THE ALGJZ IN LICHENS 



position, rich in nitrogen, furnishes by endosmose 

 that element essential to plasmodic structure ; whilst 

 it in return receives from the chlorophyll cellules 

 of the algae the carbo-hydrides that they have 

 formed from the atmosphere, and by which the tissues 

 and the starch-like or gelatinoid elements of the lichen 

 can alone come into being. 



Lichens, beside the important part they play in the 

 general economy of nature in promoting, as already 

 described, the formation of soil for the growth of the 

 higher order of plants, contain many valuable plants. 

 Cetraria, or Iceland Moss, furnishes a valuable food 

 in regions where other food is scarce. The Reindeer 

 depend for their existence on another variety, and 

 many valuable dye-stuffs are prepared from other 

 species. 



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