500 MR. G. ERDTMAN: STUDIES IN THE 
regional history of the forests of southern Sweden in postaretie time), ibid. 
Bd. 48, 1924. Investigations have also been carried out by the disciples of 
von Post. As one of these, I would here express my best thanks to Dr. von 
Post, to whom I am greatly indebted, not least for the interest he has shown 
in the plan of my researches in Scotland. 
As the two leading authorities on the study of micro-fossils (and especially 
of fossil pollen-grains), upon which von Post's method of pollen-analysis is 
based, we must mention Prof. Dr. C. A. Weber of Bremen and Prof. Dr. G. 
Lagerheim of Stockholm. The former as early as 1893, in his paper “ Ueber 
die diluviale Vegetation von Klinge in Brandenburg und über ihre Herkunft ” 
(Engler's Bot. Jahrbücher, xvii. Beibl. 40), counted pollen-grains and ealeu- 
lated the proportion between Pinus and Picea pollen. He laid stress upon 
the suggestion that pollen-grains must, on the average, give a truer picture 
of general vegetation of a neighbourhood than the remains of wood and 
fruits, for the occurrence of these in the water depends on chance (l e. p. 8). 
Prof. Lagerheim has carried out a great number of important and most accurate 
enumerations of pollen-grains, and has studied the occurrence of other micro- 
fossils, especially parts of eryptogams. Also he has made miero-analyses 
from Scottish peat deposits, the results of which are published in the work of 
Samuelsson : * Scottish Peat Mosses " (Bull. of the Geol. Inst. Uppsala, vol. x. 
1910). Because of his remarkable knowledge of micropaleontology, 
Dr. Lagerheim has for many years been able to help and encourage many 
peat geologists. He has also done much towards perfecting methods of 
analysis. For several years I have had the opportunity of working at the 
Botanical Institute of the University of Stockholm under the direction of 
Prof. Lagerheim ; also a short time ago (Easter 1923) I visited Prof. Weber 
in connection with some peat investigations in North-West Germany. To 
both of them I express my respectful thanks. 
To Mrs. E. M. Reid, Milford-on-Sea, I remain especially indebted for 
having most kindly undertaken the correction of my English. 
To Dr. J. Horne of Edinburgh I am greatly indebted for invaluable help 
in the way of good advice and the kind loan of geological maps. For help 
in various forms I have also to thank Dr. A. Gravelin, Head of the Geological 
Survey of Sweden, Dr. J. Gunn of Edinburgh, Mr. D. Mackenzie of 
Stornoway, Prof. P. Quensel of Stockholm, Dr. E. J. Salisbury of Radlett, 
and Prof. Sernander of Uppsala. G. ERDTMAN. 
The Botanical Laboratory, 
The University, Stockholm. 
Dee, 29th, 1925. 
