808 MEANS OF DISPEESAL. [CHAP. XII 



might readily be the means of introducing several kinds of plants 

 into an island lying far from the mainland. 



Although the beaks and feet of birds are generally clean, earth 

 sometimes adheres to them : in one case I removed sixty-one 

 grains, and in another case twenty -two grains of dry argillaceous 

 earth from the foot of a partridge, and in the earth there was a 

 pebble as large as the seed of a vetch. Here is a better case : the 

 leg of a woodcock was sent to me by a friend, with a little cake 

 of dry earth attached to the shank, weighing only nine grains ; 

 and this contained a seed of the toad-rush (Juncus bufonius) 

 which germinated and flowered. Mr. Swayslaiid, of Brighton, 

 who during the last forty years has paid close attention to our 

 migratory birds, informs me that he has often shot wagtails 

 (Motacillae), wheatears, and whinchats (Saxicolse), on their first 

 arrival on our shores, before they had alighted ; and he has 

 several times noticed little cakes of earth attached to their feet. 

 Many facts could be given showing how generally soil is charged 

 with seeds. For instance, Prof. Newton sent me the leg of a red- 

 legged partridge (Caccabis rafa) which had been wounded and 

 could not fly, with a ball of hard earth adhering to it, and Aveigh- 

 ing six and a half ounces. The earth had been kept for three 

 years, but when broken, watered and placed under a bell-glass, no 

 less than 82 plants sprung from it : these consisted of 12 mono- 

 cotyledons, including the common oat, and at least one kind of 

 grass, and of 70 dicotyledons, which consisted, judgirg from the 

 young leaves, of at least three distinct species. With such facts 

 before us, can we doubt that the many birds which are annually 

 blown by gales across great spaces of ocean, and which annually 

 migrate for instance, the millions of quails across the Mediter- 

 ranean must occasionally transport a few seeds embedded in dirt 

 adhering to their feet or beaks ? But I shall have to recur to this 

 subject. 



As icebergs are known to be sometimes loaded with earth and 

 stones, and have even carried brushwood, bones, and the nest of a 

 land-bird, it can hardly be doubted that they must occasionally, 

 as suggested by Lyell, have transported seeds from one part to 

 another of the arctic and antarctic regions ; and during the Glacial 

 period from one part of the now temperate regions to another. 

 In the Azores, from the large number of plants common to 

 Europe, in comparison with the species on the other islands of the 

 Atlantic, which stand nearer to the mainland, and (as remarked 

 by Mr. H. C. Watson) from their somewhat northern character in 

 comparison with the latitude, I suspected that these islands had 

 been partly stocked by ice-borne seeds, during the Glacial epoch. 

 At my request Sir C. Lyell wrote to M. Hartung to inquire 

 whether he had observed erratic boulders on these islands, and he 



