Mans Work on the Farin 339 



ground has been cleared of wood and then left to itself, 

 it is covered in a few j^ears, first with shrubs, then 

 with trees, chiefly of the pine tribe. In eight years, it 

 will become a coppice with saplings five or six feet 

 high ; and all this without any further interference on 

 the part of man. 



Man makes the vacancy, and nature, if only let 

 alone, fills it again. There are parts of the United 

 States where pine-woods have been cut down for 

 railway purposes, and have been at once followed by 

 oaks, planted by some or other of nature's many 

 labourers. Why pines should not have sprung up 

 again, when their seeds must, one would imagine, 

 have been present in the soil, seems to be one of 

 the many questions still waiting to be answered ; 

 but it is a well-known fact that in many places 

 where forests are cut down, trees of an entirely 

 different kind do spring up in their place. And of 

 course different trees mean different insects, and 

 different birds. 



Mr. Darwin mentions some remarkable changes of 

 this sort brought about simply by the enclosure and 

 planting with Scotch fir of a very barren heath in 

 Staffordshire never before touched by man. In five- 

 and-twenty years, the vegetation of the planted and 

 unplanted portions had become so different that the 

 soil might have been supposed to be of quite distinct 

 kinds. Within the plantation there were fewer heath- 

 plants, but there were also twelve species of other 

 plants, not counting grasses and sedges, which were 

 not to be found on the heath at all. Six species of 

 insect-eating birds, too, were common in the planta- 

 tion, but did not stray outside it ; while two or three 



