120 Principles of Plant Culture. 



more injuriously than a severer degree of shorter dura- 

 tion. Prolonged freezing is especially injurious when 

 the frozen parts are subjected to drying wind, which 

 evaporates their water, while the frozen condition pre- 

 vents movement of their fluids. 



d The frequency with which freezing and thawing are 

 repeated. Frequent slight freezing and thawing are far 

 more injurious than a prolonged frozen condition, even 

 though the latter occurs at a much lower temperature. 

 Winter wheat and rye, and strawberry beds are often 

 more damaged in mild winters, in which freezing and 

 thawing weather alternate, than in more severe ones, 

 when the temperature is mostly below freezing. The 

 chief damage is usually done to these crops in late au- 

 tumn and early spring. 



e The previous treatment of the plant. Plants grown 

 by artificial heat may be far less able to endure cold than 

 others of the same varieties grown in the open air, pos- 

 sibly owing to the more succulent condition of the former. 

 Gardeners harden plants grown under glass, by gradually 

 exposing them to the cooler out- door atmosphere, before 

 removing them to the open ground. 



f The treatment of the frozen tissues. Handling plants, 

 fruits or vegetables while frozen greatly aggravates the 

 damage from frost, probably because the handling in- 

 creases laceration of the cells by the ice crystals within 

 them. 



191. Frost-Injured Plants, Fruits or Roots May often Be 

 Saved from serious damage, if promptly placed under 

 conditions that cause the slowest possible thawing of the 

 tissues, as shading from the sun's rays, immersing in ice 



