ROCK PLANTS 



from the sunny shores of the Mediterranean. They are 

 mostly annuals, such as the little Toadflax {Linaria minor), 

 which can just manage to exist under those conditions. 



Of course, the sides of the banks and of cuttings on rail- 

 ways are generally formed of good earth or soil, and support 

 a rich and flourishing flora of true Britons. 



Besides these slow, laborious lichens, mosses, and others 

 which attack rock, there are other plants which are generally 

 called rock plants, though they behave quite differently. 



These are those fine hardy Hawkweeds, Roseroots, Semper- 

 vivums, Mew, and others which establish their roots in cracks 

 or crevices of the rocks. 



Such cracks are soon full of good soil, for the wind blows 

 decayed leaves and dust into them, and the roots are always 

 burrowing into, eating into, and shattering the rocks. 

 Most of them have a circle of leaves which are pressed flat 

 to the ground. Thus they escape the violent winds and 

 storms always common on such crags and precipices. The 

 flowers, however, supported on tough, strong, and flexible 

 stalks, sway freely to and fro in the wind, and can be seen by 

 insects a long way off*. 



These rock plants are of some importance as stonebreakers 

 and pioneers in a very interesting process. 



Wherever a cliff" or precipice of stone is exposed, it is 

 "weathered." Water gets into the cracks and freezes in 

 winter. But when water is frozen it expands or widens, and 

 as this happens to the water in the crevices and cracks of 

 rocks, pieces of rock are shivered and broken off. Besides 

 frost and wind and rain, these rock plants help to attack 

 the cliff". Their roots get into the crevices, and there 

 widen and expand, tearing off* great slabs and splinters of 

 rock which fall down to the foot of the cliff. 



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