BOTANICAL ASPECTS OF PAPER-PULP AND TANNING INDUSTRIES 515 



cornstalks, bamboo, and cane, they concentrated on non-resinous woods, par- 

 ticularly poplar, hemlock, and white wood. This chemical process, it is to be 

 noted, antedated Pagenstecher's setup by about thirteen years. 



In the year that Pagenstecher began his mechanical groundwood operations, 

 a second chemical technique, the sulfite process, was patented in the United 

 States by B. C. Tilghman, who had begun experiments in France. And in 

 1884 a German patent was granted to C. F. Dahl in Germany on his develop- 

 ment of the sulfate process. 



These three chemical processes for pulping wood — soda, sulfite, sulfate — 

 and mechanical grinding to obtain groundwood pulp are still the processes in 

 use today, with modern improvements, to be sure, and their initiation in the 

 mid-nineteenth century paved the way for the tremendous increase that has 

 since transpired in the industrial utilization of wood fibers throughout the 

 world in the manufacture of paper. 



Woods other than basswood and aspen undoubtedly were utilized by the 

 pioneer wood-pulp manufacturers, but these two were preferred because of 

 their resin-free nature and other inherent qualities that make them suitable 

 for pulping. It was not long, however, before attention became focused on 

 spruce, two species of which grew in abundant quantities in the northeastern 

 States and eastern Canada, with a close relative on the Pacific Coast. For 

 many years the first two of these, eastern red spruce (Picca rubens) and 

 eastern white spruce {P. canadensis), particularly the former, were the Ameri- 

 can woods par excellence for pulping; and as the great stands of timber in 

 the Pacific Northwest later became exploited, Sitka spruce {P. sitchensis) 

 joined them. 



The preeminence of spruce as pulpwood until the very end of the fourth 

 decade in the twentieth century was a result, primarily, of its long (3 mm.) 

 strong fibers (tracheids in anatomical terminology), comparatively free from 

 resins, gums, tannins, and other components objectionable in other woods; 

 of its light color, general soundness, and fair freedom from knots, rot, and 

 other defects; and of the high cellulose content of the fibers, easily separated 

 from other substances. In addition, it was available in ample and accessible 

 quantities, and pulping techniques to use resinous woods profitably were not 

 developed until the 1920's. 



In 1899 spruce attained a high of 76 per cent among all pulpwoods in the 

 United States. It continued long thereafter to be the leader, reaching a quanti- 

 tative peak of nearly 314 million cords in 1920. During the intervening two 

 decades, however, its percentagewise preeminence declined to 60 per cent 

 by 1916, and then to 23 per cent in 1939. 



In 1916 at least 15 other native woods supplied the pulp mills. Eastern 

 hemlock {Tsuga canadensis) was second — 14 per cent; poplar, consisting of 

 the two aspens {Populus grandidentata, P. tremuloides) , was third — 8 per 

 cent. The remaining 16 per cent consisted, for the most part and in descend- 



