Chances of Life 295 



sure multitudes of seedling trees were to be seen ; 

 outside, none. Yet they were there, plenty of them, 

 striving, but failing, to get their heads above the 

 heather, because perpetually browsed down by the 

 cattle. One aged seedling, three inches high, had been 

 making persevering but fruitless efforts for six-and- 

 twenty years, so it seemed, from the number of its 

 annual rings ; and, but for the cattle, the heath would 

 quickly have become a wood. 



Space, as we have said, is a matter of prime import- 

 ance, and the reason why tropical ferns and orchids 

 have been so successful in establishing themselves in 

 the islands of the Southern Ocean is not only because 

 their seeds are plentiful and easily carried, but because, 

 as they can grow upon other plants, they are never at a 

 loss for vacant spots. 



Bare spaces are otherwise not of frequent occurrence 

 in nature, except on mountains, where landslips on a 

 large or small scale are often taking place and exposing 

 fresh surfaces. These are quickly sown with seeds 

 either by the winds or by the birds, and hence moun- 

 tain chains are very common routes by which plants 

 travel, gradually making their way along them by easy 

 stages. Railway embankments, too, are turned to 

 similar account ; and people are sometimes surprised 

 to see these occupied for a time by plants which are 

 quite strangers to the neighbourhood, the fact being 

 that the seeds, though scattered, have never before had 

 the luck to fall on a free space. Plants which thus 

 gain a footing may or may not be able to keep it ; they 

 may be overpowered by the natives of the locahty, but 

 even so, if they blossom and bear fruit but once, they 

 have gained an onward step, a fresh centre from which 



