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, 
les 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! 
who writes: ,[t 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. ¢., 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 water 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- 
1) Ernst, A., The New Flora of the Voleanic Island of Krakatau. Cambridge 1908. 
