460 MR. G. ERDTMAN : STUDIES IN THE 
Sequence of strata :— 
A. 100 em. — Carex-Scirpus cespitosus peat. 
B. 275 em. A very thoroughly humified moist substance, most resembling 
a sort of dy. 
^ 125 em. Gyttja. 
D. (at 500 em.). Sand. 
In Scotland one very seldom meets with well-defined contacts between the 
different kinds of peat and mud. In this peat moss, as in most others, there 
is a gradual passage from one kind of peat or mud to another. 
If pollen-diagrams are compared with one another, the greatest caution is 
necessary when trying to synchronize a layer in one peat moss with a layer 
in another, unless the evidence is based on more than a resemblance in the 
Form of the pollen-curves (ef. Erdtman, 1921, p. 24). In the present case, 
however, the layer from whieh sample 6 is taken shows so conspicuous a 
resemblance in its pollen-flora to the A-zone of peat moss No. 1, that they can 
scarcely be other than synchronous. Another resemblance lies in the fact 
that the PF is greatest in this layer in both peat mosses. Thus it is evident 
that the formation of peat in No. 1 first began when the formation of gyttja 
in No. 2 had ceased, and the lake which had formerly occupied the site had - 
been silted up. 
Pollen of Tilia occurred in sample 3, and that of Myriophyllum alterniflorum 
in the three gyttja samples (frequency small, maximum 3:3 per cent. in 
sample 9). 
Prat Moss No, 3. 
TRXT-FIG. 3. 
0 10 20 30 40 50 60 70 80 90 100 % 
— ot EE 
2- = 
—0— Alnus. —O— Betula. —9— Pinus, nn Uimus. 
Quercus. ------.. Tilia, --m-- Corylus, 
