6] FOUNDATIONS OF MODERN DISTRIBUTIONS l8l 



W. C. Darrah. Principles of Paleobotany (Chronica Botanica, Leiden, 



Holland, pp. [vi r] 239, 1939). 

 R. F. Flint. Glacial Geology and the Pleistocene Epoch (Wiley, New 



York, pp. xviii + 589 & maps, 1947). 

 R. F. Flint. Glacial and Pleistocene Geology (Wiley, New York, pp. 



xiii -|^ 553 and 5 additional maps, 1957). 

 S. A. Cain. Foundatio?is of Plant Geography (Harper, New York & 



London, pp. xiv + 556, 1944) ; for a philosophical discussion of 



the origin and history of plant types and areas. 

 G. L. Stebbins. Variation and Evolution in Plants (Columbia University 



Press, New York, pp. xx + 643, 1950). 

 Nicholas Polunin. Arctic Botany, vol. I : Exploration, Taxonomy, 



Phytogeography (Oxford University Press, London etc., in press) ; 



for application to the northern regions of the world. 

 H. Godwin. The History of the British Flora (Cambridge University 



Press, Cambridge, Eng., pp. viii 4- 384 and additional table, 1956) ; 



for application of recent stages to a more limited area. 



An interesting instance of protracted persistence after introduction was 

 noted by the present writer in 1936 in southwestern Greenland, where he 

 discovered living descendants of plants which had evidently been intro- 

 duced from North America by the Norsemen whose Greenland settle- 

 ments are known to have died out several centuries ago. As certain of 

 these plants are of known but restricted (in two instances barely over- 

 lapping) distribution on the eastern North American seaboard, they give 

 a clear indication of where their ancestors probably came from, and where, 

 accordingly. Viking relics should be sought which would prove once and 

 for all that North America was known to Europeans long before the birth 

 of Columbus. 



In connection with the wide acceptance of sub-fossil pollen grains as 

 evidence of former climates, the author cannot forget that through much 

 of the summer of 1950 he found the most plentiful pollen in the air near 

 the ground in West Spitsbergen to be that of Pinus sylvestris, the nearest 

 trees of which were growing on the Scandinavian mainland several 

 hundreds of miles away to the south. This indicates the need for caution 

 in interpretation — including the desirability of statistical comparisons 

 and, above all, avoidance of any tacit assumption that a small deposit or 

 reasonable amount of an airborne pollen was necessarily produced locally. 



