MOSSES 



At any rate, one of thes?e little crust-lichens called Vario- 

 laria has been known to increase half a millimetre in size 

 (about a sixtieth part of an inch) between the end of 

 February and that of September. 



Now if one tries to realize what the life of such a lichen 

 crust or crottle must be, it is obvious that the stone below 

 it must be a little corroded or weathered, and remains of the 

 first choked pioneers, bacteria, and possibly tiny insects or 

 animalcula will be under the crust, which may now be one- 

 sixteenth of an inch thick. 



It is the turn now of other lichens to colonize it. These 

 may be the little trumpet or horn and cup lichens, Cladonias, 

 or perhaps the larger grey kinds, Parmelias and Physcias^ 

 which have leaf-like fronds and form circles of perhaps 

 eight to ten inches in diameter. The crust-lichen is over- 

 grown, broken up, disorganized, and devoured by the Par- 

 melias and Cladonias, who are helped by bacteria, insects, and 

 animalcula which shelter below them. These leafy lichens 

 grow much more rapidly. 



They may increase two-thirds of an inch in one year. 



But very soon after this, one notices a few inconspicuous 

 green mosses; at first in crevices between the stones or in 

 hollows, and not remarkable, they soon increase and form trail- 

 ing sprays or branches which grow very quickly. Branches 

 of moss four or five inches long extend over the leafy 

 lichens in a season. The Parmelias and Cladonias struggle 

 on, but they cannot keep pace with the rapid life of the 

 moss, and soon our wall is covered by beautiful moss turfs. 



Underneath such a turf there may be an inch or so of 

 good soil (dead moss and dust with lichen and insect bodies). 

 Worms, insects, etc., shelter and flourish and multiply in this 

 soil. 



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