How to Know the Lichens and Mosses 



oxygen gas (O) is set free to return to the atmosphere, and the 

 solid carbon (C) is worked up with water into plant foods called 

 carbohydrates, compounds of carbon and water, of which starch, 

 sugar, and plant tissues are examples. 



" A small sisterhood of plodding lichens 

 Wrought on the rock ; the sun, the wind and rain, 

 Helping then gladly, till each fissure filled 

 And fit for planting, mosses came in haste 

 And strewed small seeds (spores) among them, destined they 

 To clothe the stern old rock with softest verdure 

 With ferns and flowers, where yet the labouring bee 

 May find pasture." 



Certain lichens carried by the winds to places unsuitable for 

 other plants, begin their work of dissolving the inhospitable rock 

 to obtain mineral salts which the leaf-green may, together with 

 water, manufacture into plant food; the delicate threads of the 

 lichen work their way in and out among the particles of rock too 

 small to be visible to the naked eye, and as they swell with 

 water absorbed from the atmosphere, they pry off tiny particles 

 of rock, thus slowly but surely preparing soil for higher forms. 



The mosses also can take their start in life on bare and rugged 

 rock, although not so generally as the lichens. 



If a tuft of Grimmia apocarpa is lifted away from the lime- 

 stone upon which it is growing, one may see corroded depressions 

 in the neighbourhood of the place where the stemlets of the moss 

 colony meet, and one may see the rhizoids of the moss imbedded 

 in loose particles of limestone which have been separated from 

 the main rock by a dissolving fluid which the rhizoids secreted 

 upon the rock. In this way the moss obtains mineral salts which 

 are necessary for its growth. The solid rock is crumbled to a 

 dust which may be blown by the wind to other localities, or 

 which may remain on the spot and furnish soil for higher plants. 

 In addition to the chemical action which the moss exerts in 

 dissolving the rock, it, as well as the lichen, exerts a purely 

 mechanical influence, for a growing rhizoid penetrates wherever 

 the merest particle of limestone has been dissolved and by 

 mechanical pressure separates the particles of limestone which 

 remain. 



The mosses and lichens are truly efficient agents in rendering 

 rocks available for plant life by retaining minute particles of soil 



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