CH. XIX THE PHYSICAL CONDITIONS ' 205 



cut them up and carefully examined them, and under their 

 guidance we have explored the mangrove-swamps both of Polynesia 

 and of Ecuador, and have penetrated the mysterious cul de sac of 

 vivipary. Having formed our opinion of them, we now bid the 

 subject farewell, and stand once more on the same Pacific beach 

 where, it seems so long ago, our investigations began. 



For the seed and fruits lying at the bottom of the sea-water we 

 have to appeal to other agencies than to that of the currents if we 

 wish to inquire into their means of arriving at this island. In 

 imagination we leave the reef-lined shores for the interior, and 

 exchange the exhilarating surroundings of a coral beach, where 

 " the sky is always blue and the wind is always true," for the arid 

 conditions of an inland plain, or for the humid conditions of the 

 forest, where the rain is incessant and the cloud-cap and mist 

 seemingly eternal. When we look at the motley collection of fruits 

 and seeds obtained in such localities, we are at a loss to know 

 where to take up the clue. After vainly endeavouring to obtain 

 some inspiration as to the manner of commencing the inquiry, we 

 do what all good naturalists in the Pacific islands do from force of 

 habit when they meet with difficulties of any kind — we sit down and 

 light our pipes. Then come a flood of old memories and old trains 

 of thought that came to us years before on some mountain-top or 

 in a shady gorge or on some river-bank, in regions Pacific and non- 

 Pacific, and by degrees our ideas shape themselves and we begin to 

 think the matter over in an orderly fashion. 



When the winds first brought the spores of ferns to this Pacific 

 island, the ocean currents brought the seeds and fruits of littoral 

 plants, and the birds transported the seeds and " stones " of various 

 inland species. All three agencies have been working side by side 

 since the earliest stage in its history. Yet it is only in the work of 

 the wind and the current that we find any indication of stability in 

 the floral history of the island. With the work of the bird it has 

 been very different. Since the first bird carried seeds to this 

 locality all else has been turmoil and change. Wave after wave of 

 migrant plants has overrun the interior of the island, and all have 

 left their mark ; but the great distributing factor and disturbing 

 agent has always been the bird. Genera have been born and have 

 disappeared, and in their place new genera have arisen. Whole 

 families even have participated in the revolutions of the plant-world, 

 and species have grown rankly in the great confusion. Last of all 

 came man with his cultivated plants and his weeds, introducing 

 new elements of change and discord into the island, and often up- 



