Chap. XII.] MEANS OP DISPEESAL. I47 



ment; and several of these seeds retained the power of 

 germination. Certain seeds, however, were always 

 killed by this process. 



Locusts are sometimes blown to great distances from 

 the land; I myself caught one 370 miles from the coast 

 of Africa, and have heard of others caught at greater 

 distances. The Eev. E. T. Lowe informed Sir C. Lyell 

 that in November 1844 swarms of locusts visited the 

 island of Madeira. They were in countless numbers, as 

 thick as the flakes of snow in the heaviest snowstorm, 

 and extended upwards as far as could be seen with a 

 telescope. During two or three days they slowly ca- 

 reered round and round in an immense ellipse, at least 

 five or six miles in diameter, and at night ahghted 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. N"ow, in parts of Natal it is beUeved 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 consequence 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 

 85 



