312 THE VOYAGE OF H.M.S. CHALLENGER. 



they will doubtless be recognised when Dr Guppy's dried plants from the same islands are 

 compared. There are two species of Ficus, a Psychotria ? a Eugenia, a Premna ? and 

 an Areca. 



CONCLUDING REMARKS ON THE DISPERSAL OF PLANTS BY OCEANIC 



CURRENTS AND BIRDS. 



It is hoped that the foregoing collection of facts bearing upon the dissemination of 

 plants by oceanic currents and birds will sufficiently interest and stimulate those persons 

 who have opportunities for observing the effects of these agencies in various parts of the 

 world to observe and record the results of their observations. There can be no question 

 that a large number of trees, shrubs, and herbs, many of them not essentially littoral, 

 have been transported to distant countries by the agency of the sea, and that the area of 

 many plants thus conveyed from place to place is only limited by climate and the nature 

 of the shore upon which their seeds may be cast. That birds are also great seed-carriers, 

 and assist largely in local diffusion, is equally certain, but facts are wanting to establish 

 their reputed influence in materially widening the areas of species. Darwin fully discusses 1 

 the probabilities and possibilities of the occasional transport of seeds long distances by 

 birds in various ways. " Almost every year," he states, " one or two land-birds are blown 

 across the whole Atlantic Ocean, from North America to the western shores of Ireland and 

 England," and he points out the possibility of small seeds being by this means conveyed 

 long distances in mud sticking to the claws or other parts of the bird. He expresses the 

 opinion that even if the occurrence be very rare, birds do convey seeds to vast distances, 

 especially those of water and marsh plants. In nine grains of earth taken from the leg of 

 a woodcock was a seed of a common rush (Juncus bufonius), which on trial germinated ; 

 while from the seeds contained in a ball of earth taken from the leg- of a wounded 

 partridge, no fewer than eighty-two plants, belonging to five species, were raised. In 

 order to ascertain the probabilities of seeds being contained in the mud on the edge of a 

 pond, three table-spoonfuls were taken from different points. "This mud weighed when 

 dry only 6§ ounces; I kept it covered up in my study for six months, pulling up and 

 counting each plant as it grew. The plants were of many kinds, and were altogether 537 

 in number ; and yet the viscid mud was all contained in a breakfast cup ! " 



In relation to the dispersion of plants by birds and oceanic currents Dr Beccari's 2 

 observations on the flora of the Arrou Islands have a special interest. He says he had 

 no great hopes of discovering zoological novelties, but he was not prepared for the meagre 

 flora that he found. Four months' continuous exploration yielded only between three and 

 four hundred species of plants. Such poverty, he adds, I could not have imagined. 



1 Origin of Species, ed. i., pp. 3G3 and 38G. 



2 Nuovo Giornale Botanico Italiano, v., 1873, p. 330. 



