DISPERSAL AND SURVIVAL OF PLANTS 203 



such cold treatment, have also had to go through a period of considerably 

 higher temperatures than at present, the Hypsithermal. It may be said that 

 the plants have had their tolerances tried to the utmost. 



That many species, which we regard as confined to cold climates, do 

 have an almost incredible tolerance, has been demonstrated to me by some 

 wild plants at present cultivated in our greenhouse at the Montreal Botanical 

 Garden. These plants were brought down from the top of Mt. Washington, 

 New Hampshire, U.S.A., from an altitude of 1918 m and a cHmate with a 

 yearly average temperature of — 2.8°C (July 9.5°C, extremes Jan. — 43.9°C, 

 July 21.7°C). They have been able to survive three years of maltreatment in 

 small pots, scorched by summer temperatures of over 50 °C, erratically over- 

 and under-watered, occasionally frozen, subjected to extraordinary variations 

 in air-moisture, and still they go on existing, growing, and even flowering and 

 fruiting. Among them are such species as Silene acaulis, Saxifraga hyperborea. 

 Campanula dubia, Bistorta vivipara, Juncus trifidus, Hierochloe orthantha, all 

 normally considered as requiring Arctic, or at least High Alpine, conditions 

 for their existence. 



If one dares to judge from the few examples given above, the tolerance of 

 many of the species which grow in the North Atlantic area is very wide 

 indeed. Most likely it is the result of strong selection over a very long period of 

 time. 



The fact that we have a high percentage of polyploids in this flora may 

 also be an indication of its genetical amplitude for varying conditions at the 

 same time as it may possibly indicate its old age (Love and Love, 1943, 1949; 

 Love, 1959). 



In the opinion of this author it seems therefore that, dispersal and survival 

 conditions considered particularly, there are very strong indications that the 

 present native flora in the North Atlantic area is old, well established, and 

 in the majority of cases a relict from a time preceding the Pleistocene Ice 

 Age or at least its latest phases. 



REFERENCES 



Aleksandrova, v. D. (1960). Some regularities in the distribution of the vegetation in the 



Arctic tundra. Arctic 13, 147-163. 

 Aleksandrova, V. D. (1961). Seasonal dynamics of plant associations in the Arctic (in 



Russian). Problem i Severa 4, 59-24. Acad. Sci. U.S.S.R. 

 Beijerink, W. (1947). Zadenatlas der Nederlandschen Flora. Veenman & zonen, Waagenin- 



gen. 

 Bliss, L. C. (1958). Seed germination in Arctic and Alpine species. Arctic 11, 180-189. 

 BocHER, T. W. (1938). Biological distributional types in the flora of Greenland. Medd. om 



Groenl. 106, 1-339. 

 BocHER, T. W., HOLMEN, K. and Jakobsen, K. (1957). Gronlands flora. P. Haase & Sons 



Forlag, Copenhagen. 

 Buss, T.O. (1946). Bird detection by radar. The Auk 63. 315-318. 



