496 MR. G. ERDTMAN: STUDIES IN THE 
9. Quercus. Oak-pollen, which plays an important part in the pollen-flora 
of S. Sweden, N.W. Germany, cte., exhibits no interesting features in 
Scotland. It oceurs to about the same extent (2-5 per cent.) in all the 
districts investigated. Above the A-zone it usually hasa greater percentage 
than elm-pollen, below it elm-pollen is the most frequent. Only very rarely 
are percentages up to 10, 15, or 20 met with. In Denmark and Sweden oak- 
pollen is found belonging to the oldest Neolithic Age. 
10. Tilia. 9 pollen-grains were found: 4 from Achnasheen, 3 from the 
Shetlands, 1 from Skye, 1 from Helmsdale. Jessen and Rasmussen (1922 
found 1 lime-pollen grain in the Faroes. In Sjælland and Sweden it occurs 
much more abundantly. Its first appearance, as that of the elm, dates from 
late boreal time (“the Mullerup period "). 
11. Ulmus. Elm-pollen has the same occurrence as oak-pollen, but its 
highest percentage occurs at an earlier period than that of the oak. Its 
mean frequency is exactly half that of the oak. In the peat mosses of 
South and Middle Sweden the frequency is greater, but only in exceptional 
cases does the percentage reach 15 and up to 36 (cf. Halden, 1917, 
p- 143). 
5. THE CHARACTER OF THE PosTGLACIAL WOODLANDS OF SCOTLAND AND 
SOME OTHER COUNTRIES AS SUGGESTED BY THE STATISTICAL METHOD 
OF PoLLEN RESEARCH. 
If the sum of all pollen-grains (14,843) recorded in the above analyses 
is taken, and the percentages of the different species of pollen is then 
calculated, we get a sort of general pollen-spectrum giving us an idea of the 
forest character of N. Scotland and the Isles in postglacial times. The 
percentage figures are as follows :— 
Betula 70 per cent. 
Pinus — 14:6 per cent. 
Alnus 118 per cent. 
Quercus 2'4 per cent. 
Ulmus 1:2 per cent. 
Acer, Carpinus, Fagus, Frazinus?, Hex, Tilia only traces. 
(Corylus 4'25 per cent.) 
(“ Salix ” 11:25 per cent.) 
This spectrum is shown diagrammatically in text-fig. 20, and for com- 
parison the general spectrum of the A-zone is shown in No. 9. These 
diagrams for several reasons, however, are only very approximate. We 
do not know, for instance, with the accuracy that could be desired, how 
the area of the pollen-producing forests reacts upon, and is related to, the 
fossil pollen-Hora. A first attempt to solve this question by direct 
observation was made by the author (1921). The forests in a district of 
