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Show GEOGRAPHICAL DISTRIBUTION. [CHAP. XI. 312 plants and for many animals during thei~ migration. In the coral-producing oceans such sunken 1slands are now marked as I believe by rings of coral or atolls standing over th~m. Whenev'er it is fully admitted, as I believe it will some day be, that each ~pecies has proc~eded from a single birthplace, and when m the course of. tui_Ie w~ know something definite about the means of d1Btnbut10n, we shall be enabled to speculate with security on the former extension of the land. But I do not believe that it will ever be proved that within the recent period continents which are now quite separate, have been continuously, or almost continuously, united with each other, and with the many existing oceanic islands. Several facts in distribu-tion,- such as the great difference in the marine faunas on tlie opposite sides of almost every continent,-the close relation of the tertiary inhabitants of several lands and even seas to their present inhabitants,-a certain degree of relation (as we shall hereafter see) between the distribution of mammals and the depth of the sea,-these and other such facts seem to me opposed to the admission of such prodigious geographical revolutions within the recent period, as are necessitated on the view advanced by Forbes and admitted by his many followers. The nature and relative proportions of the inhabitants of oceanic islands likewise seem to me opposed to the belief of their former continuity with continents. Nor does their almost universally volcanic composition favour the admission that they are the wrecks of sunken continents ;-if they had originally existed as mountain-ranges on the land, some at least of the islands would have been formed, like other mountain-summits, of granite, metamorphic schists, old fossiliferous or other such rocks, instead of consisting of mere piles of volcanic 1uatter. I must now say a few words on what are called acci-dental means, but which more properly might be called occasional means of distribution. I shall here confine myself to plants. In botanical works, this or that plant is stated to be ill adapted for wide dissemination; but for transport across the sea, the greater. or less facilities may be said to be almost who~ly u.nimown. Until I tried, CHAP. Xi.J MEANS OF DISPERSAL with Mr. Berkeley's ·a . 313 even known how far aid, a few experiments . of sea-water. To see s co?-ld resist the inj' I~ was ::'-ot kinds, 64 germinat.:Yaft~;:rms~ I found tha~n~:: aftion a few survived an · .an Immersion of 28 d 0 8'7 ience sake I chiefl ~~mersiOn of 137 days F ays, and or fruit; and as afi ofi~~ small seeds, with~ut tb.r convennot be floated across . :J.se sank in a few days th capsule not they were in. ur WI e spaces of the sea ' ey could tried some largej f e~ by the salt-water Af~hether or floated for a Ion . rm s, capsules, &c a~d erwards I there is in the gb~:e. It is well kno;n wh!~md·% these and it occurred to nieailiyt oflf gdreen. and season:d \. erbence or branch d a oo s might h Im er; and then hi :fres~~~~s!hi~~higtht be d:7:J 0~~~~ [~~Its sea. Hence I was I d e s ream be washed . rs, ~nts ~t~ ripe frui~, a!d d:J s~ems and branch~:t~f t~~ 11o:t:_aJ~::t~ ~~ ;h~~~~, bu?s~:e t~hicho~h~:t water. ~~~~ foJ _instance, ripe I~:J-!~~ dried ~oated ~~~h when pi~nt;~e~h!hyey flo~ted for 90 ~:ya~l~ndmamftediately, ri b · ~erm1nated · erwards 85pe erries floated for 23 d ' an asp~ragus plant with days, and the d ays, when dned it ii " fl~edtsdof..,Heloscia~:Uss:!~:~rds germinated: o~:drfpo~ a e lOr above 90 d wo days, when dried -:f~gether out of the 94 JJ~;nt afterwards germin:feJ P erioals, asnd some of the 18 flort:~s, 18 floated for abov~ . · o that as 6 4 1or a very mu h 1 swn of 28 days . anda7 seeds germinated aftei1 c . onger all th ' as .!.!'.pia t . . an Immer-after b:htme s~ecies as in t'he for~ ~h:Ith npe. fruit (but not anythin i dried, for above 28 d~ s g experiment) floated, the seJs :£~ ,these scanty factsy .;.:s ~ar as we may infer by sea-curren~od.J~~ngts 2~f dany c~untry ~;h~~~~ tfadt pavoewrear~ eo f genni . ays, and would . oa e rate ta~IOn. In Johnston's Ph . ritaln their per diem (s o t e several Atlantic cu yswa. Atlas, the per diem). ~meth·urrents running at th:;:entts Ifs 33 miles Iongin to' n IS average, the seed ra eo 60 miles ~4 one country might be flo at se dofa ciroo4os s p9l2a4n tms iblees |