Chap. XI. MEANS OF DISPERSAL. 361 



stones for their tools, solely from the roots of drifted 

 trees, these stones being a valuable royal tax. I find 

 on examination, that when irregularly shaped stones 

 are embedded in the roots of trees, small parcels of 

 earth are very frequently enclosed in their interstices 

 and behind them, — so perfectly that not a particle 

 could be washed away in the longest transport : out of 

 one small portion of earth thus completely enclosed by 

 wood in an oak about 50 years old, three dicotyle- 

 donous plants germinated : I am certain of the accuracy 

 of this observation. Again, I can show that the car- 

 casses of birds, when floating on the sea, sometimes 

 escape being immediately devoured; and seeds of 

 many kinds in the crops of floating birds long retain 

 their vitality : peas and vetches, for instance, are killed 

 by even a few days' immersion in sea- water ; but some 

 taken out of the crop of a pigeon, which had floated on 

 artificial salt-water for 30 days, to my surprise nearly all 

 germinated. 



Living birds can hardly fail to be highly effective 

 agents in the transportation of seeds. I could give 

 many facts showing how frequently birds of many kinds 

 are blown by gales to vast distances across the ocean. 

 We may I think safely assume that under such circum- 

 stances their rate of flight would often be 35 miles an 

 hour ; and some authors have given a far higher esti- 

 mate. I have never seen an instance of nutritious 

 seeds passing through the intestines of a bird; but 

 hard seeds of fruit will pass uninjured through even 

 the digestive organs of a turkey. In the course of two 

 months, I picked up in my garden 12 kinds of seeds, 

 out of the excrement of small birds, and these seemed 

 perfect, and some of them, which I tried, germinated. 

 But the following fact is more important : the crops of 

 birds do not secrete gastric juice, and do not in the 



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