MICROPALÆONTOLOGY OF POSTGLACIAL DEPOSITS. 483 
1 Polypodium vulgare spore. The gyttja (B) is richer in pollen : 97 birch, 
1 elm, 2 pine, and 1 hazel pollen-grains being counted. Layers C and D are 
very poor in pollen and have not been analysed. 
In the brackish water of Loch Stenness, near P.O. 27 at Waith Bridge, 
a stinking mat of alge (brown, red, and green) was floating along the shore, 
showing that the process of putrefaction is still going on in these layers ; 
but, even so, owing to the chemical composition of pollen-exine, we should 
expect that it would be able to resist decomposition. In that case we should 
expect to find a recent tree-pollen spectrum, formed by pollen which 
could have been transported by wind from a considerable distance. Two 
samples were collected and carefully examined, but no pollen, either of trees, 
shrubs, or herbs, was found. 
Prat Mosses Nos. 28 a and b. 
The slopes of. Wideford Hill (225 m.) W. of Kirkwall are covered here 
and there with sballow peat. In a section (60 cm. deep) a little N.E. of 
the top, three samples were collected and analysed (28 a). 
Sample 1 (5 em. below the surface): 6 Betula; 108 Ericaceæ tetrads. 
Sample 2 (30 em. below the surface): Ericacex tetrads very frequent ; 
2 Chenopodiace: pollen. 
Sample 3 (55 em. below the surface) : Acer 1 per cent., Alnus 26 per cent., 
Betula 49 per cent., Pinus 13 per cent., Quercus 10 per cent., Ulmus 
1 per cent. ; Corylus 20 per cent. : tetrads of Ericace® and grass-pollen 
were of common occurrence. 
West of the top, N.W. of Smerquoy, E. of Hardhill, 40 m. above 
sea-level, a layer of peat (No. 28 6), 55 cm. thick, covered the sandy sub-soil. 
The pollen-spectrum of the lower sample showed: Alnus 17 per cent., 
Betula 60 per cent., Pinus 14 per cent, Quercus 9 per cent.; Corylus 
12 per cent.; Ericaceæ tetrads common ; a single Chenopodiaceæ pollen. 
Thus there is a rather close resemblance in pollen character with the 
bottom layer of 28 a. 
Prat Moss No. 29 (Westray). 
Westray lies most to the north-west of all the Orkney Islands. Peat 
oceurs here only to a very limited extent. Eday, which is said to be fairly 
rieh in peat (cf. Gunn, 1910), unfortunately could not be visited. Natural 
woods are absent from Westray ; only in the neighbourhood of Finbo were 
there planted trees (Acer) and bushes. A wet meadow with Eriophorum 
polystachion, Hydrocotyle, Ranunculus acris, Rumex Acetosella, ete., was 
investigated. It lies between the Bay of Tuquoy and Swartmill Loch, about 
1 m, above high-water mark. The section was only 87 cm, thick, consisting 
of 84 em. of a dy-like substance with rhizomes, and 3 em. clay-gyttja 
resting on sand. 
