260 



Mez applies his theory to llic ex])l;niation of various 

 observations or assumptions on the Ix'havior of phmts 

 at low teniix'ratures. Adaplalioii 1<» cliniatG would con- 

 sist in a change of the specific mi 11111111111. The resistance 

 of plants which stay alive in ice would be partly attrib- 

 utable to the fact that the heat developed during ice for- 

 mation protects them and retards the drop of the tem- 

 perature to the specific mininnini. Subcooling might then 

 be rather harmful, as has been said in the preceding cha])- 

 ter. The injurious effect of rapid thawing is explained on 

 the assumption that if the heat necessary to melt the ice 

 be withdrawn too suddenly from the regions surrounding 

 the thawing spot, the temperature of the internal por- 

 tions of the material may be lowered to the specific min- 

 imum. To confirm this interpretation Mez says that, 5 

 mm. below the surface of a frozen apple thaw^ed by the 

 warmth of the hand, he could measure a lowering of tem- 

 perature of 1.8 degree. 



The idea that each animal or plant species is charac- 

 terized by a given death temperature appeals to those 

 biologists who are in quest of shai'])ly defined, typical 

 physical processes. It suggests that death might l)e cor- 

 related w^itli some physical change, which would take 

 place at a definite temperature, as is the case for melt- 

 ing. Apelt (1907) seems to have followed this line of 

 thought. He evidently assumed that the death tempera- 

 ture of a plant species could be measured with the same 

 precision as a melting point when he claimed to have 

 established the range of death temperatures in some 

 types of potato within 0.007 degree. His procedure con- 

 sisted in exposing potato to a given temperature and diag- 

 nosing death by the change in color of the tissue and 

 by the failure of the cells previously stained with methy- 

 lene blue to plasmolyse. 



While Apelt 's precision has not been taken seriously 

 by all biologists, several points in his argumentation and 

 experiments deserve mention. He established, for ex- 



