198 INJURY, RECOVERY, AND DEATH 



each cell forms a thin layer, which surrounds a large 

 central vacuole filled with cell sap. When tissue (either 

 with or without previous treatment with liquid air) is 

 ground with powdered quartz (so as. to open the cells) and 

 a little sea water is added, and the juice is subsequently- 

 expressed, it is found to have a little higher conductivity 

 than sea water. Since this expressed juice consists to a 



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Fio. 87. — Cross section of Laminaria agardhii. (X 150). 



considerable extent of cell sap we may conclude that the 

 conductivity of the sap does not differ very much from 

 that of sea water. The fact that the conductivity is 

 higher, may be due in part to evaporation during the 

 manipulation. When the juice is obtained by merely 



