VEGETATION OF ROCKY PLACES. 607 



ground is built up to water-level, when it passes into the type of 

 the meadow swamp. 



1099. Meadow-swamp societies, or meadows. These repre- 

 sent a progressed stage of the mud or reed swamp. Grasses and 

 sedges suited to growing in wet soil or in swales follow the reed- 

 grass and scirpus, forming meadow-like expanses. Here and 

 there one or more species of grass or other herb would dominate 

 and make the formation, as Cyperus formation, Carex formation, 

 or the true grasses, according to the dominant species. A lux- 

 uriant vegetation is usually formed because the soil is black and 

 rich with nitrogenous plant-food, and the low situation of the 

 ground assures an abundance of ground-water. These are the 

 true meadows, though the name is given popularly to any meadow- 

 like expanse on higher ground where grasses are the dominant 

 vegetation forms, whether in waste places or cultivated areas. 

 See also meadow-moors in the following paragraph. 



1100. Peat-moor societies, or bogs (also called muskeag). The 

 ground of the peat-moor or peat-bog is largely composed of peat 

 characterized by an abundance of vegetable matter. In the 

 moor only partial decay of vegetation takes place. This is due 

 to an abundance of water, which accounts for the small amount of 

 oxygen, the absence of the kinds of bacteria and fungi which 

 reduce vegetation to humus and finally to plant-food. There 

 is produced then an abundance of humus acid in the form of 

 humates. Two kinds of peat-moors are recognized by some, 

 characterized by the presence or absence of lime. The "high" 

 moors have an abundance of free humus, but lime is lacking, 

 while in the so-called meadow-moors, which do not have such a 

 thick ground formation, the humus acid is combined with lime. 

 Both of these kinds of moors are poor in mineral substances 

 because, being built up of decaying vegetation in the water, 

 the decay is only partial, "ground" is built up rapidly upon the 

 bottom of the pond, and rock-soil constituents are largely ex- 

 cluded. They are rich in nitrogenous matter, but this is com- 

 bined with humus in the form of humified albuminous bodies. 

 It is thus not readily available for plant-food. This, together 



