202 Pub. Puget Sound Biol. Sta. Vol. 2, No. 46 



that the rate of development of both swamp and bog in this depression 

 has been limited by the fact that the water runs off rapidly through the 

 gravelly soil. The fact that the area is dry in late summer must have lim- 

 ited the coming in of many plants, and undoubtedly was a factor in the 

 rather slow growth of Sphagnum before it was thoroly shaded by hard- 

 hack. The fact that this depression is flooded in spring and early summer 

 also keeps out a spring flora of any sort except aquatic vegetation, and the 

 fact that it dried up in late summer tends to kill out the aquatic plants. 

 The result has been very slow development of vegetation. There is a well 

 dcvelojaed bog many acres in area only 1.6 kilometers (1 mile) from this 

 depression. While the soil survey shows the same type of soil underlying 

 both the bog and the depression, it is not known what local differences 

 there may be in the soil that may influence the water-holding capacity in 

 these two areas. 



The bogs of the Puget Sound region overlie several different types of 

 soil. Many of them occur on glacial till. In some of these the sphagnum 

 peat lies directly upon the material deposited by glacial action. In other 

 cases a layer of swamp muck lies between the glacial material and the 

 sphagnum peat, indicating that a swamp stage preceded the bog stage. 

 In some cases there is also a layer of inwash material consisting of sand 

 and clay. The following bogs occur on glacial till, little if at all modified 

 by stream action: Green Lake bog, Henry bog, Maltby bog, and Fauntle- 

 roy bog. Turesson (1916) has made a section of the Green Lake bog 

 and finds the following layers: (A) 60 cm. of Sphoc/mim teres peat; (B) 

 15 cm. brownish black mud; (C) 20 cm. Sphac/num palusire peat; (D) 

 .90 cm. forest peat; (E) 150 cm. Carex peat; (F) Clay. 



Other bogs occur on residual soil. The bogs on the prairie in Grays 

 Harbor county are examples of this. Other bogs south of Olympia, Wash- 

 ington, are known to occur on fine sand deposited by glacial streams. 

 Other conditions being equal, development of bogs must undoubtedly be 

 slower on very sandy or gravelly soil than on clay, because water would 

 run away through the soil more rapidly. Undoubtedly some of the bogs 

 near the coast overlie sand that has been deposited by wave action, and in 

 some cases worked over by winds. In no case has the writer found a 

 bog in the Puget Sound region directly overlying rock. The whole sub- 

 ject of the soil underlying the peat deposits of this region needs further 

 investigation. 



The bogs of the Puget Sound region are not typical "raised" bogs 

 such as occur in Newfoundland and some parts of eastern Canada and 

 Maine (Nichols 1918). Our bogs are usually slightly higher in the 

 center than at the margin, but the difference in level is at most 1 meter 

 or less, while in the "raised" bogs such as have been described by Ganong, 



