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Show DISTRIBUTION. [CRAP. XI. GEOGRAPIIIC.AL 314 d hen stranded, if blown f Sea to another coun t r y.' a. n1 wd gale they wonl d ger- oto a favourable spo t by an In an ' . mi· nat e. expen·m ent s ' }'I · 1fartens tned 1 1 d Subsequently .to Jny h b ttor manner, for le p ace s.n ni. lar ones, but In .a rothuoe acteu al sea, so that the·y w.e re tho seeds in a box 1~ ed to the air like real1y floa~Ing alternately wet. and exposd mostly differe~t froin mine ; lants. lie tned 98 s.ee s~·uits and likewise seeds from tnt he chose ~any lai~e t~e sea ; and this would ha~e plants which hve n~ar th of their flotation and of then favoured the aver~g~ ~n~s action of the salt-water. On resistance to the llnJ~~do ot previously dry the l)lants or the other hand le . ?- n d this as we have seen, would branches with the frui\; an t h~vo floated much longer. have caused some of lt slCf h~s seeds floated for 42 days, The result was that '\~ ~f ennination. But I do not and were then capab t g the waves would float for a doubt that plants exposetd to d from violent Inovement as less time th~n those lf~e:~f;re it would perhaps be sar,er in our experiments. d f bout _1_o_ plants of a fio1a, to assume that the s~e s o hl be ftooated across a space after having b.een ~ried_,d~~u and would then germinate. of sea 900 miles In WI. ' ft n ftoatin()' longer than the The fact of the l~rger fnut~ o t e with lar~·e seeds or fruit sJnall, is interesting ; as ~ea: ~ any oihor means ; and could hardly be transpohr .fhat such plants generally Al h. de Candolle has s own ha~e restricted ranges. . lly transported in another But seeds may be o?cas1ona n u on rnost islands, even manner .. Drift t~mber l~l~h~~~st o~eans; and the nativ~~ on those 1n the mids~ oft aci:fic rocure stones for then of the coral-islands In the p f d :.fted trees those stones tools, solely from the roots o I fl~d on exal~ination, that being a valuable royal tax. embedded in the roots when irregularly shaped stones are fro uently enclosed of trees, small p~rccls 0~ e~rih: ade tit~~ -io pcrf'ect1y that in their interstices an e~ud ay in tho longest transnot a particle could b\iwas ~ :~f earth thus completely lJort . out of one sma por 110 b t 50 years old, three enclo·s ed by woo d m· an oa r a ou CHAP. XI.] MEANS OF DISPERSAL. 315 dicotyledonous plants germinated: I am certain of the accuracy of this observation. Again, I can show that the carcasses of birds, when floating on the sea, son1etimcs e~cape. being im1ncdiately deyoure~- ; and seeds of many .. kinds 1n the crops of floating bnds long retain their vitality: peas and vetches, for instance, are killed by even a few days' immersion in sea-water; but son1e 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 circumstances their rate of :flight would often be 35 miles an hour ; and some authors have given a far higher estimate. 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, 1 picked up in my garden 12 kinds of seeds, out of the excrement of s1nall birds, and these seemed perfect, and some of then1, which I tried, germinated. But the following fact is more ilnportant : the crops of birds do not secrete gastric juice, and do not in the least injure, as I kno'v by trial, the germination of seeds; now after a bird has found and devoured a large supply of food, it is positively assorted that all the grains do not pass into the gizzard for 12 or even 18 hours. A bird in this interval might easily be blo·wn to the distance ,)~ 500 miles, and hawks are known to look out for tired bird~, and the contents of their torn crops might thus readily get scattered. Mr. Brent inforn1s 1ne that a friend of his had to give up :flying carrier-pigeons from France to England, as the hawks on the English coast destroyed so ~nany on their arrival. Some hawks and owls bolt the1r prey whole, and after an interval of from twelve to tw~nty hours, disgorge pellets, which, as I know fro1n expenments made in the Zoological Gardens include seeds capable of germination. Some seeds of the oat wheat . ' ' |
