FOREIGNERS ON RAILWAYS 



mosses, to hawkweeds, and other rock plants. These in time 

 cover the top, and soon hardy grasses and weeds form a 

 regular turf on the top of the shale. 



It is interesting to scramble to the top of one of these 

 heaps, especially in summer. One then begins to realize how 

 every plant attends strictly to its own business. 



All over the sides of the heap there will be hundreds of 

 a rare groundsel {Senecio viscos%is\ which is not really a 

 native, and never occurs except on such places. In a grass 

 field close by hundreds of thousands of Ragwort {Senecio 

 jacohoed) make a glorious golden carpet ; in the marshy part 

 of the meadow the Water Ragwort {Senecio aquaticus) may 

 be found. In the cottage gardens and here and there 

 along the roadside the groundsel {Senecio vulgaris) is 

 flourishing abundantly. 



These plants never interfere with or encroach upon one 

 another's grounds. Every year thousands of ragweed and 

 groundsel seeds must be blown on to the shale-heap, but 

 they never manage to grow there. 



It is only the foreigner {S. viscosus), accustomed to a very 

 hot and dry climate, and with sticky leaves which catch atmo- 

 spheric dust and probably insects, that can exist on the bare 

 shaly sides. These slopes of shale are easily heated by the 

 sun, and at the same time radiate the heat rapidly away, so 

 that the Viscid Groundsel must have a very hard time of it. 

 When its roots have worked up the shale a little, and its 

 dead leaves have covered the surface with mould and organic 

 matter, then possibly others (true British plants) can get 

 a footing and suppress it. 



Along railway tracks, also, the ballast forms a very hot, 

 a very dry, and a very barren soil. Many of the regular 

 railway-track plants are foreigners from the far south, even 



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