THE TIMBERS OF COMMERCE 



wheels especially the hubs, in cooperage and ship-building " (49). 

 " Less valuable than the Rock Elm, durable when not exposed, 

 . . . twists, shrinks much, warps . . . will take nails" (95). 

 " Difficult to split . . . wheel-stock, saddle-trees, flooring, boats " 

 (100). " To about 100 ft. high by 6 ft. diam. . . . tough . . . 

 sheaves, gunwales, coffins . . . will withstand the driving of 

 bolts . . . strong but not durable" (65). 



Authorities. Hough (49), pt. ii. p. 22. Stevenson (113), p. 39. 

 Laslett (60), p. 177. Sargent (100), No. 224. C. Robb (95), 

 Macoun (65), p. 23. Wiesner (131), L. 6, p. 66. 



Colour. Heart-wood light brown. Sap-wood yellowish white. 



Anatomical Characters. Transverse section. (Compare U. 

 Campestris, No. 172). 



Pores. Clear from their masses not from their size (between 

 i and 1-2). Nearly twice as long as broad, about 7 per sq. mm. : 

 the remainder of the ring occupied by small, closely packed 

 pores, size 3-4, in long wavy lines or festoons. These decrease 

 perceptibly in size right up to the Autumn boundary, where 

 they are about 160 per sq. mm. 



Rays. Just visible, size 4, numerous, 6-8 per mm. : straight, 

 not avoiding the pores : brown. 



Rings. My specimen has 12 rings per inch. No contrast in 

 colour. 



Pith. ? 



Radial Section. Much lighter in shade than the Transverse 

 section: pores prominent and coarse though colourless lines: 

 rays minute, dull-browTi or whitish flakes : rings fairly evident 

 as the pores of the pore-ring are regularly exposed. 



Tangential Section. As the Radial, but the pores are much 

 finer than in that section. The rings show as prominent lines 

 and fringed loops of open pores. Other details as No. 171. 



Type specimens from commercial sources, unauthenticated 

 but reputed to be this species. ? 



No. 174. ROCK ELM. Ulmus racemosa. D. Thomas. 

 PLATE XII. FiG..io8. 



Natural Order. Urticaceae. 



Alternative Names. American Elm. Swamp Elm : Cliff Elm : 

 Cork Elm : White Elm : Trauben Ulme : Orme a grappes : Olmo 

 de Corcho (49). 



Sources of Supply. North America : United States and Canada. 



Physical Characters, etc. As Ulmus americana except : Re- 

 corded dry-weight 43-45* Ibs. per cu. ft. 



Grain. Very fine and close. Surface bright : feels like cane, 

 and has a similar appearance in some sections. 



198 



