THE FLORA 397 



the vegetation are protections not against cold, but 

 against dryness. Even with an abundance of moisture in 

 the soil, it may not be readily available for the plant. The 

 soil is cold, the bogs are rich in humous acids, the water of 

 the shores is full of soluble salts. All these conditions, 

 which are the prevailing ones throughout the northern 

 country, are unfavourable to the ready absorption of water 

 by the plant, and hence lead to physiological dryness. 

 This is further increased by the lack of protection against 

 drying winds, which tend to produce strong transpiration. 

 A plant whose water supply is limited, whether in wet or in 

 dry soil, must guard against too great transpiration, espe- 

 cially under conditions where this tends to be large. It 

 hence assumes a xerophilous structure, or one fitted to con- 

 tend with physiological dryness. In this respect the flora 

 of Arctic climates, of alpine heights, of bogs, of sea-shore, 

 and of deserts will closely resemble one another, though the 

 particular devices adopted may vary with different con- 

 ditions. 



Except hi the rarer situations of sheltered valleys or 

 sunny slopes, with relatively warmer soil, water free from 

 acids, and protection from wind, the flora of Labrador may 

 be considered as universally adopting one form or another 

 of the various means fitted to protect it from too great 

 dryness. It becomes an absorbingly interesting study to 

 observe the different ways in which this object is accom- 

 plished. The most evident devices are the following : 



1. A well-developed system of roots for the absorption 

 of nutrient materials and of water. 



2. A low and often stunted growth. This characteristic, 

 as a special modification, applies of course to plants that 



