326 



ECOLOGY. 



individual plants, while the older portions below die off, partly 

 disintegrate, and pass over into the increasing solidity and bulk 

 of the peat. It thus happens sometimes that the centres of 



Fig. 269. 

 Cypress knees, Mississippi. (Photograph by H. von Schrenk.) 



such basins or moors are more elevated than the margins, 

 because here a greater amount of water exists in the depths 

 which is pumped up for use by the plants themselves. Such a 

 formation is sometimes called a " high moor." 



492. Change in form. Because of the peculiar topographic 

 features of these basins, together with the conditions of mois- 

 ture, etc., changes in their form are quite readily observed. 



