334 PLANT LIFE. 



like the Poppy and Cudweeds, are adapted to drier 

 conditions than those prevailing in an ordinary meadow. 

 But the raihvay-track, and shale-heap flora is of 

 decidedly Southern affinity. Many Mediterranean 

 species are able to live perfectly well upon the cinders 

 and shale of Scotch railway lines, though they never 

 spread into the surrounding country. This artificial 

 ground flora varies greatly in different places. Each 

 shale heap seems to have an individuality of its own, 

 although a gradual occupation by one species after 

 another, is usually quite clearly marked in any one 

 district. 



Near Glasgow, the usual succession on the flat top 

 of such a shale heap and on its sides, is often quite 

 different. On the sides scattered specimens of Senecio 

 viscosus appear able to develop almost anywhere, even 

 on the steepest and most weathered slopes. From the 

 base of such a heap masses of Equisetuni arvense and 

 the skirmishing runners of the Colt's Foot extend some 

 distance upwards. If they are at all favoured by a 

 depression or miniature ravine, the Colt's Foot may 

 even reach the summit. After these Equisetums and 

 Colt's Foots have affected the shale for some little 

 time, He7'aclemn spondylium^ and a few other coarse- 

 growing plants make their appearance. Occasionally, 

 but not often, masses of Grasses or of Hieracia may be 

 found on old slopes. Both Hawthorn and Roses are 

 also able to root on the sides of these heaps. On the 

 summit a much more varied flora is able to exist. 

 One of the most characteristic types is a Hieracium, 

 found in extraordinary quantities, and often almost by 

 itself Between the leaves of this plant the ground is 

 thickly covered by low tufted mosses. 



The most remarkable point is the absence of many 



