488 BOTANICAL GAZETTE [june 



onal dry seasons and frequent deposit 

 mosses soon leads to accumulation o 



sem 



goon region is a tar more 



as to actual number of ponds and variation in ecological develop- 



ment, a 

 lagoons. 



mosses from one pond to 



much better; the variation in depth permits 



both of floating and fixed species, while the greater age has allowed 



time for accumulation of more 



more 



growth of all. With these conditions comes the rapid advance of 

 the shrub and forest or prairie successions. In the swamp forest 

 the moss flora becomes increasingly a dominant factor in humus 

 accumulation as the ecological succession advances toward the 

 climax, but berins to decline with the close anoroach of the beech- 



m 



com 



tion with other ground flora and of the smaller supply of available 

 water near the surface. 



Very little work has been done in determining conditions for 

 plant life in the bogs, but from the xerophytic structures of many 

 bog plants, and the shallow root systems of the trees, Cowles 

 concludes that, while moisture is plentiful, the chemical content 

 of the water is such as to have a toxic effect upon the root develop- 

 ment of plants, and to prevent absorption of water to a great 

 extent. In other words, this is a physiologically xerophytic habitat 



for seed plants. 



may influence 



mosses; that it is not very injurious 



the great abundance of some species, such as Sphagnum. On the 

 sedge mat the shade may be considerable when cat-tails are 

 abundant, but the sun's rays reach the ground more directly than 

 in the forest. The humidity near the ground is probably greater 



times is also much 



small 



them, forming 



stems, but there are no large masses. In some places there is 



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