430 ORIGIN OF SPECIES 



ately to acquire, as if in consequence, a wide range. I think 

 favourable means of dispersal explain this fact. I have be- 

 fore mentioned that earth occasionally adheres in some quan- 

 tity to the feet and beaks of birds. Wading birds, which 

 frequent the muddy edges of ponds, if suddenly flushed, 

 would be the most likely to have muddy feet. Birds of this 

 order wander more than those of any other; and they are 

 occasionally found on the most remote and barren islands 

 of the open ocean; they would not be likely to alight on the 

 surface of the sea, so that any dirt on their feet would not be 

 washed off; and when gaining the land, they would be sure to 

 fly to their natural fresh-water haunts. I do not believe that 

 botanists are aware how charged the mud of ponds is with 

 seeds; I have tried several little experiments, but will here 

 give only the most striking case: I took in February three 

 table-spoonfuls of mud from three different points, beneath 

 water, on the edge of a little pond: this mud when dried 

 weighed only 6}i ounces; I kept it covered up in my study 

 for six months, pulling up and counting each plant as it 

 grew; the plants were of many kinds, and were altogether 

 537 in number; and yet the viscid mud was all contained in 

 a breakfast cup ! Considering these facts, I think it would 

 be an inexplicable circumstance if water-birds did not trans- 

 port the seeds of fresh-water plants to unstocked ponds and 

 streams, situated at very distant points. The same agency 

 may have come into play with the eggs of some of the 

 smaller fresh-water animals. 



Other and unknown agencies probably have also played a 

 part. I have stated that fresh-water fish eat some kinds of 

 seeds, though they reject many other kinds after having 

 swallowed them; even small fish swallow seeds of moderate 

 size, as of the yellow water-lily and Potamogeton. Herons 

 and other birds, century after century, have gone on daily 

 devouring fish; they then take flight and go to other waters, 

 or are blown across the sea; and we have seen that seeds 

 retain their power of germination, when rejected many hours 

 afterwards in pellets or in the excrement. When I saw the 

 great size of the seeds of that fine water-lily, the Nelumbium, 

 and remembered Alph. de Candolle's remarks on the distribu- 

 tion of this plant, I though that the means of its dispersal 



