MEANS OF DISPERSAL, 337 



sea, as suddenly as they had appeared, and luive not since 

 visited the island. Now, in parts of Natul it is believed by 

 some farmers, though on insufficient evidence, thai injuri- 

 ous seeds are introduced into their grass-land in the dung 

 left by the great flights of locusts which often visit that 

 country. In consequence of this belief Mr. Weale sent me 

 in a letter a small packet of the dried pellets, out of wliich 

 I extracted under the microscope several seeds, and raised 

 from them seven grass plants, belonging to two species, of 

 two genera. Hence a swarm of locusts, such as that 

 which visited Madeira, might readily be the means of in- 

 troducing 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 arg:illaceous 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 germin- 

 ated and flowered. Mr. Swaysland, of Brighton, who dur- 

 ing the last forty years has paid close attention to our 

 migratory birds, informs me that he has often shot wag- 

 tails (Motacillae), wheatears, and whinchats (Saxicoht), 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 cliarged with seeds. For instance, 

 Prof essor Newton sent me the leg of a red-legged partridge 

 (Caccabis rufa) which had been wounded and could not 

 fly, with a ball of hard earth adhering to it, and weighing 

 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 eighty-two plants sprung from it: those 

 consisted of twelve monocotyledons, including the common 

 oat, and at least one kind of grass, and of seventy dicotyle- 

 dons, which consisted, judging 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 an- 



