EFFECT OF FROST ON PLANTS. 65 



som and young fruit without any damage. In re- 

 gions where there is no frost, the orange tree, when 

 sufficiently fed, is in the habit of fruiting continu- 

 ously. 



When water freezes it expands. It is owing to 

 this law that cold is so fatal to plants fully charged 

 with sap, mainly composed of water. The sap, by 

 expanding, ruptures the cellular tissue the woody 

 cells containing the sap. The oxygen of the at- 

 mosphere penetrates these ruptures, and, combining 

 with the sap, induces fermentation. Unless pre- 

 vented, either by artificial or natural means, this fer- 

 mentation will extend itself to contiguous parts 

 until the whole plant is destroyed, when only a 

 small portion of the tender wood may, in the first 

 instance, have been frosted. Nature's method is 

 to close behind the rupture all avenues against the 

 penetration of the atmosphere by a deposit of glu- 

 tinous or gummy substance furnished by the inner 

 bark. When the old wood or bark decays or drops 

 off, this inner becomes the outer bark, and so the 

 damage is greatly and sometimes wholly repaired. 

 The artificial remedy is to cut off the frosted wood 

 and at once apply an artificial skin impervious to 

 the atmosphere. Many persons who have treated 

 frosted orange and lemon trees have failed at this 

 latter point. They have cut off a part or all the 

 frosted wood, but left a surface to be cracked by 

 the sun or drying of the wood, and so only opened 

 fresh avenues for the penetration of the atmosphere. 



