THE FLORA 403 



magical rapidity of appearance of vegetation and of flowers, 

 almost coincident with the disappearance of the snows. 

 Hardly does the ground become clear of snow before 

 flowers are there in its place. Not only is there barely 

 any transition between winter and spring, but all kinds of 

 flowers follow upon one another so quickly that spring, sum- 

 mer, and autumn are all rolled into one quickly coming and 

 quickly disappearing, brief, brilliant, and glorious summer 

 season. This is the main factor that introduces a difference 

 into the floral character of different latitudes. In all of 

 them the same conditions are present otherwise, the ex- 

 posure to winds, the coldness of the soil, and other influences 

 that conduce to physiological dryness, but the season 

 grows shorter as one advances farther north, and high 

 latitude will thus conserve more and more the plants of 

 the spring-blooming type, that prepare their blossoms and 

 growths a season beforehand, and tend to exterminate 

 those that come more slowly to maturity. In some places 

 plants relatively unfitted will survive, but will lose some 

 of their characteristics as the season of growth becomes 

 shorter. Thus, Rubus Chamcemorus and Rubus arcticus, 

 which are abundant and fertile in Newfoundland, the writer 

 found to be much more rarely fertile in Labrador and to 

 increase in rarity toward its northern extreme; and it is 

 said that R. Chamcemorus survives, but is without flowers, 

 at its most northern station. In some cases the length of 

 the season suffices for flowers, but not for fruits and seeds. 

 In such cases it would seem to be, not the temperature 

 itself, as Schimper puts it, but the length of time during 

 which the warmer temperatures persist, that determines 

 the surviving species and their reproductiveness. 



