MEANS OF DISPERSAL. 363 



days they slowly careered round and round in an immense 

 ellipse, at least five or six miles in diameter, and at night 

 alighted on the taller trees, which were completely coated 

 with them. They then disappeared over the sea, as suddenly 

 as they had appeared, and have not since visited the island. 

 Now, in parts of Natal it is believed by some farmers, 

 though on insufficient evidence, that injurious seeds are 

 introduced into their grass-land in the dung left by the great 

 flights of locusts which often visit that country. In conse- 

 quence of this belief Mr. Weale sent me in a letter a small 

 packet of the dried pellets, out of which 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 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. Swaysland, of Brighton, who during the 

 last forty years has paid close attention to our migratory 

 birds, informs me that he has often shot wagtails (Mota- 

 cillae), 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, Professor 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 : these consisted of twelve 

 monocotyledons, including the common oat, and at least one 

 kind of grass, and of seventy dicotyledons, 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 



