491 



CHAPTEE I. 



PROTECTION AGAINST FROST. 



As regards its distribution, frost may be either widespread 

 or local ; as regards season, early frosts occur in the autumn 

 and late frosts in the spring. Early or late frost may be 

 either widespread or local. Late frosts are commoner in 

 Europe than early frosts, and occur chiefly in lowlands, early 

 frosts being more prevalent in mountainous regions. The 

 extensive damage done by late frosts is due not only to their 

 frequency, but also to the susceptibility of plants during the 

 revival of vegetation in the spring. Frosts in May are usually 

 most fatal, June frosts being rare. April frosts are less 

 dangerous, vegetation not being sufficiently advanced to suffer 

 greatly. In the North-West of India, early frosts usually 

 do most damage, as the bright days and cold nights of 

 November sometimes involve daily ranges of temperature 

 of 40 and even 50 F., that are fatal to the sappy shoots 

 of trees. 



Wintgr-frosts in Europe rarely injure indigenous trees, 

 though they may kill unprotected exotic evergreen plants 

 such as laurels, etc. The mild winters experienced in the 

 west of France and of the British Isles, render possible the 

 outdoor cultivation of many plants whose natural habitat 

 is further south, and which would succumb to the severe 

 winters of more easterly European countries, as was the case 

 with the common gorse, and many exotics, in Surrey, in 

 1895. Seeds have been subjected to temperatures of liquid 

 air (180 C.) for 110 hours without injury, germinating just 

 as freely as other test seeds not so treated (Mr. Horace Brown 

 and Prof. Dewar, 1897). 



Frost damages forest-plants in four ways : 



i. By freezing to death young woody plants or young 

 organs of plants. 



