50 



BULLETIN 343, U. S. DEPARTMENT OF AGRICULTURE. 



The aspen fibers (shown in PL V) appear to be even shorter than 

 those of the birch. The steamed pulp when run into a 63-pound 

 sheet gave a Mullen test of 0.51 point per pound and 6.2 points per 

 thousandth ineh of thickness. 



Between the cooked and uncooked hemlock fibers (shown in PL VI) 

 there is more contrast in respect to length than in the case of birch 

 and poplar. The cooked hemlock when run into a 55-pound sheet 

 without sulphite gave a Mullen test of 0.51 point per pound and 6 

 points per thousandth inch of thickness. 



Both the steamed and unsteamed jack pine (shown in PL VII) 

 are remarkably free from wood flour and short fiber. The steamed- 



Fig. 38.— White pine (Pinus strobus). 



wood sample, when run into a 43-pound sheet without sulphite, gave 

 a Mullen test of 0.47 point per pound and 4.5 points per thousandth 

 inch of thickness. 



In Plate VIII, which shows steamed and unsteamed tamarack 

 fibers, the much greater length of the former is apparent. 



Plates IV, VI to X, and XII, figure 1, show the fibers from a 

 number of different woods ground in the natural state under the 

 same conditions. With the exception of western larch, the fibers 

 are of very good quality and compare well with those of spruce. So 

 far as length and fineness go, the fibers shown in Plates VII, X, and 

 XII are fully equal to spruce. 



