Rit Landbúnaðardeildar : B-flokkur - 01.05.1947, Page 16

14
(1930) agree with the above-mentioned authors in concluding that the
wind would only be able to carry the piumed seeds a relatively short
distance. Last hut not least, Wulff (1943) is of the opinion that “the
wind is a very important factor in the dissemination of seeds over short
distances but has little significance in their transport over long distances,
and that, consequently, most discontinous areas cannot be explained by
its action.“
As regards the Icelandic flora, the present writers are inclined to
regard it as a very distant possibility that some few of the present species
have dispersed from other countries to the island in recent times by the
help of air currents. Pollen analytical studies on peat in the Faeroes
indicate that at least pollen grains might have been carried by the wind
from Scotland or Noi’way to the Faeroes after the last glaciation (Jessen
and Rasmussen, 1922) and, thus, it is not fully excluded that pollen and
small seeds rnight occasionally be carried by the wind from Europe to
Iceland, especially if the winds in the North Atlantic were not of the same
type as at present when the last glaciation ended. The present North
Atlantic air currents, however, almost wholly contradict that hypothesis,
as shown, e.g. by Birkeland and Föyn (1932), Lindroth (1931) and
Thoroddsen (1914). Observations on the distribution of vulcanic ash
fronx Iceland indicate, too, that the dispersion by air currents would
mainly be from west to east, but not vice versa.
Although some few species might, theoretically, have been dispersed by
the wind to Iceland frorn Greenland or the American continent, studies on
their distribution in Iceland and Greenland seem to indicate that their
number might not exceed the number of the fingers on the left hand
(cf. Ostenfeld, 1926). Most of the Icelandic species are closely related
to the species of Northern Scandinavia and Scotland, but only a very little
part of the flora is of American origin.
Concerning the possibilities of dispersal of seeds by hirds, almost all
critical observations made by different scientists seem to indicate that
birds most probably are not able to transport seeds across oceans,
although they may be able to disperse seeds over wide areas (Birger, 1907;
Borza and Bujorean, 1927; Darwin, 1859; Docters van Leeuwen, 1934;
Fischer, 1931; Heintze, 1932—1936; Hemsley, 1885; Jennings, 1933;
Kerner, 1898; Metsavainio, 1926; Sargent, 1928; Simpson, 1932; Winge,
quoted from Schröter, 1934; Zazhurilo, 1931). Most birds come to Ice-
land from Scotland and Ireland in spring, when practically no fresh seeds
are found in nature, and the fact that the great majority of the Icelandic
species are most closely related to the flora elements of North Scandinavia
might possibly be taken as an evidence showing that birds are not able to