412 



BROOKLYN BOTANIC GARDEN MEMOIRS 



factors. In various places the decomposed remains of an earlier 

 vegetation led to mechanical and chemical changes in the soil, the 

 extent of which was more effective toward breaking up the flora into a 

 heterogeneous formation, accompanied by a frequent replacement of 

 one dominating group by another." 



There are some bogs without evidence of marl at the bottom. 

 Davis reports all the many peat bogs examined by him in Maine as 

 resting on sand, clay or rock bottom, none on marl. Most of the 

 peat bogs in the Adirondack region of New York have no marl at the 

 bottom. These presumably were from the first supplied by springs 

 of non-alkaline water. Some of the peat bogs of central and western 



Fig. 2. Peat bog near McLean, Tompkins Co., N. Y. Chamaedaphne, Andro- 

 meda, Ledum and other heaths together with Sphagnum form the dominant vegeta- 

 tion. 



New York have great masses of marl under them. Such a one is near 

 Peterboro in Madison County and another on Gorham Creek in On- 

 tario County. Here it is apparent that some agency changed the 

 composition of the water to such an extent that oxylophytes found 

 conditions congenial. 



The most extensive marl ponds in the region are in the vicinity 

 of the limestone belt of central New York. They occur at West 

 Junius in Seneca County and southwest of Rochester, especially at 

 Bergen in Genessee County. Isolated and much smaller marl ponds 



