Plants of Different Regions. 343 



winter night and long summer day, and its cold, dry winds. 

 During the winter night, the land is shrouded in ice and 

 snow which is frequently not sufficiently melted for vege- 

 tation to appear before about the first of July. July, which 

 has an average temperature varying in different localities 

 from 3.8° C. to 8.8° C. (38.8° to 47.8° F.), and even rising 

 as high as 13.4° C. (56.1° F.) at Ustjansk, is the warmest 

 month. The sun is entirely above the horizon for 65 days 

 in latitude 70°, and for 134 days in latitude 80°, and, during 

 part of these periods, the sum of the sun's energy avail- 

 able to plants for each twenty-four hours may be even 

 greater than the available amount at the equator at the 

 same time. Because of the cold, the shortness of the 

 vegetative period, and the dry winters, trees are able to 

 make only a feeble growth, and they do not exist far 

 beyond the arctic circle. 



About the first of July, when the snow and ice have 

 melted in places, and sufficient heat has accumulated in 

 the soil, vegetation in general suddenly starts into new 

 growth. Kjellman, the botanist of the Vega Expedition, 

 says of the beginning of the vegetative period within the 

 arctic circle : " It is here not the same as in the more 

 southern latitudes, where one species after another grad- 

 ually comes to maturity. In the high north there are no 

 spring, summer, and autumn floras composed of various 

 plants blooming at different times, as farther to the south ; 

 in the polar regions everything, or nearly everything, 

 springs into life at once ; development begins everywhere 

 at the same stage and proceeds with equal rapidity, so that 

 all flowering plants are suddenly and at the very beginning 

 of the vegetative period decked in their summer attire." 



The vegetative period lasts only till the end of August, 

 there being but two months of each year during which 



