382 A NATURALIST IN THE PACIFIC CH. xxvn 



others ; and here also the migrant bird, having from some cause 

 changed its ways, has given rise to new varieties and to new 

 species. It is with this loss of the migratory powers of the birds 

 of the forest-zone that I connect many of the important differences 

 between the forest-floras of the different groups of the Pacific. 

 At one time, it would seem, birds were far more active agents in 

 dispersing seeds and fruits over these archipelagoes than they are 

 at present ; but it is not held that this is concerned with the 

 extermination and extinction of the birds of these islands in the 

 present day. The change dates far back and is far-reaching in its 

 effects. It is assumed in this argument that the alpine plant and 

 the plant of the pond and of the sea-shore preserve their characters 

 by reason of the means of free dispersal that they still enjoy ; and 

 it is inferred that the plant of the forest-zone has varied more 

 because opportunities of transportal of its kind no longer are 

 afforded. Many a line of ancient migration is now broken. 



It is suggested that in the past when birds were more gene- 

 ralised in type they were much more migratory in habits and that 

 limitation of range has been associated with specialisation. The 

 plants dispersed by the birds have undergone *a parallel series of 

 changes. At first widely distributed, as in the more generalised 

 types of birds, they became localised in proportion as the birds to 

 which they owed their means of dispersal lost their migratory 

 ways ; and both plant and bird began to vary. There is, I am 

 convinced, a profound connection between birds and plants, of 

 which we now perceive only the last of a long series of changes. 

 This subject will be dealt with at length in the volume on plant- 

 dispersal ; and it is only referred to here to illustrate my contention 

 that we have yet much to learn before it would be safe to look to 

 hypothetical changes of sea and land to explain difficulties in 

 distribution. 



