154 Missouri Agr. Exp. Sta. Research Bulletin No. 8 



mediately frozen, would actually withstand more cold than the 

 hardier red cabbage when frozen in winter. Maximow concludes 

 that the part of the cell which is injured when exposed to low temper- 

 ature is the plasma membrane, and that as long as a film of water 

 was kept in contact with this membrane, death was not likely to occur 

 His theory then would not be greatly different from that of Miiller- 

 Thurgau and Molisch, that withdrawal of water kills, except that in 

 Maximow 's opinion killing following the withdrawal of water seems 

 to be limited to the plasma membrane. 



If Maximow 's work is verified by further experimenting, using 

 other plants, it is certainly a very interesting contribution toward 

 determining just what freezing to death of plant tissue is. 



Mez^ studied the effect of supercooling upon plant tissue. He 

 finds that where ice formation begins at once on reaching the freezing 

 point, the killing is not so great as where there is supercooling when 

 large masses of ice are formed rapidly after crystallization begins. 

 By use of the thermo-couple he studied the fall of temperature in the 

 plant, using stems of Impatiens to determine the eutectic points 

 of the sap solutes. At each of these points there will be a halting 

 in the temperature fall due to the heat given off on crystallization. 

 From this work he concludes that when a temperature of -6 is 

 reached, all solutes will crystallize out. He thinks this should dis- 

 prove the theory of Miiller-Thurgau and Molisch, since there should 

 be complete loss of water at this temperature and the plant should 

 never survive a lower temperature if loss of water from the cell is the 

 cause of death. He holds that the heat liberated by the crystallizing 

 of the solutes and the formation of ice, will after the cells are insulated 

 by the ice mass, aid in keeping the temperature of the cell above 

 that of the surroundings. He holds, therefore, that each plant has 

 its specific minimum point at which death occurs due to the direct 

 effect of the cold, and that if supercooling takes place, large amounts 

 of heat are lost before the cells are insulated by the ice mass and 

 therefore this specific minimum will be more quickly reached. The 

 work of Miiller-Thurgau^ and of Voigtlander^, (a pupil of Mez) 

 where plants supercooled to below the killing temperature remained 

 alive if ice did not form, certainly refutes the theory of Mez. If 

 further evidence were needed, the protective action of organic and 

 inorganic substances shown in Maximow 's work certainly proves the 

 fallacy of Mez's conclusion. Even his conclusion that the sap solute 



iPlora, Vol. 94, p. 89. 1905. (Blbl. No. 74). 



'Landw. Jahrb. Vol. 15, p. 453, 1886-. (Bibl. No. 78). 



'Beitr. z. Biol, der Pfl. Cohn. Vol. 9, 1909. pp. 359-414. (Bibl. No. 110), 



