KATE OF GROWTH IN SPHAGNUM BOGS 731 



(Henry bog). The hemlock is also the pioneer in the advance of the 

 conifers in a large majority of cases, although not in all. The western 

 white pine is the pioneer in a part of the Henry bog, the lodgepole pine 

 in much of the Maltby bog, and the Douglas fir in small portions of the 

 Fauntleroy bog. Hemlock makes up only a very small part of the 

 forest in the neighborhood of the bogs examined, while Douglas fir 

 makes up a very large part, probably 90 per cent in many cases. 



The Douglas fir occurs in only two of the bogs examined (Fauntle- 

 roy and Green Lake). It is the lowest of the five species reported in 

 the ratio of its growth in diameter in bogs to its growth in diameter in 

 other habitats, although in its absolute rate of growth in bogs it is 

 higher than the lodgepole pine and the giant cedar. It is also the low- 

 est of the five species in the ratio of its rate of growth in height in bogs 

 to its rate of growth in height outside of them. Its rate of growth in 

 height in bogs is greater than that of the giant cedar and the western 

 white pine. 



Some data on the growth of Puget Sound conifers under good forest 

 conditions have been found in literature. The data are mainly from 

 older trees than those reported by the writer and are based on a larger 

 number of trees. The measurements and counts were all made at a 

 height of 4.5 feet. It will be noted that comparisons as to the relative 

 rates of growth of the various species in bogs and outside of them, 

 based on the work cited in the following paragraphs, would not in all 

 cases be consistent with those mentioned above. While it thus appears 

 that the data at hand are insufficient for exact conclusions as to rela- 

 tive growth rate of the different species, the general fact of very slow 

 growth in bogs is brought out strikingly. Allen's^ graph indicates that 

 western hemlock in the open grows in diameter at an average annual 

 rate of 4.7 mm. from its twentieth to its fortieth year, while in the 

 shade its rate for the same ages is 2.5 mm. 



Rockwell*' states that the average diameter of 650 specimens of west- 

 ern white pine forty years of age measured was 7.5 inches. This is an 

 average annual growth in diameter of 4.68 mm. In discussing his data 

 he says : "Although in the early seedling stage the growth of the west- 

 ern white pine is comparatively slow, after the young tree becomes 

 thoroughly established it is one of the most rapid growers of the for- 

 est. . . . These figures are for average soils." The writer's meas- 

 urements of the growth of this species were all made near Silverdale, 

 Washington, on specimens growing on hills in very dry, stony soil. 



° Allen, E. T. : "The western hemlock." Bull. 33, U. S. Bur. For., 1902. 

 ' Rockwell, F. I. : "White pine in four Northwestern States." West Coast 

 Lumberman, Oct. i, 1916, p. 20. 



