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380
HENNING HORN AF RANTZIEN
cvcr lakes place. The vegetation of Ihe aerohalinous belt, however.
is at all times exposed lo a certain supply of atmospheric salt, i.e. salt
particles which by the agency of sea-breezes are carried in over land
and deposited there. Consequently, as the species occnrs both within
the salt-affected aerohalinous belt and also within that bv salt unaffected
ahalinous belt, we must come to the conclusion, recently emphasized
by englund (1942, p. 100 ff.), that Phl. arenarium is indifferent as
regards salt. However, in connection with this, it should he remarked
that the material value of the sali supply in the aerohalinous belt has
been discussed and that the discussion has led lo rather lieterogeneous
conclusions (cf. e.g. Frödin 1912, p. 60, HÄYREN 1914, pp. 15—16,
Kearney 1904, pp. 428—432 and Warming 1906, p. 291).
Study of the distribution maps has shown that Phl. arenarium is
in the main in a striking way conl’ined to the neighbourhood of the
coasls. This facl mav in particular be due to two reasons. One is that
the species in question is a confirmed lover of sand and is thereby
bound to drifting, dune-forming sand. the otlier that it seems to be
found only in districts characterized by an oceanic type of climate.
Being a psammophyte, however, it scarcely belongs to the most
extreme types, and it appears very rarely as a constituent of the
vegetation ön the most strongly pronounced driftsand dunes (cf. Warming
1891 and 1907 —09, also Warming and Graebner 1918). Massart points
out (1912, pp. 73 and 111) that in Belgium this species is commonly
met with ön all dunes where the sand has been fixed by vegetation,
particularly together with such species as Ammophila arenaria,
Corij-nepliorus canescens, Carex arenaria, Silene conica. Iasione montana and
Brachi/thecium albicans. Preuss (1911. p. 170 ff.) emphasizes that Phl.
arenarium at the southern coast of the Baltic is fairly tolerant. As a
matter of fact, though il scarcely ever appears ön Ihe windward sides
of the drifting sand-dunes, it alreadv begins to make ils appearance ön
the open sandy ground in the lee of the dunes. Within bis district of
investigation, according to Preuss, il reaches its optimum ön those
dunes which he classifies as »Übergangsdünen», i.e. driftsand-dunes
where ground condensation and humus formation have alreadv begun
to set in to a rather high degree, but which have not yet arrived at the
characteristic State of »grev dunes». Preuss (I.e., p. 176) gives an
interesting example of the coloniale vegetation |the term »coloniale»
is here taken in the sense of Weaver and Clements (1929. p. 53);
n o t Jackson (1928. p. 85): »colonial») ön a dune of this kind
(Barsh-beker See at Kiel). He mentions among otliers Phl. arenarium, Scleran-
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