266 PLANT LIFE. 



off at every fourth leaf, and the stems die off at the 

 base. If there is sufficient moisture they are always 

 growing upwards. Thus, if one remembers that these 

 stems are placed closely side by side in a sort of 

 cushion, and that this cushion is able either to float in 

 water or to grow on saturated mud, it is clear that there 

 is no limit to the peat moss formed by the Sphagnum, 

 provided always that there is no lack of water. 



Peat mosses of extraordinary depth are known. 

 Some of those in East Prussia are from 18-30 feet 

 deep ; and even our own Scotch mosses may be 

 20 feet deep or more. The growing Sphagnum cushion 

 very often floats on the water or on the liquid mud. 

 When heavy rain has been falling for a long time, water 

 may accumulate in great quantities over the dead peat, 

 and under this cushion of growing Sphagnum and other 

 plants. It sometimes happens in these circumstances 

 that this living crust bursts, and a deluge of peaty 

 water or mud overflows the surrounding country. This 

 took place not very long ago at Killarney ; and similar 

 peat floods have been recorded elsewhere.^ 



Generally speaking, the Sphagnum moss is not con- 

 tinuous. There are firmer places where the neighbour- 

 ing vegetation obtains a footing. Such plants as Sweet 

 gale {Myrica), Birch, and Heather, are to be found in 

 most peat bogs, as well as a sort of superficial flora, 

 which extends over the drier parts, but whose roots do 

 not penetrate deeply into the peat. This flora includes 

 Sundews {Drose^^a) and Cranberries ( Vaccinium oxycoccos). 

 As the supposed Sphagnum moss developed continuously 

 in the same place since the glacial period, it has been 



^ Rathmore moss, where 200 acres overflowed and nine persons were 

 killed in 1896, Crowbill bog at Keigbley in 1824, a Lancashire moss in 

 1745, an I a bog of 40 acres at Charleville in 1697, are the best known 

 examples. 



