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 Chamemorus 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. Chamemorus survives, but is without flowers, 
at its most northern station. In some eases the length of 
the season suffices for flowers, but not for fruits and seeds. 
In such eases 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. 
