362 DARWINISM 



a very small portion of mud may serve to convey seeds, and 

 such an occurrence repeated even at long intervals may greatly 

 aid in stocking remote islands with vegetation. Many seeds 

 also adhere to the feathers of birds, and thus, again, may be 

 conveyed as far as birds are ever carried. Dr. Guppy found 

 a small hard seed in the gizzard of a Cape Petrel, taken about 

 550 miles east of Tristan da Cunha. 



Dispersal of Seeds by the Wind. 



In the preceding cases we have been able to obtain direct 

 evidence of transportal ; but although we know that many seeds 

 are specially adapted to be dispersed by the wind, we cannot 

 obtain direct proof that they are so carried for hundreds or 

 thousands of miles across the sea, owing to the difficulty of 

 detecting single objects which are so small and inconspicuous. 

 It is probable, however, that the wind as an agent of dispersal 

 is really more effective than any of those we have hitherto 

 considered, because a very large number of plants have seeds 

 which are very small and light, and are often of such a form 

 as to facilitate aerial carriage for enormous distances. It is 

 evident that such seeds are especially liable to be transported 

 by violent winds, because they become ripe in autumn at the 

 time when storms are most prevalent, while they either lie 

 upon the surface of the ground, or are disposed in dry capsules 

 on the plant ready to be blown away, If inorganic particles 

 comparable in weight, size, or form with such seeds are 

 carried for great distances, we may be sure that seeds will also 

 be occasionally carried in the same way. It will, therefore, 

 be necessary to give a few examples of wind-carriage of small 

 objects. 



On 27th July 1875 a remarkable shower of small pieces of 

 hay occurred at Monkstown, near Dublin. They appeared 

 floating slowly down from a great height, as if falling from a 

 dark cloud which hung overhead. The pieces picked up were 

 wet, and varied from single blades of grass to tufts weighing 

 one or two ounces. A similar shower occurred a few days 

 earlier in Denbighshire, and was observed to travel in a 

 direction contrary to that of the wind in the lower atmosphere. 1 

 There is no evidence of the distance from which the hay was 

 1 Nature (1875), vol. xii. pp. 279, 298. 



