SOIL FORMATION: ROCK DISINTEGRATION. 319 



to a pole two or three meters long in thrusting it down these 

 holes. Grasses, carices, mosses, sphagnum, and occasionally 

 moor-loving dicotyledons occur, anchored for the most part 

 about the roots of the cassandra. Standing at the inner margin 

 of the cassandra zone, one can see the mud, resembling a black 

 ooze, formed of the titrated plant remains, which have floated 

 out from the bottom of the older formations. In some places 

 this lies very near 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 out- 

 ward, 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 contentious vegetation. 



484. 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 fill 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. 



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. 



The original pond here was rather oblong, and one end possi- 

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



