FROZEN PLANT-ORGANS. 499 



frequently. If the cutting of coppice is delayed in the spring, 

 the annual shoots may not be completely lignified before they 

 are exposed to early frosts. The underwood in coppice-with- 

 standards suffers less than simple coppice, owing to the shelter 

 afforded by the standards. The various shelterwood systems 

 constantly afford shelter to young growth, and are therefore 

 less liable to danger from frost, than the systems of Coppice 

 and of Clear-cutting in High Forest. 



e. Age of Wood. 



Woods are most exposed to danger in youth, especially 

 during the sprouting of the seed ; a single frosty night at this 

 period may at once annihilate the results of a forester's care. 

 The chief danger continues until the young plants have grown 

 above the local frosty zone. As, however, this varies accord- 

 ing to the configuration of the ground, a scale of susceptibility 

 for each species, according to age, cannot be attempted. 



Quick-growing species in breezy hilly localities are most 

 favourably situated, while slow-growing tender plants in valleys 

 and plains suffer most. 



In the case of widely-spread frosts and exceptionally low 

 temperatures, the leaves and shoots of taller trees may suffer. 



f. Locality. 



The following localities are specialty liable to injuries by 

 frost : 



i. Damp, low-lying places with stagnating air, for instance, 

 narrow, closed-in valleys, or small depressions in the ground, 

 termed frost-hollows. In such places, frost-hardy species such 

 as hornbeam, aspen, and birch are naturally invasive, whilst 

 the more valuable species become stunted, and there is gene- 

 rally a plentiful coating of lichens on the trees. If, in such 

 depressions, the soil is moist or wet, or there are water-courses 

 or swamps near at hand, the evaporation of the water still 

 further reduces the temperature, whilst owing to the absence 

 of air-currents the cold air is not replaced by warmer air from 

 the neighbourhood. If, on the contrary, the soil is dry, the 

 plants become cooled by their own radiation, and by the 



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