EFFECTS OF COLD 97 



end, with the result that the entire plant is 

 reproduced within a short period. Some 

 species form a hibernaculum at the tip of each 

 branch, with the result of multiplying the 

 plant by this method. 



Some plants as a whole avoid low temper- 

 atures by growing in such a manner as to be 

 covered with a protecting blanket of leaves 

 and snow ; and others retire to a depth below 

 the frost line in the medium in which the3^ live. 



Winter buds are of course devices for the 

 protection of growing tips against sudden 

 changes of temperature and moisture, as well 

 as from mechanical injuries due to wind, sleet, 

 snow or ice. 



As a conclusion to be derived from the fore- 

 going paragraphs it is to be seen that proto- 

 plasm seeks to avoid danger of disorganiza- 

 tion from the formation of ice in its interstices 

 by getting rid of a portion of its water when 

 the temperature falls, and the death of a plant 

 does not necessarily follow "freezing." Death 

 by cold may be due to the direct action of 

 cold, or to the consequent desiccation of 

 the tissues. When due to the latter cause it 

 may be brought about by temperatures above 

 the freezing point. 



That temperature has been a most impor- 

 tant factor in the evolution of the vegetable 

 kingdom, as well as in the distribution of the 



