MICROPALZONTOLOGY OF POSTGLACIAL DEPOSITS. 485 
willows found elsewhere in the district. As Myriophyllum alterniflorum 
pollen is often abundant in such silty layers, a careful examination should 
yield the fruits of this species. Fossil fruits are described by G Anderson, 
H. A. Weber, and others. In layer 3 the Calluna stems were found to be 
much shrunken ; frequently the interior of the stems had disappeared, 
leaving only the epidermis. As this layer was traced along the banks of 
streams, it was found to be of unequal thickness. It would appear, therefore, 
that it marks a period of denudation during which the surface of the bed 
became wasted and channelled into peat-hags like those met with on the 
present surface of the moss. 
In his Part III. 1907, p. 56, Lewis lays stress upon the circumstance 
that there must have been considerable climatic changes in postglacial 
time: “The presence of a buried forest on the west Shetland coast below an 
Arctic bed shows that the Atlantic cyclones must have pursued an entirely 
different path when that forest spread over the country, for the most 
favourable conditions of soil and temperature would not permit forest under 
present climatic conditions, and indeed a more unfavourable position for tree 
growth could hardly be found at the present time in North-West Europe.” 
As to macro-palæontological evidence of the presence of postglacial 
woodlands in the Shetlands, Lewis found remains (referred to the Lower 
Forest) of birch, alder, rowan, also of hazel and sweet-gale (iii. p. 52 : 
iv. p. 801). Remains of an Upper Forest were not found. In the Isle of 
Foula there occurred, however, a juniper-bed, possibly belonging to the 
Upper Forest ; also from the mosses of the Faroe Islands fossil juniper has been 
described (Ostendfeld, 1901; Jessen and Rasmussen, 1922). Lewis did not 
meet with macroscopical pine-remains, but he found pine-pollen in a section 
between Stourborough Hill and Sandness Hill; this oceurred in silt with 
Equisetum, which occupicd the interstices between the stones at the bottom of 
the section. He does not consider, however, that these pollen-grains show 
that pine was ever native in Shetland, because of the distance (in this case 
“ at least many hundred miles ”) over which pollen may be carried by wind, 
In the western part of the Shetland mainland, in the parish of Walls- 
Sandness, three peat-deposits along the road between Melby and Bridge of 
Walls were investigated (peat mosses Nos. 24-26), all characterized by the 
scantiness of fossil-pollen. 
Prat Moss No. 30. 
Situated above 90 m. above sea-level on the watershed, Sound of Papa- 
Gruting Voe, near point 309 west of Mousavord Loch and a little east of 
the above-mentioned Sandness road. 
Stratification :— 
A. 150 cm.  Æriophorum vaginatum peat; T5 em. H<6; then 75 em. 
H>6. 
