16 H. G. SIMMONS. [SEC. ARCT. EXP. FRAM 



of this discussion, viz., marine currents and floating ice. The cause for 

 excluding this as a factor in the stocking of the islands here in question, 

 lies partly in the existence of a high ice-foot round most parts of their 

 shores. Castle Island was entirely encircled by an icefoot which appeared 

 never to disappear, and, even had some part of the ice-foot along the 

 shore of Devil's Isle been washed away at the time of our visit, I 

 think that no single species has reached thither with the help of the 

 water. The influence of marine currents in the dispersal of plants has 

 certainly been often much over-valued, and I can only agree with ERNST 1 

 who writes: r lt has long been known that only a comparatively small 

 proportion of plants are capable of extending the area of their distri- 

 bution by this means. A comparison of island floras has shown that it 

 is exclusively strand plants which have seeds and fruits posses- 

 sing the necessary adaptations for this method of dispersal by ocean- 

 currents, that is which are capable of floating for weeks or months on 

 sea- water, without losing the power of germination" (1. c i( p. 5). 



But here we have not a single strand plant, and, as a rule, the 

 arctic lands are rather poor in halophytic plants which might stand a 

 journey in salt water. The floating ice, of course, may sometimes carry 

 seeds and fragments of plants I have occasionally seen blocks of ice 

 from the tidal crack, laden with masses of vegetable matter - - but this 

 does not prove that plants can in fact immigrate by that means of 

 conveyance; for a short drift within a fjord or over a strait, it may 

 perhaps sometimes be of use, if the ice-block takes the shore again 

 before the plant fragments are blown into the w^ter or wetted through; 

 but as a transport over wide distances it is certainly not serviceable, as 

 the vegetable matter will be imbedded in the ice and will be unable to 

 come farther inland before being immersed in salt water. 



It may also be mentioned that both islands were formerly visited 

 by man. I am not, indeed, inclined to attribute any influence for the 

 transporting of plants to these visits, but where people have been, one 

 has always the possibility of human influence to reckon with. The 

 indication of human visitors to these islands consisted especially in a 

 sort of shelters, built for the eider-ducks to place their nests in. Now 

 such shelters are built in countries where the eider-duck is protected 

 for the collecting of down; but it is not known that the Eskimo have 

 done any such thing anywhere else, and this region has certainly never 

 had any other human inhabitants. Perhaps the shelters may be attri- 



ERNST, A., The New Flora of the Volcanic Island of Krakatau. Cambridge 1908. 



