190 PLANT KELATIONS. 



for the carnivorous habit and for the sphagnum mosses. 

 Of course it would also account to a certain extent for the 

 exclusion of the characteristic swamp plants. It is a well- 

 known fact that bodies of men and animals that have 

 become submerged in sphagnum-bogs may not decay, but 

 have been found preserved after a very long period. This 

 will also indicate why such bogs are especially favorable for 

 peat formation. 



These two associations, therefore, may be contrasted as 

 follows : The swamp is rich in plant food, and is character- 

 ized chiefly by grassy plants ; the sphagnum-moor is poor 

 in food material and unfavorable to absorption, and is char- 

 acterized chiefly by sphagnum moss. It will be noted that 

 peat may be formed in connection with both, but in the 

 swamp the plant forms cannot be distinguished in the peat, 

 as they have been more or less disorganized through decay, 

 while in the peat of the sphagnum-moor the plant forms 

 are well preserved. The peat of the swamp, also, yields a 

 great amount of ash, for the swamp is rich in soil materials, 

 while the peat of the sphagnum-moor yields very little ash. 

 141. Swamp-forests.— It was noted that the special 

 types of shrub or tree growth associated with the swamp 

 conditions are willows, alders, birches, etc. In the same 

 way there is a peculiar tree type associated with the 

 sphagnum-moor. It is very common to have a sphagnum 

 area occupied by trees, and the area becomes a swamp 

 forest, rather than a sphagnum-moor. The chief tree 

 type which occupies such conditions is the conifer type, 

 popularly known as the evergreens. The swamp forests, 

 therefore, with a sphagnum-moor foundation, are made up 

 of larches, certain hemlocks and pines, junipers, etc., and 

 towards the south the cypress comes in (see Fig. 1G5). 

 The larch is a very common swamp tree of the northern 

 regions, where such an area is commonly called a " tama- 

 rack swamp " (see Fig. 158). The larch forests are apt to 

 be in the form of small patches, while the larger swamp 



