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 b.u.t.tERNUT.
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.
_a."_ Pores crowded, occupying nearly all the s.p.a.ce between pith rays.
_a.""_ Color yellowish white, often with a greenish tinge in heart-wood ........................TULIP POPLAR.
CUc.u.mBER TREE.
_b.""_ Color of sap-wood grayish, of heart-wood light to dark reddish brown ......................SWEET GUM.
_b."_ Pores not crowded, occupying not over one-third the s.p.a.ce between pith rays; heart-wood brownish white to very light brown .........................Ba.s.sWOOD.
_b._ Pith rays scarcely distinct, yet if viewed with ordinary magnifier, plainly visible.
_a."_ Pores indistinct to the naked eye.
_a."_ Color uniform pale yellow; pith rays not conspicuous even on the radial section .....BUCKEYE.
_b."_ Sap-wood yellowish gray, heart-wood grayish brown; pith rays conspicuous on the radial section.
SOUR GUM.
_b."_ Pores scarcely distinct, but mostly visible as grayish specks on the cross-section; sap-wood whitish, heart-wood reddish ..............................BIRCH.
D. Pith rays not visible or else indistinct, even if viewed with magnifier.
1. Wood very soft, white, or in shades of brown, usually with a silky l.u.s.ter .................................COTTONWOOD (POPLAR).
ADDITIONAL NOTES FOR DISTINCTIONS IN THE GROUP.
Cherry and birch are sometimes confounded, the high pith rays on the cherry on radial sections readily distinguishes it; distinct pores on birch and spring wood zone in cherry as well as the darker vinous-brown color of the latter will prove helpful.
Two groups of birches can be readily distinguished, tho specific distinction is not always possible.
1. Pith rays fairly distinct, the pores rather few and not more abundant in the spring wood: wood heavy, usually darker, CHERRY BIRCH and YELLOW BIRCH.
2. Pith rays barely distinct, pores more numerous and commonly forming a more porous spring wood zone; wood of medium weight, CANOE OR PAPER BIRCH.
[Ill.u.s.tration: Fig. 136. Wood of Beech, Sycamore and Birch.]
The species of maple may be distinguished as follows:
1. Most of the pith rays broader than the pores and very conspicuous ........................................SUGAR MAPLE.
2. Pith rays not or rarely broader than the pores, fine but conspicuous.
_a._ Wood heavy and hard, usually of darker reddish color and commonly spotted on cross-section ...............RED MAPLE.
_b._ Wood of medium weight and hardness, usually light colored.
SILVER MAPLE.
[Ill.u.s.tration: Fig. 137. Wood of Maple.]
Red maple is not always safely distinguished from soft maple. In box elder the pores are finer and more numerous than in soft maple. The various species of elm may be distinguished as follows:
1. Pores of spring wood form a broad band of several rows; easy splitting, dark brown heart ............................RED ELM.
2. Pores of spring wood usually in a single row, or nearly so.
_a._ Pores of spring wood large, conspicuously so WHITE ELM.