PROBLEMS OF DISTRIBUTION AND THEIR SOLUTION. 165 



next, act as efficient transporters of seeds. The hard seeds of many 

 fruits pass uninjured through the digestive system of birds, and 

 germinate thereafter. Even when a bird, containing seeds in its 

 digestive system, has been swallowed by a hawk or other bird of 

 prey, the seeds may be preserved intact during this double intus- 

 susception, and, on being disgorged by the flesh-eater, may germinate. 

 " Seeds of the oat, wheat, millet, canary, hemp, clover, and beet, 

 germinated after having been from twelve to twenty-one hours in 

 the stomachs of different birds of prey; and two seeds of beet 

 grew after having been thus retained for two days and fourteen hours." 

 As regards insects, locusts, says Darwin, " may be blown to great 

 distances from the land." A locust was caught 370 miles from the 

 coast of Africa. In November 1844, a swarm of locusts visited 

 Madeira, and Darwin remarks that, as from locust-dung he extracted 

 the seeds of seven grass plants, " 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." 

 More curious still is it to discover a means of plant-dispersal in the 

 earth which adheres to the beak and feet of birds. From the leg of 

 a woodcock, a little cake of dry earth weighing nine grains was 

 removed by Mr. Darwin. In this earth a seed of the toad-rush was 

 contained, and this seed germinated. From the seeds contained in 

 the earth adhering to the leg of a partridge, which had been 

 kept for three years, Mr. Darwin obtained 82 plants. ''With such 

 facts before us," says Mr. Darwin, " 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 Mediterranean must occasionally transport a few seeds 

 imbedded in dirt adhering to their feet or beaks?" The agency 

 of icefloes and icebergs, which are frequently laden with earth, and 

 which have been known even to transport the nest of a land bird, 

 must likewise be considered as a means whereby transport of arctic 

 and antarctic species may have occurred. We must lastly add to 

 these artificial methods of plant-dispersal, the natural means which 

 exist in many plants for the diffusion of their offspring. Winged 

 seeds and fruits are by no means uncommon; the pappus or down 

 of the dandelion and other Composite present familiar examples of 

 natural contrivances for securing a wide distribution of their seeds ; 

 there are some flower-heads (Accena] which adhere to the fur of 

 animals or to the feathers of birds like our familiar "burrs"; and 

 other plants, again, possess more special contrivances still for securing 

 their adhesion to the animal integument. 



The dispersal of animals in the same way is accomplished by 

 natural and casual means. The power of flight and of swimming 

 illustrate the former ; whilst the conveyance of an animal on drift- 



