190 PLANT KELATIONS. 



decay is checked. As a consequence, the sphagnum-moor 

 waters are strongly antiseptic; that is, they prevent decay 

 by excluding certain bacteria. It is a well-known fact that 

 bodies of men and animals which 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 types of moors, therefore, may be contrasted 

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

 characterized chiefly by grassy plants ; the sphagnum-moor 

 is poor in food material, and is characterized chiefly by 

 sphagnum moss. It will be noted that peat may be formed 

 in connection with both of these moors, but in the swamp- 

 moor 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-moor, also, 

 yields a great amount of ash, for the swamp-moor 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-moor 

 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. 165). 

 The larch is a very common swamp tree of the northern 

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

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

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



