90 ECONOMIC WOODS OF THE UNITED STATES 



b 4 Bands of small pores in late wood numerous, 

 wider than intervening spaces, often very wavy 

 and branched. Growth rings not always dis- 

 tinct. Wood cross-grained, difficult to split. 

 Winged Elm, U. alata Michx. (S, C); Cedar 

 Elm, U. crassifolia Nutt. (S). 



b 1 Pores in late wood variable in size from fairly large to 

 minute, clustered, associated with parenchyma which 

 often is confluent into tangential bands irregular and 

 broken or more or less continuous in outer portion of 

 wide rings. 



a 2 Woods hard and heavy. Odorless. Color pro- 

 nounced. Tyloses present or absent. Rays fine 

 but distinct. 



a 3 Tyloses present, light-colored ; gum deposits absent 

 or only occasional. 



a 4 Wood decidedly variable in density but not 

 horn-like; sp. gr. .55-.G5. Color orange-yellow 

 to yellowish-brown, not uniform; becoming 

 russet-brown upon exposure. Pores only par- 

 tially filled with tyloses. Band of pores in early 

 wood varying from narrow to broad. Rays 

 very conspicuous on radial surface. Small ves- 

 sels with spirals; perforations simple; pits into ray cells 

 simple or half-bordered. Rays heterogeneous. Red 

 Mulberry, Morus rubra L, (C, S). (Plate V, 

 Fig. 1); White Mulberry, M. alba L., (Int.). 



b 4 Woods extremely hard, like horn; sp. gr. .77-.S4. 

 Color of freshly exposed wood mostly yellow 

 (see below) . All pores of heartwood completely 

 filled with tyloses. Band of pores in early 

 wood narrow. Rays not conspicuous on radial 

 surface. Small vessels with spirals; perforations simple; 

 pits into ray cells simple or half-bordered. Rays more 

 or less heterogeneous, or with considerable irregularity 

 in the shape of the cells. 



a 5 Color of freshly exposed wood golden yellow, 

 becoming orange-brown upon exposure to 

 sunlight; usually with rather distinct reddish 



