106 ECONOMIC WOODS OF THE UNITED STATES 



a 4 Pores rarely in radial groups. Cojoxjvidely 

 variable, depending upon age of tree and locality 

 of growth, from clear yellow to green, brown or 

 purplish; sapwood often variegated or striped, 

 light gray ornearly white. Curly and mottled 

 grain not uncommon. Sp. gr. .38-.48, average 

 .42. Vessels with round or elliptical bordered pits in 

 rows, sometimes scalariform in part; without spirals; 

 perforations scalariform with few bars. Rays mostly 

 3-seriate, few to 60, mostly 20--40, cells high. Poplar, 

 Yellow Poplar, Tulip-tree, Whitewood. Lirio- 

 dendron tulipifera L. (C. N). (Plate VI, Figs. 

 2, 4). 60 

 b 4 Pores often in radial groups of 3-8. Vessels with 

 scalariform bordered pits (Plate VI, Fig. 3); spirals in- 

 distinct. 



a 5 Color mostly yellow or greenish; often closely 

 x resembling IAriodendron. Sp. gr. .42-54, 

 average .47. Vessel perforations usually simple. 

 Rays homogeneous; mostly 2-seriate and 10-15 cells 

 high. Cucumber Tree, Magnolia acuminata 

 L. (C, A). 

 b 5 Color light brown. Sp. gr. about .50. Vessel 

 perforations scalariform with few bars. Rays hete- 

 rogeneous; 2-4 cells wide, mostly 50-100 cells high. 

 White or Sweet Bay, M. glauca L. (S). 

 b 3 Wood parenchyma not visible with lens. Wood 

 elements, except rays, in storied arrangement, 

 producing somewhat indistinct "ripple marks " on 

 tangential surface; 55-60 per inch. Wood light, 

 soft, compact, moderately strong; sp. gr. .38-52, 

 mostly between .40-. 45. Color light brown to 

 creamy white. Rays of two general sizes: (1) uniseriate 

 and 10-15 cells high; (2) 3-5 cells wide and 50-100 cells 

 high; mostly homogeneous. Vessels with spirals; tyloses 

 absent; perforations simple; bordered pits not scalariform; 

 pits into ray cells small, half-bordered. Wood parenchyma 

 in numerous fine tangential lines. Basswood, Lin, Tilia 

 americana L. (N, C); T. pubescens Ait. (S, C)-, 

 T. heterophylla Vent. (A, C, S). 61 



