becoming glabrate, 

 with few very inconspicuous lenticels; buds 4-5 mm. long, ovoid or narrowly so, 

 obtuse to acute, grayish-brown, sparsely pubescent to tomentose; stipules per- 

 sistent or sometimes deciduous, about 1 cm. long, awl-shaped or the lateral ones 

 longer and obviously spatulate-dilated, the terminal ones coarsely thickened and 

 gray-tomentose; leaves deciduous, rather thin, to 20 cm. long and 15 cm. broad, 

 obovate in oufline, the apices broadly rounded, the bases rounded to cuneate, 

 rather deeply incised, with 3 or 4 sinuses on each side, these acute or narrowly 

 rounded, usually reaching nearly to the midrib (especially below), the lobes 

 clavate, undulate distally, the basal ones often much-shortened, margins minutely 

 revolute, upper surfaces glabrate, dull or slightly lustrous, lower surfaces villous 

 and gray-puberulent with a mixture of long spreading and short appressed stellate 

 hairs or the appressed hairs rarely absent and the surface then green; petioles 

 to 25 mm. long, densely or sparsely pubescent; staminate catkins 3-4 cm. long, 

 the rachis yellow-tomentose, at length rather loosely flowered, the perianth deeply 

 incised with narrow oblong lobes, the anthers scarcely exserted; pistillate catkins 

 about 2 cm. long, about 4-flowered near the end; fruit annual, solitary or paired 

 on a peduncle 1-2 cm. long and 2-3 mm. thick; cups 3-6 cm. broad, 2-5 cm. 

 deep, moderately or deeply cup-shaped, margins woolly with attenuate apices of 

 the uppermost scales, these sometimes closing the orifice of the cup; cup scales 

 broad-based, the apices of the basal scales not elongate, the dorsal surface keeled 

 (thickened), the bases broad, often appearing to be fused to adjacent scales, the 

 whole gray-pubescent; acorns 3-5 cm. long, 2-4 cm. broad, ovoid, broadly 

 rounded, usually one half or three fourths included, sometimes wholly or only 

 one fourth included. 



In moist forests along streams and bottomlands in e. Okla. and e. and cen. 

 Tex.; e. to the Atl. and n. to N.B. and Sask. 



2. Quercus lyrata Walt. Overcup oak, swamp post-oak. 



Moderate trees; twigs rather coarse, to 4 mm. thick, finely fluted, from minutely 

 villous becoming glabrate and gray or yellowish with few inconspicuous lenticels; 

 buds about 3 mm. long, ovoid, obtuse, gray-puberulent; stipules tardily deciduous 



784 



