SOIL FORMATION: MOORS. 389 



the surface, and then certain aquatic plants like bidens, and 

 others, find a footing. Upon this black ooze the formation can 

 continue to encroach upon the central pond. Agitated by the 

 wind, more and more of the ooze passes outward, so that in time 

 there is a likelihood that the pond will cease to exist, yielding, 

 as it has in other places, the right of possession to the conten- 

 tious vegetation. 



700. How was the atoll formed? — In the early formation of 

 the atoll, it is possible that certain of the water-loving carices and 

 grasses began to grow some distance (three to four meters)- from 

 the shore, where the water was of a depth suited to their habit. 

 The stools of these plants gradually came nearer the surface of 

 the water. As they approach the surface, other plants, not so 

 strong-rooted, like mosses, sphagnum, etc., find anchorage, and 

 are also protected to some extent from the direct rays of sunlight. 

 Partial disintegration of the dead plant parts and mingling with 

 the soil gradually fills on the inside of the zone, so that the depth 

 of the water there becomes less. Now the zone of the carices 

 can be extended inward. 



701. The continued growth of the sphagnum and the dying 

 away of the lower part of the plant add to the bulk of the plant 

 remains in the zone, and finally quite a firm ground is formed, 

 shutting off the shallow water near the shore from the deeper 

 water of the pond. As time goes on other plants enter and 

 complicate the formation, and even make new ones, as when the 

 cassandra takes possession. 



702. The original pond here was rather oblong, and one end 

 possibly much shallower than the other, so that it filled in much 

 more rapidly, leaving the central pond at the east end. Over 

 a portion of the west end there is an extensive cassandra forma- 

 tion, with some ledum (lab rador tea), but separated from the 

 circular cassandra zone by an intermediate zone. In this end- 

 cassandra formation other shrubs, and white pines five to fifteen 

 years old, are gaining a foothold, and in a quarter of a century 

 or more, if left undisturbed, one may expect considerable changes 

 in the flora of this atoll, It is possible that a rise of the water 



