146 American Midland Naturalist Monograph No. 7 



Oak. [Q. borealis Michx.f. ; Q. borealis var. maxima 



(Marsh.) Ashe] Q. rubra L. 



6. Leaves usually cleft more than halfway to the midvein. 



7. Acorn-cup shallow, saucer-shaped, enclosing not more 



than one-third of the acorn; inner bark gray or 



reddish; winter-buds glabrous or sparsely pubescent. 



8. Acorn-cup 1-1.5 cm in diameter, the rim only 3-4 



mm high; acorn 1-1.5 cm long; woods along 



streams. Pin Oak Q. palustris Muench. 



8. Acorn-cup 16-22 mm in diameter, the rim 5 mm or 



more high; acorn 1.8-2.5 cm long; woods near 

 streams, in the s. half of 111. [Q. schneckii Britt.] 



Q. shumardii Buckl. 



7. Acorn-cup hemispherical or tin-binate, enclosing about 

 one-half of the mature acorn. 



9. Scales of the acorn-cup closely appressed; winter- 



buds conical, sparsely pubescent to glabrous. 



10. Acorn-cup 15-25 mm in diameter, the scales 



glabrate, glossy; acorn ovoid; inner bark 



reddish or gray; upland woods, s. 111., rare; 



Jackson, Pulaski, Richland, Union, Wabash, 



and White counties. Scarlet Oak 



Q. coccinea Muench. 



10. Acorn-cup 10-15 mm in diameter, the scales 

 puberulent; acorn ellipsoid; inner bark yel- 

 lowish; upland woods; n. 111., s. to La Salle 

 and Iroquois counties. Northern Pin Oak. 



Hill's Oak Q. ellipsoidalis E.J.Hill 



9. Scales of the acorn-cup pubescent, loosely imbri- 

 cated, the upper forming a fringed border; cup 

 18-25 mm in diameter; winter-buds large, angu- 

 lar, grayish-pubescent; inner bark yellowish or 



orange, upland woods, common. Black Oak 



Q. velutina Lam. 



3. Leaf-lobes not bristle-tipped; acorns maturing in the autumn of 

 the first year. 



11. Leaves irregularly deeply lobed, often somewhat lyrate. 



(White Oaks.) 



12. Mature leaves usually glabrous and glaucous beneath; 

 winter-buds nearly or quite glabrous; acorns 1.5-2 cm 

 long, 3-4 times the length of the shallow cup; upland 

 woods, common. White Oak Q. alba L. 



12. Mature leaves pubescent beneath; acorn-cup one-half to 

 one-third the length of the acorn; buds ovoid, 

 pubescent. 



13. Young twigs pubescent; lower surface of leaves gray- 

 ish or brownish stellate-pubescent; mature acorns 



