104 



FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



2. Pores in the summer wood not united into lines, or rarely so. 



a. Heart wood reddish brown and very firm Bed ash. 



b. Heartwood grayish brown, and much moi*e porous Black ash. 



In the oaks, two groups can be readily distinguished by the manner in which the pores are distributed in the 

 summer wood. In the white oaks the pores are veiy 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. 



III. DlFFUSE-POKOUS WOODS. 



[A few indistinctly ring poious -woods of Group II, D, and cedar elm may seem to belong heie.] 



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 heartwood (especially on longitudinal section) chocolate brown Black walnut. 



2. Light and soft ; color of heartwood 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, heartwood 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. 



Pig. 11 — Wood of hickory. 



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 . 



}>'. Broad pith rays not sharply defined, made up of many small rays, not numerous. Stem fur- 

 rowed, and therefore the periphery of section, and with it the annual rings, sinuous, bending in 

 and out, and the large pith 1 ays generally limited to the furrows or concave portions. Wood wliite, 

 not reddish Blue beech. 



2. No broad pith rays present. 



a. Pith rays small to very small, hut 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 1 . Wood soft to very soft. 



a". Pores crowded, occupying nearly all the space between pith rays. 



a'". Color yellowish white, often with a greenish tinge in heartwood Tulip poplar, 



Cucumber tree. 



b">. Color of sapwood grayish, of heartwood light to dark reddish brown Sxteet gum. 



b". Pores not crowded, occupying not over one-third the space between pith rays; heartwood 



brownish, white to very light brown Bawwood. 



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. 



I". Sapwood yellowish gray, heartwood grayish brown; pith rays conspicuous on the radial sec- 



„ „ ti0n Sour gum 



I . Pores scarcely distinct, bnt mostly visible as grayish specks on the cross section; sapwood whit- 

 ish, heartwood reddish „ , _ w Birch, 



