42 STATE POMOLOGICAL SOCIETY. 



the living cells in the outer tissues of the young limbs have been 

 killed that they cannot perform their proper function and death 

 results, either to a part or a whole of the tree, depending on how- 

 many of the limbs are badly affected. 



There is always an upper and a lower limit of temperature 

 that a given species can withstand. Some tropical plants are 

 killed at a temperature of from +35 degrees to +40 degrees F. 

 while some arctic plants have been known to withstand — 60 

 degrees to — 70 degrees F. Our experience during the past 

 season with apple trees shows us that this minimum limit varies 

 with the variety and with the individuals of a given species or 

 variety. When we get down to — 30 degrees or — 40 degrees 

 F. we have come within the danger limit for most varieties of 

 the apple. Last winter the records at Orono show that we 

 reached this limit in January twice within a few days of each 

 other. 



When a tree freezes water is withdrawn from the cell walls 

 and cell sap and forms in crystals in the intercellular spaces or 

 in the interior of the vessels, hence the cell walls become much 

 dryer, and the cell contents, even though they do not freeze 

 themselves, become more concentrated, — a condition similar to 

 drought. If now thawing gradually takes place the water is 

 reabsorbed slowly and the vital functions of the cells are 

 renewed. If on the other hand the frozen tissues are rapidly 

 warmed and the water quickly liberated trouble is sure to fol- 

 low, just the same as will be the case if ihe small boy t^ awt his 

 frosted ears by the kitchen stove instead of using the time 

 honored snowball. 



Before attempting to fix just hozv and zvhen our trees were 

 killed last winter, let me quote three sentences from one and one 

 from another of the best German authorities on this subject, 

 the latter a specialist in the diseases of trees. 



1. "Thawing is more dangerous than freezing, as, if it 

 proceeds too rapidly, it kills more plants and plant parts than 

 extreme cold." 



2. "Those parts of plants that contain little water are par- 

 ticularly endowed with the power to withstand cold." 



3. "Death from cold is undoubtedly in very many cases a 

 result of want (withdrawal or loss) of water and not of low 

 temperature." 



