336 A TEXT-BOOK OP BOTANY 



to swamp thickets, is a very natural one, each one often 

 passing gradually into the next. 



197. Peat -bogs. This is a peculiar kind of swamp 

 association, characterized by the abundant growth of the 

 bog- or peat-moss, and developed in undrained swamps. 

 Growing out of the springy moss turf there are numerous 

 peculiar plants, such as heaths (Fig. 305) and orchids, and 

 the curious carnivorous plants ( 20). 



198. Swamp forests. Often trees encroach upon peat- 

 bogs, and a swamp forest is the result. The chief types in 

 this case are the conifers, and on this bog-moss foundation 

 there occur larches, certain hemlocks and pines, junipers, 

 etc. The larch or tamarack is a very common swamp 

 tree of the northern regions, usually occurring in small 

 patches; while the larger swamp forests are composed of 

 dense growths of hemlocks, pines, etc. (Fig. 306). 



199. Salt marshes and meadows. The salt marshes and 

 meadows near the seacoast are well known. They lie 

 beyond the reach of ordinary flood-tide, but the waters are 

 brackish. In these marshes occur certain characteristic 

 salt-water grasses and sedges, giving the meadow-like ap- 

 pearance; while associated with them there are numerous 

 succulents, that is, fleshy plants, characteristic of brackish 

 water. 



200. Mangrove swamps. This is the most vigorous salt- 

 water association. Mangrove swamps occur along flat 

 tropical seacoasts where the waters are quiet (Fig. 307). 

 The mangrove is a tree of curious habit, advancing slowly 

 out into the water by means of its prop-roots and peculiar 

 seeds. The seeds germinate while still upon the tree, so 

 that the embryos hang from the trees and then drop like 

 plumb-bobs into the muck beneath, where they stick fast 

 and establish themselves. 



