THE INFLUENCE OF MAN. 335 



plants very characteristic of waste ground, such as 

 Polygonum Persicaria, Chickweed, Spurrey, and the Nettle. 

 Standing on one of these heaps, one may see on the 

 one side a grass field, in which there are hundreds and 

 thousands of Senecio Jacobaea, Ranunculus acris^ Docks, 

 and other weeds ; on the other, a field of turnips, in 

 which Polygonum, Spurrey, and Chickweed exist by the 

 hundred thousand ; but a close search on the summit 

 will only reveal perhaps three plants of Ragwort, half a 

 dozen Docks, and not one single example from the 

 turnip field. 



Yet the explanation is simple. The shale heap is 

 unprepared soil similar to the barren rocks on which 

 the Highland Hieracia develop. The grass and turnip 

 fields are richly prepared by manure, and by the work of 

 generations of crops carried on during many years. On 

 older heaps plants of Heracleum, sometimes with roots 

 five feet deep, and a great variety of other plants are 

 found. Ranunculus repens also often covers the ground 

 with a network of prostrate stems. Grasses after this 

 begin to form a sort of sward, and odd plants of Senecio 

 Jacobaea, Dock, Thistle, Plant ago Lanceolata, Mouse-ear 

 Chickweed may eventually develop. Hawthorn and Roses 

 are quite common, though Brambles are decidedly 

 unusual. For some reason the stolons of the Bramble, 

 even when the plant is grown outside, but close to the 

 base of the shale heap, seem unable to send their 

 roots into the shale, and they lie flat on its surface 

 in a limp and unhealthy-looking manner. The com- 

 parative poverty of the sides is probably due to the 

 steep angle, which involves the washing away of the 

 organic matters, as soon as they are formed. It might, 

 however, be quite possible to cover both the top and 

 sides of such a heap with a thicket of Roses. 



