290 TYGE W. BOCHER 



Greenland is perhaps more a result of climatic oceanity which prevents tree 

 growth but does not present any obstacles for such forest floor species as 

 Coptis trifolia, Pyrola minor, Orthilia secunda ssp. obtusata, Linnaea borealis 

 ssp. americana, or a Boreal muskeg species such as Ledum groenlandicimi. 



The two hues in Fig. 2 (on the right) connect points (local floras) with more 

 than 25 per cent Oceanic-sylvicolous species (western line) and more than 25 

 per cent Continental species (eastern Hnes). South of Holsteinsborg these two 

 curves overlap but they diverge northwards in the inland archipelago of 

 Nordre Stromfjord where the mountains are lower and the oceanic air 

 masses sometimes are able to penetrate into the inland areas (Bocher and 

 Loegaard, 1962). 



The old question about the occurrence of American and Eurasiatic flora 

 elements in Greenland was recently considered (Bocher, Holmen and Jacobsen, 

 1959; Lindroth, 1960; Bocher, 1963). How to classify eastern and western 

 species is always a matter of opinion because some of them are Amphi- 

 Atlantic but with almost equally large areas on both sides. In such cases, 

 however, an increased variability on one of the sides may give additional 

 valuable criteria. But, although some of the species tabulated as eastern or 

 western were removed, the material is sufficient to show that European 

 plants play a subordinate role in all parts of Greenland except southeast and 

 middle east Greenland where western and eastern species are present in 

 almost equal numbers, although not with the same frequency. The eastern 

 species are obviously more abundant (Bocher, 1938), a fact which has a 

 connection to their climatic requirements. Most of the eastern plants are 

 clearly montane North Atlantic (sometimes also North Pacific) and absent 

 from the driest tundra areas of northernmost Asia and Canada. Ecologically 

 they demand snow in great quantities and high humidity. Such conditions 

 are found in the Alps, Norway, Scotland, the Faeroes, Iceland, and the 

 southern part of Greenland (except for certain inland areas). These species 

 have been able to migrate from Europe to North America via the Atlantic 

 islands which are washed or influenced by the Gulf Stream and therefore 

 have a suitable climate. On the other hand, the majority of American species 

 require a continental chmate. They occur in north Greenland and southwards, 

 mainly inland. The American species came mostly from Arctic-Continental 

 areas and hence many of them were unable to penetrate to south Greenland 

 with its maritime chmate. Some of them (11 per cent) were High Arctic and 

 were able to reach east Greenland through the north Greenland barrens. 



This diff'erent behavior of western and eastern species in Greenland is 

 evidenced through the calculations summarized in Table 1. Most important is 

 the fact that U-distributions (W.-S.-E.) are most frequent among the European 

 species and (l-distributions (W.-N.-E.) among the American species. 



There are, of course, deviations. Thus, Braya linearis, Draba sibirica, and 

 Fotentilla stipularis exemplify eastern species which have reached continental 



