1919 ' ^^99' ^^ ^^9 Succession 207 



trees are found in the bog very close to the lake margin. One spruce tree 

 (Picea sitchensis) approximately 30 cm. (1 foot) in diameter was found 

 less than 1 meter from the open water of the lake. The cause of this 

 practically static condition of the bog margin was not determined. 



The bogs around Mud lake, prior to the lowering of the lake by 

 drainage in 1916, furnished illustrations of both of the above types of 

 the filling of lakes by the advance of Sphagnum. Where Labrador tea, 

 swamp laurel and cranberry were pioneers in bog advance, the peat bog 

 birch {Betula glandulosa) was commonly associated with them. The 

 water here was not nearly so deep at the advancing margin of the bog as 

 it is at Crystal lake. This birch sometimes grows to a height of 4.1 

 meters (15 feet) and its stems are much stouter than those of Labrador 

 tea and swamp laurel, and thus furnish a much stronger support for the 

 advancing Sphagnum. This species is not confined to the situation just 

 described. It occurs commonly in various moist habitats around advanc- 

 ing bogs, both around the Mud lake bogs and several other bogs, notably 

 those at Cottage lake in King county, and at Milton in Pierce county. The 

 situation at Mud lake described above is the only one seen by the writer, 

 however, in which it is a factor in the advance of Sphagnum upon open 

 water. Smaller specimens of it are sometimes found in a fairly mature 

 stage of the bog but it does not seem to flourish well there. The evidence, 

 so far as the writer has seen it, seems to indicate that this species belongs 

 in the succession preceding the bog and neither in the bog succession itself 

 nor in forest stage which succeeds it. 



On the south side of Mud lake the conditions were somewhat similar 

 to those around the bog lake at Sunnydale described above. Purple marsh- 

 locks functioned in somewhat the same way in both cases. In some cases 

 in the Mud lake region it was preceded by water lilies, but in other cases 

 the shallow margin of the lake was being filled by a dense growth of the 

 rhizomes of the buck bean {Menyanthes trifoliata) , and at a later stage 

 Sphagnum was advancing upon this by the aid of the purple marshlocks. 

 This plant was also found as a pioneer in the advance of the bog upon 

 Echo lake before conditions were changed there by improvements. 



In several bogs, notably those at Mud lake and Sunnydale, the water 

 lily was found in the same sort of pits as those in which the skunk cabbage 

 is found. Like the latter plant, it has large leaves, and it seems probable 

 that it has survived from the lake stage much as the other has from the 

 swamp stage. The common presence of these two species in our bogs 

 furnishes ready evidence as to the plant successions that have preceded 

 the bog stage. 



