Section first 



PROTECTION OF FORESTS AGAINST INJURIES DUE 

 TO INORGANIC AGENCIES. 



CHAPTEE I. 



DAMAGE CAUSED BY Low OR HIGH TEMPERATURE. 



A. FROST. 

 5. Different kinds of Frost, and their Injurious Effects. 



Under frost generally is understood any sinking of the tem- 

 perature below the freezing point ; but in regard to the time at 

 which it occurs, a distinction is made as to late frost, early frost, 

 and winter frost, whilst in respect to the peculiar way in which it 

 is occasioned by winter and late frosts, freezing and lifting of the 

 soil will be treated of in a paragraph by itself. 



Under Late or Spring Frosts are understood those depressions 

 of temperature below the freezing point, which take place in 

 portions of plants after the entry into the period of active vege- 

 tation in spring. They kill the tender young shoots, leaves, and 

 flowers that may have opened, these becoming first of all drooping 

 and withered, then assuming a blackish discoloured appearance in 

 consequence of the decomposition of the chlorophyll, and finally 

 falling off. Seedlings just germinating are usually completely 

 killed, whilst stronger plants are interfered with in growth by the 

 loss of their young shoots, or are finally completely deformed by 

 repeated recurrence of the damage. The prospect of a seed year 

 can be obliterated by the destruction of the flowers, and the 

 regular progress of natural reproduction can thus be not incon- 

 siderably interfered with. From obvious causes, the increment 

 on damaged plants and trees is smaller than usual in years when 

 late frosts have been bad. 



