DISTRIBUTION OP THE RAINFALL. 291 



I do not like the expression " struggle for possession " being applied 

 to vegetation ; I prefer making use of the corresponding expression, 

 " survival of the fittest ;" bnt the expression " struggle for possession " 

 has come into more general use. 



In illustration of what has been likened to a struggle for possession 

 between immigrants and earlier settlers, let me refer to what may 

 sometimes be seen, in our own day, on a flowery bank of one of our 

 hedge-rows, or by the side of a country walk. Let it be supposed 

 that the case is one in which the flowers consist mainly of dog violets 

 and of pausies in equal proportion. Any other plants would equally 

 serve for illustration ; these are selected of design. If such a bank 

 were revisited, after some years of absence, it might be found as 

 flowery as ever ; but the flowers would not be all of the same kinds, 

 in the same proportion, as bsfore. Amongst other changes, it may be 

 that either the pansies or dog-violets would have disappeared, and 

 the species remaining would be more numerous than either were. 

 By transmutation or development 1 Oh, no ! not at all ; but thus : 

 the soil exposure, heat, and moisture could scarcely fail to be more 

 adapted to the requirements of the one than to those of the other : 

 in an infinitely minute degree it might be, but still the difference 

 was there ; and even if the quantity of seed cast by each plant 

 should have been precisely equal, this infinitely minute diS'erence of 

 adaptation would sufl&ce to bring about the change. 



I shall magnify the effect to make it more apparent. If there 

 were a hundred plants of each when first observed, in the year 

 following there might be 105 of the one and only 95 of the other; 

 in the year after there would be the progeny of 105 plants of the one 

 and the progeny of 95 of the other less favourably situated species, 

 and this might present us, not with 110 of the one and 90 of the 

 other, but perhaps 112 of the one and 88 of the other; and the dis- 

 proportion in years following would go on increasing in a corre- 

 sponding accelerating ratio. And indications of something like this 

 having occurred in forests have been observed : a forest of mixed 

 trees giving place to one of uniform production. And thus may the 

 successions have occurred, while the seeds of trees which had not 

 germinated lay dormant, awaiting their time to germinate whenever, 

 in the changes accompanying progressive desiccation, the dominating 

 trees should succumb, and they be able with greater success to take 

 their place. 



From a work by Vaupell we learn that the earlier forests of Den- 

 mark were composed of birches, oaks, firs, aspens, willows, hazel and 



