202 DORIS LOVE 



distribution areas (Jeffre, 1960). Even the average air temperature of the 

 summer months may not give a full answer to the tolerance of a given species. 

 Under conditions which may seem forbidding to a human, a microclimate 

 may exist that is very tolerable for a plant (Monteith, 1960). Floras, from a 

 dozen to well over a hundred species, exist today in areas where the tempera- 

 tures at meteorological stations indicate averages only slightly above the 

 freezing point throughout the growing season (cf. Fristrup, 1952, for Peary 

 Land, Greenland: June 2.6°, July 6.3°, Aug. 3.6^C; Aleksandrova, 1961, for 

 Great Lyakhovsky Island, N. of Siberia: June 0.2°, July 3.5°, Aug. 2.5°C; 

 Savile, 1961, for Isachsen, Queen Elizabeth Islands, Canada: June 0.38°, 

 July 3.5°, Aug. 1.25°C). 



Aleksandrova's (1961) detailed analysis of the phenology of Great Lyak- 

 hovsky Island in the Novosibirsk Archipelago in the summer of 1956 demon- 

 strates the close relationship between temperature at ground level and plant 

 development, and shows that even in this rigorous climate a rhythmic and 

 seasonal development of the flora takes place. During the short vegetative 

 season, thus, both Ranunculus sulplmreus and R. Sabinei had two different 

 flowering periods, a spring anthesis 23 June to 25 July and a fall anthesis 

 8 Aug. to 20 Aug., both apparently temperature-regulated. She noticed a 

 difference also in the rhythmic development and length of the vegetation 

 periods between various plant communities. The ones on the quickly thawing 

 and warming polygon-tundra were richest in species, first to start growth, and 

 first to reach a fall aspect, whereas communities in depressions with a long- 

 lasting snow-cover, in spite of starting vegetative development under the 

 snow, were slower in maturing and had shorter, more compressed seasons, as 

 well as a lesser number of species. 



Tikhomirov, Shamurin and Shtepa (1960) have recently used micro- 

 thermo-couples to measure the temperature in various parts (buds, leaves, 

 stems, roots, etc.) of Arctic plants (e.g. Sieversia glacialis in E. Siberia), and 

 found their temperature to be up to several degrees (Centigrade) higher than 

 ihe surrounding air temperature. The differences were most marked on clear, 

 quiet days, but noticeable also on overcast and windy days. It is interesting 

 that the roots, too, had higher temperatures than the soil around them. 



At high altitudes in the Himalayas (Swan, 1961) it has been demonstrated 

 that a favorable microclimate and access to some water will permit wind- 

 dispersed plant species to take hold, even where the success seems bleak 

 indeed, judged by human standards. 



A high degree of adaptation against climatic rigors: polster-growth, much 

 hairiness, dark buds, characters which we regard as "protective measures", 

 are of course often found among plants thriving in our area. But there are 

 also several plants which lack these qualities and still survive well (cf. Bocher, 

 1938; Sorensen, 1933). 



It is, however, easily forgotten that these same plant species, subjected lo 



