RATE OF GROWTH IN SPHAGNUM BOGS 733 



sizes the fact that these conifers, even when growing under the most 

 unfavorable conditions, outside of bogs grow considerably more rapidly 

 than they do in the bogs. The ratio of the growth in diameter under 

 the conditions observed by the forestry workers to that observed by 

 the writer, in bogs, is as follows for the species compared : 



Western hemlock 0.87 



Western white pine 166 



Lodgepole pine 163 



Douglas fir 091 



Very small specimens of the conifers fruit in the bogs. In the 

 Maltby bog the lodgepole pine is commonly found bearing apparently 

 perfect cones when not over i meter (39 inches) tall. The bog trees 

 are, however, all erect, none being prostrated by the bog conditions. 

 They seem to have good anchorage in the substratum of the bog. Of 

 course, the gradual addition to the surface of the bog due to the growth 

 of the sphagnum tends to bury the base of the tree, but this accumula- 

 tion of material is slow. Two specimens of lodgepole pine in the 

 Maltby bog were dug up and the level at which the growth of the tree 

 from the seed had begun was found to be quite evident. The evidence 

 from the two cases seemed to be that the addition of surface material 

 had been at the rate of less than i centimeter (0.4 inch) per year. The 

 roots, however, had penetrated to a considerable depth — deeper than 

 they do in ordinary soil in the same region. That the anchorage is 

 secure is indicated by the fact that the writer has never found a tree 

 blown over in a bog, although trees of the same species and of similar 

 size are frequently found overturned when growing in the open in 

 ordinary soil. 



The most dense growth of trees seen by the writer in any undrained 

 bog of the region is in the Maltby bog. There is scarcely any place 

 where the distance from one specimen to another measures 5 m. (16 

 feet), and in many places there are as many as ten small trees growing 

 in one square meter (11 square feet) of sphagnum. The bog is ad- 

 vancing upon an open lake in its center and the trees are only a few 

 meters back from this lake. The ordinary bog flora (Labrador tea, 

 swamp laurel, cranberry, sundew (Drosera rotundifolia L.), and 

 Sphagnum sp.) persists, however, even where the trees are most 

 crowded. 



The dominant tree in the invasion is, as mentioned above, the lodge- 

 pole pine. In general, the trees are very small, although some speci- 

 mens reach a height of 4 meters (13 feet). There are many specimens 

 only a few centimeters high. The smallest ones found were only 7 cm. 



