94 ECONOMIC WOODS OF THE UNITED STATES 



large, not abundant, usually in very irregular zone; in narrow 

 growth rings rather diffuse. Rays fairly uniform, _ not con- 

 spicuous , abundant. Wood parenchyma m bne tangential 

 lines. 



a Wood elements in tier-like arrangement (Plate IV, Figs. 4, 

 5), producing on longitudinal surface fine, wavy cross- 

 markings readily visible to unaided eye. Lines of wood 

 parenchyma indistinct, finer than the rays (Plate IV, 

 Fig. 2). Crystals present, rather small; mostly in long 

 rows. Rays in stories; fairly uniform in height; 1-2 

 (rarely 3) seriate; cells large (Plate IV, Fig. 4). Color of 

 wood of old trees dark brown to black; thick sapwood 

 (making up all or nearly all of young trees) yellowish, 

 usually streaked with black. Wood fibres thick-walled. 

 Wood very heavy, hard, and strong. Tyloses absent. 

 Persimmon. Diospyros virginiana L. (S, C). 



b Wood elements not in tier-like arrangement. Lines of 

 wood parenchyma as distinct as the rays. Crystals large; 

 usually solitary. Rays irregularly disposed; not uniform 

 in height or shape; ■ 1-5 seriarte; pells small (Plate IV, 

 Fig. 3). Qolor of wood brown to re ddish bTown ; thick 

 sapwood white, often with dark reddish streaks. Tyloses 

 present. Hickory.'** 



a^ Wood very hard, heavv. torup;h. strong, resilient .-. Wood 

 fibres very thick-walled. Shagbark. Hicoria ovata Brit. 

 (C, N) (Plate IV, Fig. 3); SheUbark. ladniosa Safg. 

 (C) ; Mocker Nut. alba Brit. (C, N,- S) ; Pignut, glabra 

 Brit. (C, N,S). 



b' Wood hard, heavy, brittle, fairly strong. Wood fibres 

 comparatively thin-walled. 



a^ Growth rings not clearly defined. Large pores not 

 in well-defined zone; scattered; approaching diffuse- 

 porous. Water Hickory. H. aquatica Brit. (S). 



b^ Growth rings clearly defined. Large pores in fairly 

 well-defined zone, 1-several pores wide. Pecan. 

 H. pecan Brit. (S, C) ; Nutmeg Hickory, myristicce- 

 formis Brit. (S); Bittemut. minima Brit. (C, N, S). 



B Diffuse-porous Woods. Pores numerous; usually not prom- 

 inent on cross section; diffused throughout growth ring instead 



V 



