In the oaks, two groups can be readily distinguished by the manner in which the pores are distributed in the summer wood. (Fig. 133.) In the white oaks the pores are very fine and numerous and crowded in the outer part of the summer wood, while in the black or red oaks the pores are larger, few in number, and mostly isolated. The live oaks, as far as structure is concerned, belong to the black oaks, but are much less porous, and are exceedingly heavy and hard. [Illustration: Fig. 133. Wood of Red Oak. (For white oak see fig. 129, p. 291.)] [Illustration: Fig. 134. Wood of Chestnut.] [Illustration: Fig. 135. Wood of Hickory.] ==== III.--DIFFUSE-POROUS WOODS. (A few indistinctly ring-porous woods of Group II, D, and cedar elm may seem to belong here.) A. Pores varying in size from large to minute; largest in spring wood, thereby giving sometimes the appearance of a ring-porous arrangement. 1. Heavy and hard; color of heart-wood (especially on longitudinal section) chocolate brown ..........................BLACK WALNUT. 2. Light and soft; color of heart-wood light reddish brown BUTTERNUT. B. Pores all minute and indistinct; most numerous in spring wood, giving rise to a lighter colored zone or line (especially on longitudinal section), thereby appearing sometimes ring-porous; wood hard, heart-wood vinous reddish; pith rays very fine, but very distinct. (See also the sometimes indistinct ring-porous cedar elm, and occasionally winged elm, which are readily distinguished by the concentric wavy lines of pores in the summer wood) .........CHERRY. C. Pores minute or indistinct, neither conspicuously larger nor more numerous in the spring wood and evenly distributed. 1. Broad pith rays present. _a._ All or most pith rays broad, numerous, and crowded, especially on tangential sections, medium heavy and hard, difficult to split. ................................SYCAMORE. _b._ Only part of the pith rays broad. _a.'_ Broad pith rays well defined, quite numerous; wood reddish white to reddish ....................BEECH. _b.'_ Broad pith rays not sharply defined, made up of many small rays, not numerous. Stem furrowed, and therefore the periphery of section, and with it the annual rings sinuous, bending in and out, and the large pith rays generally limited to the furrows or concave portions. Wood white, not reddish .....................BLUE BEECH. 2. No broad pith rays present. _a._ Pith rays small to very small, but quite distinct. _a.'_ Wood hard. _a."_ Color reddish white, with dark reddish tinge in outer summer wood ...........................MAPLE. _b."_ Color white, without reddish tinge ...........HOLLY. _b.'_ Wood soft to very soft.