11 
1915 - 16 .] Opening Address by the President. 
occurrence of two forest beds in our Scottish peat mosses, separated by a 
layer of peat, and with an overlying sheet of peat. He inferred that the 
forest growths indicated dry and continental conditions, while the peat 
layers implied colder and wetter conditions. The botanical evidence was 
subsequently dealt with by Dr Francis I. Lewis, who published the results 
of his detailed investigations in the Transactions of the Royal Society of 
Edinburgh. The various stages identified by Dr Lewis between the south 
of Scotland and the Shetland Isles, and in the Outer Hebrides, are given in 
the following table in descending order : — 
9. Recent peat. 
8. Forest bed. 
7. Peat-bog plants with 
Arctic plants. 
6. Forest bed. 
5. Peat-bog plants. 
4. Arctic plant bed. 
3. Peat-bog plants. 
2. Forest bed. 
1. Arctic plant bed. 
Upper Forestian. 
Upper Peat Bog. 
Second Arctic Bed, 
Lower Peat Bog. 
Lower Forestian. 
First Arctic Bed. 
The First Arctic Bed rests on glacial deposits and yields Salix reticulata , 
S. herbacea, and Betula nana. The Lower Forestian stage is characterised 
by birch, hazel, and alder, with temperate plants. The Second Arctic Bed, 
intercalated in peat, is composed mainly of Arctic plants and is overlain 
by an upper forest, which in the south of Scotland consists of Pinus 
sylvestris, except in Tweedsmuir, where the white birch takes the place 
of the pine. In the Highland areas the upper forest appears as two 
growths of pine, separated by a layer of peat from 1 to 3 feet thick, 
the succession being capped by recent peat. Dr Lewis points out that the 
flora of the two Arctic beds descends to within 150 feet of the sea-level — 
a wide divergence from the present lower limit of Arctic- Alpine vegetation, 
which is about 2000 feet. No trace of Arctic plants has been detected in 
the intervening Lower Forestian zone with a temperate flora. The 
evidence furnished by the forest growths is no less interesting. In the 
Lower Forestian stage the trees rise to 1500 feet, and in the Upper 
Forestian to about 3500 feet, the present upper limit of pine and birch 
being 2000 feet. 
The definite succession of plant remains in the Scottish peat mosses 
confirms the conclusions reached by James Geikie on other grounds. The 
First Arctic Bed marks the passage from the Mecklenburgian Glacial Stage 
