110
THE ESSEX NATURALIST.
pollen-flora of the "praeboreal" "niveau 89" in Halland
(peat mosses Nos. 4, 7, 8, 21, 35, 36, 42, 54a).
Figs. 1 D., 1 E., and 1 F., on the other hand, show spectra
which we must consider as being somewhat younger than the
moorlog spectrum. 1 D. is a probably "boreal" spectrum from
Northern Scotland (Ross-shire) and the outlying islands ; 1 E.
is a late "boreal" spectrum from Halland ("niveau 61" of
the peat-mosses Nos. 4, 5, 10, 24, 35, 36, 38 and 54). Fig. 1 F.
shows a spectrum from the oldest Danish Stone Age (the Mullerup
culture), calculated on the percentage figures from four samples
from the peat-mosses, Svaerdborg Mose and Mullerup Maglemose,
published by Knud Jessen ("Bog-investigations in North East
Sjaelland."—Danmarks Geol. Unders., Ser. ii., No. 34, 1920).
The moorlog specimens are certainly older than the Magle-
mose culture or, according to the Geo-chronology of Gerhard
De Geer, about 9,000 years old.
It is to be regretted that no spectra are available from Jutland,
the Netherlands, or the Norfolk-Suffolk coast. Such spectra
would probably give a clue to the determination of the real age
of the moorlog. In default of these we have to make a com-
parison with more distant countries, such as Scotland, Sweden
and Denmark (Sjaslland).
In these countries, so far as is known, birch pollen is the
prevailing one in deposits of "praeboreal" age. Pollen grains
of pine and of species of willow occur in a minor degree ; pollen
grains of hazel, alder, oak, elm, lime, etc., are totally absent.
They appear, however, in the older "boreal" deposits, where
pollen of pine dominates and where the frequency of hazel pollen
often shows a rapid increase (cf. von Post in Geol. Foren. Fork.,
Bd. 46, p. 124, 1924)
Bearing in mind these facts, as illustrated in the figs. 1 B.-F.,
it seems most probable that the moorlog was formed in the
transitional period between "praeboreal" and "boreal" times,
or during the very first phase of the latter (compare especially
the very close relation of fig. 1 A. to fig. 1B.). The specimens are
much decayed, commonly black and very compressed, almost
like brown coal. Their P.F. (pollen frequency per sq. cm. of
the preparations) is strikingly low, which may perhaps indicate
a scanty and scattered forest vegetation during their formation.