DAMAGE CAUSED BY LOW OR HIGH TEMPERATURE. 9 



them, i.e., the height up to which the cold layers of air, laden 

 with evaporated moisture, and at the same time prevented from 

 circulating sidewards, reach. The more rapidly growing species of 

 trees consequently outgrow the danger from frost earlier than 

 those that develop more slowly. 



The later in spring a late frost occurs, or the more vegetation 

 has developed, the greater is naturally the damage caused ; and 

 frosts which occur about the middle, or, worse still, the end of 

 May, often do an exceedingly great amount of injury in the 

 vegetable world. Late frosts, coupled with simultaneous hoar- 

 frost, are usually more injurious and severer than dry frost ; whilst 

 rapid thawing of the frozen portions, occasioned by the immediate 

 and direct action of the sun after a frosty night, is considered 

 especially injurious, particularly in cases that might otherwise 

 have been of a lighter and less fatal character (see par. 5). 



Broad-leaved trees, that have lost their foliage through late frosts, 

 regain a certain amount of foliage by means of the adventitious 

 buds, but always to a minor extent only, so that the effects of the 

 damage may be noted more or less distinctly throughout the 

 whole of the current year in a degree commensurate with the 

 reproductive capacity of the species concerned, thus the refolia- 

 tion of the Oak is more complete than that of the Beech. Soil 

 and weather are, however, also of influence in regard to the 

 recovery from the effects of late frosts, and the better the soil, 

 or the damper and at the same time the warmer the weather, 

 the more likely the damaged plants are to make a fair recovery. 



The damage caused by occasional early or autumnal frost, 

 occurring before the active period of vegetation is closed and the 

 hardening of the young shoots completed, is always less severe, 

 as only a portion of the young shoots is lost, and neither flowers 

 nor seedlings are affected. The extent of the damage is depend- 

 ent on similar factors as in the case of late frosts, but in coppice 

 woods the time of felling is also of influence, as in Oak coppice a ' 

 late fall in spring delays the flushing of the shoots from the 

 stool, and necessitates the prolongation of vegetation far into 

 autumn, so that the first autumn frosts often find the young 

 shoots at least partially unhardened. The kind of weather in 

 general obtaining during the current year is also of influence, as 

 a cool summer, with a damp and at the same time warm autumn, 

 leads to prolongation of the period of vegetation and consequent 



