490 BOTANICAL GAZETTE [june 



a continuous decline in the moss flora until the climax beech-maple 

 forest is reached. Competition with other plants seems to be the 

 determining factor as the successions advance beyond the semi- 

 hydrophytic. 



Conclusions 



i. In the successions on sand, mosses are most abundant, both 

 in number of species and in total quantity in the stage; in which 

 they first become very noticeable, the pine stage; and they decrease 

 through the early oak stages to either the oak or the beech-maple 

 climax. 



2. In the swamp and bog successions the greatest dominance 

 of mosses is found usually in the swamp or bog forest association, 

 which may or may not directly precede the climax. 



3. The mosses found in running spring water and in stagnant 

 water are of different species, but nearly all belong to the same 

 family, the Hypnaceae. 



4. The succession on floodplains is unimportant because of 

 constant deposit of sediment over the germinating mosses. 



5. Mosses are among the highly important pioneer plants on 

 bare rock surfaces, and continue abundant far into the forest 

 association. 



6. From an economic standpoint mosses are of the greatest 

 value in several respects. They are soil formers and provide 

 favorable habitats for germination of higher plants. They assist 

 largely in forming the surface mat over deep lakes and in filling 

 up shallow bodies of water. They may take part in building 

 up rocklike substances, as tufa. They help to make up floating 

 islands on which higher plants may grow. They conserve moisture, 

 and give it up slowly, thus aiding in the prevention of disastrous 

 floods in the surrounding regions. They prevent erosion of clay 

 or sand surfaces. 



