Rit Landbúnaðardeildar : B-flokkur - 01.05.1947, Síða 13

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observed on the shores of the Azores. At the Great Lakes of America the
type of C. edentula on the beach belongs to the ssp. lacustris (Fern.)
Hultén, but the forms growing in West-America are named ssp. cali-
fornica (Fern.) Hultén.
The European species C. maritima is found at the beaches of Europe
from North-Scandinavia and the Baltic Sea soutli to the Mediterranean
and North-Africa. It also is observed at the Black Sea and the Persian
Gulf as well as in the Faeroes and Spitzbergen.
5. Discussion.
The species Cakile edentulix was originally distinguished from the
Linnaean species C. maritima on the basis of its morphological character-
istics. Phytogeographical observations were found to give a very good
support to the taxonomical understanding of the species. The results
obtained by the present writers demonstrate that a sterility barrier must
be found between the both species, as the European C. maritima is diploid
but the species C. edentula tetraploid. On the basis of the cytological
results it is suggested that the latter species should be regarded as an
autotetrapioid type.
By far the most interesting' question in connection with the present
investigation is the dispersion of the species to Iceland. As almost nothing
has been written about the origin of the Icelandic flora some discussion
on the basis of the present investigation as well as other investigations
made by the present and previous writers might be of some interest.
As yet, the problems of the origin of the Icelandic flora have not been
studied thoroughly. Most of the older scientists seem to have taken it
for granted that all the species found at present on the island had
dispersed from other countries after the iast glaciation (cf. Thoroddsen>
1914; Stefánsson, 1913, 1920; Stefánsson and Steindórsson, 1937,
1946). During the last decades, however, some scholars have assuined a
possible survival of at least a few species during the latest glaciation
(Lindroth, 1931; Gelting, 1934; Steere, 1937; Steindórsson, 1937;
Thorarinsson, 1937; Löve and Löve, 1943; Löve, 1947). Of course, these
assumptions have been influenced by the studies on surviving species of
Scandinavia (cf. Hansen, 1904, 1930; Fries, 1913; Nordhagen, 1932, 1933,
1935; Nannfeldt, 1935, 1940; Holmboe, 1937; Björkman, 1939; Du Rietz,
1942; Hasselrot, 1935, 1941; Samuei.sson, 1943; Arwidsson, 1943).
Last summer the present writers began an investigation of the origin
of the Icelandic flora elements. The present paper is the first publication