CH. IX.] DEATH AND DECOMPOSITION. 319 



to avoid such circumstances, is by so much to render 

 plants capable of enduring our climate. 



First. Moisture renders a plant susceptible of 

 cold. Every gardener knows this. If the au' of his 

 green-house be dry, the plants -within may be sub- 

 mitted to a temperature of 3-2=^ without injuiy, 

 provided the return to a higher temperatm'e be 

 gradual. 



Secondly. Gradual decrements of temperature are 

 scarcely felt. A myrtle may be forced, and sub- 

 sequently passed to the conservatoiy, cold pit, and 

 even thence to an open border, if in the south of 

 England, -without enduring any injury fi'om the cold 

 of winter, but it would be killed if passed at once 

 from the hot-house to the border. 



Thirdly. The more saline are the juices of a 

 plant, the less liable are they to congelation by 

 frost. " Salt presences vegetables from injury by 

 sudden transitions in the temperature of the atmo- 

 sphere. That salted soils freeze with more reluctance 

 than before the salt is apphed is well known, and 

 that crops of turnips, cabbages, cauliflowers, &c., are 

 similarly preserved, is equally well established a. 



Fourthly. Absence of motion enables plants to 

 endure a lower degi'ee of temperature. Water may 

 be cooled down to below 3-2o without freezing, but it 

 solidifies the moment it is agitated. 



* Cuthbert Johnson on Fertilizers, 381. 



