MICROPALÆONTOLOGY OF POSTGLACIAL DEPOSITS. 495 
4. Carpinus. Only two pollen-grains from Orkney deposits have been 
identified with certainty as belonging to the hornbeam. Only small 
quantities of the pollen of this tree have been recorded in Sjælland and 
S.W. Sweden, showing that its immigration occurred during the sub-boreal 
period. 
5. Corylus. Although not a forest tree sensu stricto it will be briefly 
considered here. The highest frequency for hazel-pollen is found about the 
A-zone. Also in Sweden it has its maximum occurrence in very old (boreal) 
layers, a subject studied very thoroughly by von Post (1916). It is probable 
that this behaviour will prove to bea salient feature in the mosses of North 
and Middle Europe (ef. e. 4. Rudolf and Firbas, 1923; Stark, 1923). 
6. Fagus. Only 3 pollen-grains were met with: 1 from Shetland, 1 the 
Orkneys, and 1 from Lewis. 
(65. Fraxinus. Pollen resembling that of Fravinus was seen, but the 
determination was uncertain.) 
7. Dex. Pollen-grains, in all 5, were obtained from the same places as 
the beech-pollen. 
8. Pinus. It is a most striking fact that pine-pollen occurs in practically 
all samples in which birch-pollen occurs. In the oldest part of the Shawbost 
gyttja (Lewis) birch-pollen is lacking and pine-pollen too. It is possible, 
however, that much of the pollen may have been transported a great 
distance by the wind, and that in consequence we have no reliable evidence 
as to the distribution of pine in the earliest postglacial times. At the 
A-zone period the great percentage of pine-pollen, the presence of fragments 
of leaf epidermis, and in places of great trunks and stools, prove that pine 
grew in Ross-shire. High pollen-percentages from the Outer Hebrides (46, 
32, 30 per cent., ete.) make it very probable that pine also grew there at the 
same time. J. Geikie (1867) tells of pine-remains from these islands, but 
without definite description of the localities. As the A-zone seems to be of 
a very considerable age—I think it is most probable that it should be 
correlated with the boreal of the Scandinavian peat-geologists—pine forests 
must have covered parts of Scotland at a much earlier time than Lewis and 
Samuelsson have suggested. 
As to the Shetlands, the mean pine-pollen percentage is 10 (the figure 
may not be quite reliable owing to the scantiness of pollen in the samples 
analysed). No macro-remains have been found, and the question as to the 
indigenous occurrence of pine in Shetland must be left unsolved. Curiously 
enough, the only account which I have seen of pine-remains from the 
Shetlands is published in the ‘Transactions of the New Zealand Institute’ 
(Speight, 1911). The account must, however, be a mistake. 
Both in S.W. Sweden and Sjælland pine-pollen has been found in old pre- 
boreal gyttjas. As in Scotland, so here, birch-pollen is dominant, but a 
definite birch-aspen period is not clearly to be distinguished. 
LINN, JOURN.—BOTANY, VOL. XLVI, 20 
