

HYDKOPHYTE ASSOCIATIONS. IS"! 



of nearly reclaimed ponds may be noticed, where bul- 

 rushes, cat-tail flags, and reed grasses still occupy certain 

 wet spots, but are shut off from further migration. The 

 social growth of these plants, brought about by extensive 

 root stock development, is especially favorable for detain- 

 ing detritus and building a land surface. 



Reed-swamp plants also have in general a tall and nn- 

 branched habit of body. They may be bare and leafless, 

 with a terminal cluster of flowers, as in the bulrushes ; or 

 the wand-like stems may bear long, linear leaves, as in the 

 cat-tails ; or the stem may be a tall stalk with two rows of 

 narrow leaves, as in the reed grasses. Xo more character- 

 istic group of forms is found in any association. Of course, 

 associated with these forms are also free and fixed hydro- 

 phytes, that characterize the other associations. 



138. Swamps. — The word is used to include the ordinary 

 meadow-like expanses of swampy ground, but does not in- 

 clude such associations as peat bogs. There is less water 

 than in the case of the reed swamps, and often very little 

 standing water. One of the peculiarities of the swamp 

 is that the water is rich in available soil materials used 

 in food manufacture, notably the nitrates from which 

 nitrogen is obtained for proteid manufacture. In such 

 conditions, therefore, the vegetation is dense, and the soil 

 is black with the humus derived from the decaying plant 

 bodies. 



Typical swamps border the reed swamps on the land 

 side, and slowly encroach upon them as the reed plants 

 build up land. Probably the most characteristic plait 

 forms of the swamp association are the sedges, and asso- 

 ciated with them are certain coarse grasses. These give 

 the meadow-like aspect to the swamp, although these 

 grass-like forms are very coarse. Along with the domi- 

 nant sedges and grasses are numerous other plants adapted 

 to such conditions, such as some of the buttercups. It 

 would be impracticable to give a list of swamp plants, as 



