again slowly. Tlic aiiliior observed thai llie \vlii1(' petals 

 beeame l)lue wlicii llie Icinix'i'alui'c, in the last i)]iase of the 

 curve, began to fall below the freezing- point. The latter 

 was found to be - 0.8°. 



The same author reported that an onion hulh, exposed 

 to an external temperature of -4° for 7 hours and hard 

 frozen, was found alive. A thermometer previously in- 

 serted in the middle of the onion showed that the tissue 

 had first been subcooled to -3.1'" and that it then fi-oze 

 for 4 hours between -0.7° and -0.95°. According to the 

 author's idea that death takes place when most of the 

 water content is frozen, the death temperature would lie 

 immediately below the freezing temperature registered. 



Walter and Weismann (19oG), in studies on the differ- 

 ence in the position of the freezing i)oint in living and 

 in dead tissue, observed that in the roots of Daucus carota 

 frozen 3 times in succession (lowest temperature reached: 

 -1.28°) more than half of the cells were alive. The tem- 

 perature was read on a thermometer inserted in the mate- 

 rial, and the loss of vitality was ascertained by the stain- 

 ability of the tissue with eosin. In another series of 6 

 successive freezings of the same object, the lowest tem- 

 perature reached having been - 1.50°, a number of cells 

 were still alive. But repeated freezing, even at tempera- 

 tures becoming gradually higher in the successive experi- 

 ments, resulted in an increased number of dead cells. 



According to Apelt (1909), the death point of potato 

 shoots lies between -2.16° and -2.74°. (For the details 

 of the experimentation see, above, the description of 

 Apelt 's work on potato.) 



Maximow (1914) found that in the root of the red hect, 

 where death was diagnosed by the release of the pigment, 

 the freezing point lay at about -2°, the death point at 

 about - 3°, while ice continued to form, after death, at 

 lower temperatures. (The experimental procedure has 

 been described under the heading "Tuberous Tissue.") 



According to Harvey (1919), leaves, petioles or stems 

 with waxy epidermal coverings resist lower temperatures 



