=7.= =Quercus macrocàrpa= Michaux. Bur Oak. Plate 46. Large trees; branchlets of young trees generally develop corky wings which are usually absent on mature trees; leaves on petioles 1-2 cm. long, obovate in outline, generally 1-2.5 dm. long, the margins more or less deeply cut so that there are usually 7 lobes, sometimes only 5, or as many as 9 or 11, sometimes the sinuses extend to the midrib, giving the leaf a "skeleton" appearance, the lobes are very irregular in shape and variously arranged, but often appear as if in pairs, lobes rounded and ascending, the larger lobes are sometimes somewhat lobed, the three terminal lobes are usually the largest and considered as a whole would equal in size one half or more of the entire leaf area, the base of the leaf is wedge-shape or narrowly rounded; leaves at maturity are dark green and smooth above, or somewhat pubescent along the midrib, a gray-green and woolly pubescent beneath; acorns usually solitary, sometimes in pairs or clusters of three, sessile or on short stalks, sometimes on stalks as long as 2.5 cm.; nuts very variable in size and shape, ovoid to oblong, often very much depressed at the apex, 2-3 cm. long, enclosed from 1/3 to almost their entire length in the cup which is fringed at the top; cups thick and large, sometimes 4.5 cm. in diameter; scales tomentose on the back and somewhat tuberculate, blunt near the base of the cup, but at and near the top of the cup they become long attenuate and on some trees appear almost bristle like; kernel sweet. =Distribution.=--Nova Scotia to Manitoba, south to Georgia and west to Texas and Wyoming. Found in all parts of Indiana, although we have no reports from the knob area where no doubt it is only local. It is a tree of wet woods, low borders of streams, etc., except among the hills of southern Indiana, it is an occasional tree of the slopes. In favorable habitats it was a frequent to a common tree. Its most constant associates are white elm, swamp white and red oak, linn, green and black ash, shellbark hickory, etc. It is sometimes called mossy-cup oak. =Remarks.=--Wood and uses similar to that of white oak. In point of number, size and value it ranks as one of the most valuable trees of the State. Michaux[39] says: "A tree three miles from Troy, Ohio, was measured that was fourteen feet and nine inches in diameter six feet above the ground. The trunk rises about fifty feet without limbs, and with scarcely a perceptible diminution in size." =7a.= =Quercus macrocarpa= var. =olivæfórmis= (Michaux filius) Gray. This variety is distinguished from the typical form by its shallow cup, and the long oval nut which is often 3 cm. long. The cup is semi-hemispheric, and encloses the nut for about one-half its length. Authentic specimens are at hand from Wells County, and it has been reported from Gibson and Hamilton Counties. No doubt this form has a wider range.