Cold-Resistance in Spineless Cacti 



139 



perature. With this it was easily possible to study the changes 

 taking place in the protoplasmic cells at the low temperature noted. 

 Ice, in the form of both needle and disk-shaped crystals, was first 

 observed to form on the walls in the intercellular spaces between 

 the cells and above them. When the freezing mixture was removed 

 and also the small pieces of cotton from the openings, the ice that 

 had formed in the intercellular spaces melted gradually, and prac- 

 tically all the water resulting was absorbed again by the cells. With 

 the low temperatures no movement of the protoplasm could be seen, 

 but with the gradual rise of temperature following the removal of 

 the bits of cotton and the freezing mixture, a slow movement of 

 the protoplasm was observed, which became faster with the rise 

 of temperature of the slide. This experiment was repeated several 

 times with the same section of tissue without killing the protoplasm. 



•»>«»l>f*w--: ■'• 



Fig. 10.- 



"Apparatus uted fcr studying the effects of low temperatures and of freezing on 

 the Drotoplasm of cacti. 



The same results were obtained by putting parts 

 stems in test tubes at temperatures slightly below 

 point of water. This was repeated several times, 

 sections in each instance to come to the temperature 

 without injuring the protoplasm. These experiments 

 the protoplasm in the cells of the cacti was not injured (1 

 result of the separation of at least a large part of the 



of the cactus 

 the freezing 

 allowing the 

 of the room, 

 proved that 

 ) either as a 

 water from 



