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STUDIES IN PH LE UM ARENARIUM
379
examples. A very interesling lac| in lliis conneclion is the strikinglv good
accordance between the maps of the total distribution of Piil. arenarium
and the lichens Lobaria laetevirens, Nephroma lusitanicum and
Parme-liella plumbea (cl. Degelius I.e.. Figs 1(5, 18 and 30). These lichens
are referred to the northern Mediterranean-montane suboceanic species.
Degelius himself has 1’ound no representatives of this distribution group
among bryophytes and vaseular plants; lie mentions some cormophytes
hut emphasizes that they cail hardlv be considered as representative.
The similarity between the distribution of Piil. arenarium and that
of the lichens in question is very interesting but il seems to be
inappro-priate to draw too extensive conclusions from the facts above.
Distribution is a rather complicated phenomenon with a great multitude of
factors involved, and it can be rather dangerous to state a near
connec-tion between two biologieal distribution maps with an outer similarity.
In the present question il is difficult to draw any conclusions from the
remarkable resemblance emphasized above. At present we can only
establish the fact that there i s a resemblance. Thus its significance for
the interpretation of the plant geographical problems associated with
Piil. arenarium is unknown.
From what precedes it will be seen that Phl. arenarium is a M
e-d i t c r r a n e a n and Atlantic species with its distribution centre
in the west of Central Europé.
In the following some of those factors are discussed which could
have a determinative influence ön the development of t Ii is distribution,
above all the relation of the species to salt, sand, linie and climate.
4. Some Ecological Features of Special Significance
for the Distribution.
The great majority of known localities of Phl. arenarium are
siluated ön or near the sea-shores. Records from the inland, partly
stated from districts which are far awav from the sea, are known
however. It is evident both from direct observation of nature and from
statenients in the literature (e.g. Englund 1942, Erikson 1896,
Kühn-holtz-Lordat 1923, .Massart 1912. Preuss 1911 and Sterner 1938)
that the sea-shore localities are situated within the aerohalinous and
ahalinous hclts (cf. Du Rietz 1925, p. 53 and 1932. p. 85), consequently,
according to the latest terminology, within the eugeobiontic zone (cf.
Du Rietz 1940. pp. 106- 107), where no inundation by waves or sprays
25 Botaniska Xoliser WiC.
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